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rt-thread/components/external/SQLite-3.8.1/src/where.c

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/*
** 2001 September 15
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements. This module is responsible for
** generating the code that loops through a table looking for applicable
** rows. Indices are selected and used to speed the search when doing
** so is applicable. Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
*/
#include "sqliteInt.h"
/*
** Trace output macros
*/
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
/***/ int sqlite3WhereTrace = 0;
#endif
#if defined(SQLITE_DEBUG) \
&& (defined(SQLITE_TEST) || defined(SQLITE_ENABLE_WHERETRACE))
# define WHERETRACE(K,X) if(sqlite3WhereTrace&(K)) sqlite3DebugPrintf X
# define WHERETRACE_ENABLED 1
#else
# define WHERETRACE(K,X)
#endif
/* Forward references
*/
typedef struct WhereClause WhereClause;
typedef struct WhereMaskSet WhereMaskSet;
typedef struct WhereOrInfo WhereOrInfo;
typedef struct WhereAndInfo WhereAndInfo;
typedef struct WhereLevel WhereLevel;
typedef struct WhereLoop WhereLoop;
typedef struct WherePath WherePath;
typedef struct WhereTerm WhereTerm;
typedef struct WhereLoopBuilder WhereLoopBuilder;
typedef struct WhereScan WhereScan;
typedef struct WhereOrCost WhereOrCost;
typedef struct WhereOrSet WhereOrSet;
/*
** This object contains information needed to implement a single nested
** loop in WHERE clause.
**
** Contrast this object with WhereLoop. This object describes the
** implementation of the loop. WhereLoop describes the algorithm.
** This object contains a pointer to the WhereLoop algorithm as one of
** its elements.
**
** The WhereInfo object contains a single instance of this object for
** each term in the FROM clause (which is to say, for each of the
** nested loops as implemented). The order of WhereLevel objects determines
** the loop nested order, with WhereInfo.a[0] being the outer loop and
** WhereInfo.a[WhereInfo.nLevel-1] being the inner loop.
*/
struct WhereLevel {
int iLeftJoin; /* Memory cell used to implement LEFT OUTER JOIN */
int iTabCur; /* The VDBE cursor used to access the table */
int iIdxCur; /* The VDBE cursor used to access pIdx */
int addrBrk; /* Jump here to break out of the loop */
int addrNxt; /* Jump here to start the next IN combination */
int addrCont; /* Jump here to continue with the next loop cycle */
int addrFirst; /* First instruction of interior of the loop */
int addrBody; /* Beginning of the body of this loop */
u8 iFrom; /* Which entry in the FROM clause */
u8 op, p5; /* Opcode and P5 of the opcode that ends the loop */
int p1, p2; /* Operands of the opcode used to ends the loop */
union { /* Information that depends on pWLoop->wsFlags */
struct {
int nIn; /* Number of entries in aInLoop[] */
struct InLoop {
int iCur; /* The VDBE cursor used by this IN operator */
int addrInTop; /* Top of the IN loop */
u8 eEndLoopOp; /* IN Loop terminator. OP_Next or OP_Prev */
} *aInLoop; /* Information about each nested IN operator */
} in; /* Used when pWLoop->wsFlags&WHERE_IN_ABLE */
Index *pCovidx; /* Possible covering index for WHERE_MULTI_OR */
} u;
struct WhereLoop *pWLoop; /* The selected WhereLoop object */
Bitmask notReady; /* FROM entries not usable at this level */
};
/*
** Each instance of this object represents an algorithm for evaluating one
** term of a join. Every term of the FROM clause will have at least
** one corresponding WhereLoop object (unless INDEXED BY constraints
** prevent a query solution - which is an error) and many terms of the
** FROM clause will have multiple WhereLoop objects, each describing a
** potential way of implementing that FROM-clause term, together with
** dependencies and cost estimates for using the chosen algorithm.
**
** Query planning consists of building up a collection of these WhereLoop
** objects, then computing a particular sequence of WhereLoop objects, with
** one WhereLoop object per FROM clause term, that satisfy all dependencies
** and that minimize the overall cost.
*/
struct WhereLoop {
Bitmask prereq; /* Bitmask of other loops that must run first */
Bitmask maskSelf; /* Bitmask identifying table iTab */
#ifdef SQLITE_DEBUG
char cId; /* Symbolic ID of this loop for debugging use */
#endif
u8 iTab; /* Position in FROM clause of table for this loop */
u8 iSortIdx; /* Sorting index number. 0==None */
LogEst rSetup; /* One-time setup cost (ex: create transient index) */
LogEst rRun; /* Cost of running each loop */
LogEst nOut; /* Estimated number of output rows */
union {
struct { /* Information for internal btree tables */
int nEq; /* Number of equality constraints */
Index *pIndex; /* Index used, or NULL */
} btree;
struct { /* Information for virtual tables */
int idxNum; /* Index number */
u8 needFree; /* True if sqlite3_free(idxStr) is needed */
u8 isOrdered; /* True if satisfies ORDER BY */
u16 omitMask; /* Terms that may be omitted */
char *idxStr; /* Index identifier string */
} vtab;
} u;
u32 wsFlags; /* WHERE_* flags describing the plan */
u16 nLTerm; /* Number of entries in aLTerm[] */
/**** whereLoopXfer() copies fields above ***********************/
# define WHERE_LOOP_XFER_SZ offsetof(WhereLoop,nLSlot)
u16 nLSlot; /* Number of slots allocated for aLTerm[] */
WhereTerm **aLTerm; /* WhereTerms used */
WhereLoop *pNextLoop; /* Next WhereLoop object in the WhereClause */
WhereTerm *aLTermSpace[4]; /* Initial aLTerm[] space */
};
/* This object holds the prerequisites and the cost of running a
** subquery on one operand of an OR operator in the WHERE clause.
** See WhereOrSet for additional information
*/
struct WhereOrCost {
Bitmask prereq; /* Prerequisites */
LogEst rRun; /* Cost of running this subquery */
LogEst nOut; /* Number of outputs for this subquery */
};
/* The WhereOrSet object holds a set of possible WhereOrCosts that
** correspond to the subquery(s) of OR-clause processing. Only the
** best N_OR_COST elements are retained.
*/
#define N_OR_COST 3
struct WhereOrSet {
u16 n; /* Number of valid a[] entries */
WhereOrCost a[N_OR_COST]; /* Set of best costs */
};
/* Forward declaration of methods */
static int whereLoopResize(sqlite3*, WhereLoop*, int);
/*
** Each instance of this object holds a sequence of WhereLoop objects
** that implement some or all of a query plan.
**
** Think of each WhereLoop object as a node in a graph with arcs
** showing dependencies and costs for travelling between nodes. (That is
** not a completely accurate description because WhereLoop costs are a
** vector, not a scalar, and because dependencies are many-to-one, not
** one-to-one as are graph nodes. But it is a useful visualization aid.)
** Then a WherePath object is a path through the graph that visits some
** or all of the WhereLoop objects once.
**
** The "solver" works by creating the N best WherePath objects of length
** 1. Then using those as a basis to compute the N best WherePath objects
** of length 2. And so forth until the length of WherePaths equals the
** number of nodes in the FROM clause. The best (lowest cost) WherePath
** at the end is the choosen query plan.
*/
struct WherePath {
Bitmask maskLoop; /* Bitmask of all WhereLoop objects in this path */
Bitmask revLoop; /* aLoop[]s that should be reversed for ORDER BY */
LogEst nRow; /* Estimated number of rows generated by this path */
LogEst rCost; /* Total cost of this path */
u8 isOrdered; /* True if this path satisfies ORDER BY */
u8 isOrderedValid; /* True if the isOrdered field is valid */
WhereLoop **aLoop; /* Array of WhereLoop objects implementing this path */
};
/*
** The query generator uses an array of instances of this structure to
** help it analyze the subexpressions of the WHERE clause. Each WHERE
** clause subexpression is separated from the others by AND operators,
** usually, or sometimes subexpressions separated by OR.
**
** All WhereTerms are collected into a single WhereClause structure.
** The following identity holds:
**
** WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
**
** When a term is of the form:
**
** X <op> <expr>
**
** where X is a column name and <op> is one of certain operators,
** then WhereTerm.leftCursor and WhereTerm.u.leftColumn record the
** cursor number and column number for X. WhereTerm.eOperator records
** the <op> using a bitmask encoding defined by WO_xxx below. The
** use of a bitmask encoding for the operator allows us to search
** quickly for terms that match any of several different operators.
**
** A WhereTerm might also be two or more subterms connected by OR:
**
** (t1.X <op> <expr>) OR (t1.Y <op> <expr>) OR ....
**
** In this second case, wtFlag has the TERM_ORINFO bit set and eOperator==WO_OR
** and the WhereTerm.u.pOrInfo field points to auxiliary information that
** is collected about the OR clause.
**
** If a term in the WHERE clause does not match either of the two previous
** categories, then eOperator==0. The WhereTerm.pExpr field is still set
** to the original subexpression content and wtFlags is set up appropriately
** but no other fields in the WhereTerm object are meaningful.
**
** When eOperator!=0, prereqRight and prereqAll record sets of cursor numbers,
** but they do so indirectly. A single WhereMaskSet structure translates
** cursor number into bits and the translated bit is stored in the prereq
** fields. The translation is used in order to maximize the number of
** bits that will fit in a Bitmask. The VDBE cursor numbers might be
** spread out over the non-negative integers. For example, the cursor
** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45. The WhereMaskSet
** translates these sparse cursor numbers into consecutive integers
** beginning with 0 in order to make the best possible use of the available
** bits in the Bitmask. So, in the example above, the cursor numbers
** would be mapped into integers 0 through 7.
**
** The number of terms in a join is limited by the number of bits
** in prereqRight and prereqAll. The default is 64 bits, hence SQLite
** is only able to process joins with 64 or fewer tables.
*/
struct WhereTerm {
Expr *pExpr; /* Pointer to the subexpression that is this term */
int iParent; /* Disable pWC->a[iParent] when this term disabled */
int leftCursor; /* Cursor number of X in "X <op> <expr>" */
union {
int leftColumn; /* Column number of X in "X <op> <expr>" */
WhereOrInfo *pOrInfo; /* Extra information if (eOperator & WO_OR)!=0 */
WhereAndInfo *pAndInfo; /* Extra information if (eOperator& WO_AND)!=0 */
} u;
LogEst truthProb; /* Probability of truth for this expression */
u16 eOperator; /* A WO_xx value describing <op> */
u8 wtFlags; /* TERM_xxx bit flags. See below */
u8 nChild; /* Number of children that must disable us */
WhereClause *pWC; /* The clause this term is part of */
Bitmask prereqRight; /* Bitmask of tables used by pExpr->pRight */
Bitmask prereqAll; /* Bitmask of tables referenced by pExpr */
};
/*
** Allowed values of WhereTerm.wtFlags
*/
#define TERM_DYNAMIC 0x01 /* Need to call sqlite3ExprDelete(db, pExpr) */
#define TERM_VIRTUAL 0x02 /* Added by the optimizer. Do not code */
#define TERM_CODED 0x04 /* This term is already coded */
#define TERM_COPIED 0x08 /* Has a child */
#define TERM_ORINFO 0x10 /* Need to free the WhereTerm.u.pOrInfo object */
#define TERM_ANDINFO 0x20 /* Need to free the WhereTerm.u.pAndInfo obj */
#define TERM_OR_OK 0x40 /* Used during OR-clause processing */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
# define TERM_VNULL 0x80 /* Manufactured x>NULL or x<=NULL term */
#else
# define TERM_VNULL 0x00 /* Disabled if not using stat3 */
#endif
/*
** An instance of the WhereScan object is used as an iterator for locating
** terms in the WHERE clause that are useful to the query planner.
*/
struct WhereScan {
WhereClause *pOrigWC; /* Original, innermost WhereClause */
WhereClause *pWC; /* WhereClause currently being scanned */
char *zCollName; /* Required collating sequence, if not NULL */
char idxaff; /* Must match this affinity, if zCollName!=NULL */
unsigned char nEquiv; /* Number of entries in aEquiv[] */
unsigned char iEquiv; /* Next unused slot in aEquiv[] */
u32 opMask; /* Acceptable operators */
int k; /* Resume scanning at this->pWC->a[this->k] */
int aEquiv[22]; /* Cursor,Column pairs for equivalence classes */
};
/*
** An instance of the following structure holds all information about a
** WHERE clause. Mostly this is a container for one or more WhereTerms.
**
** Explanation of pOuter: For a WHERE clause of the form
**
** a AND ((b AND c) OR (d AND e)) AND f
**
** There are separate WhereClause objects for the whole clause and for
** the subclauses "(b AND c)" and "(d AND e)". The pOuter field of the
** subclauses points to the WhereClause object for the whole clause.
*/
struct WhereClause {
WhereInfo *pWInfo; /* WHERE clause processing context */
WhereClause *pOuter; /* Outer conjunction */
u8 op; /* Split operator. TK_AND or TK_OR */
int nTerm; /* Number of terms */
int nSlot; /* Number of entries in a[] */
WhereTerm *a; /* Each a[] describes a term of the WHERE cluase */
#if defined(SQLITE_SMALL_STACK)
WhereTerm aStatic[1]; /* Initial static space for a[] */
#else
WhereTerm aStatic[8]; /* Initial static space for a[] */
#endif
};
/*
** A WhereTerm with eOperator==WO_OR has its u.pOrInfo pointer set to
** a dynamically allocated instance of the following structure.
*/
struct WhereOrInfo {
WhereClause wc; /* Decomposition into subterms */
Bitmask indexable; /* Bitmask of all indexable tables in the clause */
};
/*
** A WhereTerm with eOperator==WO_AND has its u.pAndInfo pointer set to
** a dynamically allocated instance of the following structure.
*/
struct WhereAndInfo {
WhereClause wc; /* The subexpression broken out */
};
/*
** An instance of the following structure keeps track of a mapping
** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
**
** The VDBE cursor numbers are small integers contained in
** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE
** clause, the cursor numbers might not begin with 0 and they might
** contain gaps in the numbering sequence. But we want to make maximum
** use of the bits in our bitmasks. This structure provides a mapping
** from the sparse cursor numbers into consecutive integers beginning
** with 0.
**
** If WhereMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<<A.
**
** For example, if the WHERE clause expression used these VDBE
** cursors: 4, 5, 8, 29, 57, 73. Then the WhereMaskSet structure
** would map those cursor numbers into bits 0 through 5.
**
** Note that the mapping is not necessarily ordered. In the example
** above, the mapping might go like this: 4->3, 5->1, 8->2, 29->0,
** 57->5, 73->4. Or one of 719 other combinations might be used. It
** does not really matter. What is important is that sparse cursor
** numbers all get mapped into bit numbers that begin with 0 and contain
** no gaps.
*/
struct WhereMaskSet {
int n; /* Number of assigned cursor values */
int ix[BMS]; /* Cursor assigned to each bit */
};
/*
** This object is a convenience wrapper holding all information needed
** to construct WhereLoop objects for a particular query.
*/
struct WhereLoopBuilder {
WhereInfo *pWInfo; /* Information about this WHERE */
WhereClause *pWC; /* WHERE clause terms */
ExprList *pOrderBy; /* ORDER BY clause */
WhereLoop *pNew; /* Template WhereLoop */
WhereOrSet *pOrSet; /* Record best loops here, if not NULL */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
UnpackedRecord *pRec; /* Probe for stat4 (if required) */
int nRecValid; /* Number of valid fields currently in pRec */
#endif
};
/*
** The WHERE clause processing routine has two halves. The
** first part does the start of the WHERE loop and the second
** half does the tail of the WHERE loop. An instance of
** this structure is returned by the first half and passed
** into the second half to give some continuity.
**
** An instance of this object holds the complete state of the query
** planner.
*/
struct WhereInfo {
Parse *pParse; /* Parsing and code generating context */
SrcList *pTabList; /* List of tables in the join */
ExprList *pOrderBy; /* The ORDER BY clause or NULL */
ExprList *pResultSet; /* Result set. DISTINCT operates on these */
WhereLoop *pLoops; /* List of all WhereLoop objects */
Bitmask revMask; /* Mask of ORDER BY terms that need reversing */
LogEst nRowOut; /* Estimated number of output rows */
u16 wctrlFlags; /* Flags originally passed to sqlite3WhereBegin() */
u8 bOBSat; /* ORDER BY satisfied by indices */
u8 okOnePass; /* Ok to use one-pass algorithm for UPDATE/DELETE */
u8 untestedTerms; /* Not all WHERE terms resolved by outer loop */
u8 eDistinct; /* One of the WHERE_DISTINCT_* values below */
u8 nLevel; /* Number of nested loop */
int iTop; /* The very beginning of the WHERE loop */
int iContinue; /* Jump here to continue with next record */
int iBreak; /* Jump here to break out of the loop */
int savedNQueryLoop; /* pParse->nQueryLoop outside the WHERE loop */
WhereMaskSet sMaskSet; /* Map cursor numbers to bitmasks */
WhereClause sWC; /* Decomposition of the WHERE clause */
WhereLevel a[1]; /* Information about each nest loop in WHERE */
};
/*
** Bitmasks for the operators on WhereTerm objects. These are all
** operators that are of interest to the query planner. An
** OR-ed combination of these values can be used when searching for
** particular WhereTerms within a WhereClause.
*/
#define WO_IN 0x001
#define WO_EQ 0x002
#define WO_LT (WO_EQ<<(TK_LT-TK_EQ))
#define WO_LE (WO_EQ<<(TK_LE-TK_EQ))
#define WO_GT (WO_EQ<<(TK_GT-TK_EQ))
#define WO_GE (WO_EQ<<(TK_GE-TK_EQ))
#define WO_MATCH 0x040
#define WO_ISNULL 0x080
#define WO_OR 0x100 /* Two or more OR-connected terms */
#define WO_AND 0x200 /* Two or more AND-connected terms */
#define WO_EQUIV 0x400 /* Of the form A==B, both columns */
#define WO_NOOP 0x800 /* This term does not restrict search space */
#define WO_ALL 0xfff /* Mask of all possible WO_* values */
#define WO_SINGLE 0x0ff /* Mask of all non-compound WO_* values */
/*
** These are definitions of bits in the WhereLoop.wsFlags field.
** The particular combination of bits in each WhereLoop help to
** determine the algorithm that WhereLoop represents.
*/
#define WHERE_COLUMN_EQ 0x00000001 /* x=EXPR */
#define WHERE_COLUMN_RANGE 0x00000002 /* x<EXPR and/or x>EXPR */
#define WHERE_COLUMN_IN 0x00000004 /* x IN (...) */
#define WHERE_COLUMN_NULL 0x00000008 /* x IS NULL */
#define WHERE_CONSTRAINT 0x0000000f /* Any of the WHERE_COLUMN_xxx values */
#define WHERE_TOP_LIMIT 0x00000010 /* x<EXPR or x<=EXPR constraint */
#define WHERE_BTM_LIMIT 0x00000020 /* x>EXPR or x>=EXPR constraint */
#define WHERE_BOTH_LIMIT 0x00000030 /* Both x>EXPR and x<EXPR */
#define WHERE_IDX_ONLY 0x00000040 /* Use index only - omit table */
#define WHERE_IPK 0x00000100 /* x is the INTEGER PRIMARY KEY */
#define WHERE_INDEXED 0x00000200 /* WhereLoop.u.btree.pIndex is valid */
#define WHERE_VIRTUALTABLE 0x00000400 /* WhereLoop.u.vtab is valid */
#define WHERE_IN_ABLE 0x00000800 /* Able to support an IN operator */
#define WHERE_ONEROW 0x00001000 /* Selects no more than one row */
#define WHERE_MULTI_OR 0x00002000 /* OR using multiple indices */
#define WHERE_AUTO_INDEX 0x00004000 /* Uses an ephemeral index */
/*
** Return the estimated number of output rows from a WHERE clause
*/
u64 sqlite3WhereOutputRowCount(WhereInfo *pWInfo){
return sqlite3LogEstToInt(pWInfo->nRowOut);
}
/*
** Return one of the WHERE_DISTINCT_xxxxx values to indicate how this
** WHERE clause returns outputs for DISTINCT processing.
*/
int sqlite3WhereIsDistinct(WhereInfo *pWInfo){
return pWInfo->eDistinct;
}
/*
** Return TRUE if the WHERE clause returns rows in ORDER BY order.
** Return FALSE if the output needs to be sorted.
*/
int sqlite3WhereIsOrdered(WhereInfo *pWInfo){
return pWInfo->bOBSat!=0;
}
/*
** Return the VDBE address or label to jump to in order to continue
** immediately with the next row of a WHERE clause.
*/
int sqlite3WhereContinueLabel(WhereInfo *pWInfo){
return pWInfo->iContinue;
}
/*
** Return the VDBE address or label to jump to in order to break
** out of a WHERE loop.
*/
int sqlite3WhereBreakLabel(WhereInfo *pWInfo){
return pWInfo->iBreak;
}
/*
** Return TRUE if an UPDATE or DELETE statement can operate directly on
** the rowids returned by a WHERE clause. Return FALSE if doing an
** UPDATE or DELETE might change subsequent WHERE clause results.
*/
int sqlite3WhereOkOnePass(WhereInfo *pWInfo){
return pWInfo->okOnePass;
}
/*
** Move the content of pSrc into pDest
*/
static void whereOrMove(WhereOrSet *pDest, WhereOrSet *pSrc){
pDest->n = pSrc->n;
memcpy(pDest->a, pSrc->a, pDest->n*sizeof(pDest->a[0]));
}
/*
** Try to insert a new prerequisite/cost entry into the WhereOrSet pSet.
**
** The new entry might overwrite an existing entry, or it might be
** appended, or it might be discarded. Do whatever is the right thing
** so that pSet keeps the N_OR_COST best entries seen so far.
*/
static int whereOrInsert(
WhereOrSet *pSet, /* The WhereOrSet to be updated */
Bitmask prereq, /* Prerequisites of the new entry */
LogEst rRun, /* Run-cost of the new entry */
LogEst nOut /* Number of outputs for the new entry */
){
u16 i;
WhereOrCost *p;
for(i=pSet->n, p=pSet->a; i>0; i--, p++){
if( rRun<=p->rRun && (prereq & p->prereq)==prereq ){
goto whereOrInsert_done;
}
if( p->rRun<=rRun && (p->prereq & prereq)==p->prereq ){
return 0;
}
}
if( pSet->n<N_OR_COST ){
p = &pSet->a[pSet->n++];
p->nOut = nOut;
}else{
p = pSet->a;
for(i=1; i<pSet->n; i++){
if( p->rRun>pSet->a[i].rRun ) p = pSet->a + i;
}
if( p->rRun<=rRun ) return 0;
}
whereOrInsert_done:
p->prereq = prereq;
p->rRun = rRun;
if( p->nOut>nOut ) p->nOut = nOut;
return 1;
}
/*
** Initialize a preallocated WhereClause structure.
*/
static void whereClauseInit(
WhereClause *pWC, /* The WhereClause to be initialized */
WhereInfo *pWInfo /* The WHERE processing context */
){
pWC->pWInfo = pWInfo;
pWC->pOuter = 0;
pWC->nTerm = 0;
pWC->nSlot = ArraySize(pWC->aStatic);
pWC->a = pWC->aStatic;
}
/* Forward reference */
static void whereClauseClear(WhereClause*);
/*
** Deallocate all memory associated with a WhereOrInfo object.
*/
static void whereOrInfoDelete(sqlite3 *db, WhereOrInfo *p){
whereClauseClear(&p->wc);
sqlite3DbFree(db, p);
}
/*
** Deallocate all memory associated with a WhereAndInfo object.
*/
static void whereAndInfoDelete(sqlite3 *db, WhereAndInfo *p){
whereClauseClear(&p->wc);
sqlite3DbFree(db, p);
}
/*
** Deallocate a WhereClause structure. The WhereClause structure
** itself is not freed. This routine is the inverse of whereClauseInit().
*/
static void whereClauseClear(WhereClause *pWC){
int i;
WhereTerm *a;
sqlite3 *db = pWC->pWInfo->pParse->db;
for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
if( a->wtFlags & TERM_DYNAMIC ){
sqlite3ExprDelete(db, a->pExpr);
}
if( a->wtFlags & TERM_ORINFO ){
whereOrInfoDelete(db, a->u.pOrInfo);
}else if( a->wtFlags & TERM_ANDINFO ){
whereAndInfoDelete(db, a->u.pAndInfo);
}
}
if( pWC->a!=pWC->aStatic ){
sqlite3DbFree(db, pWC->a);
}
}
/*
** Add a single new WhereTerm entry to the WhereClause object pWC.
** The new WhereTerm object is constructed from Expr p and with wtFlags.
** The index in pWC->a[] of the new WhereTerm is returned on success.
** 0 is returned if the new WhereTerm could not be added due to a memory
** allocation error. The memory allocation failure will be recorded in
** the db->mallocFailed flag so that higher-level functions can detect it.
**
** This routine will increase the size of the pWC->a[] array as necessary.
**
** If the wtFlags argument includes TERM_DYNAMIC, then responsibility
** for freeing the expression p is assumed by the WhereClause object pWC.
** This is true even if this routine fails to allocate a new WhereTerm.
**
** WARNING: This routine might reallocate the space used to store
** WhereTerms. All pointers to WhereTerms should be invalidated after
** calling this routine. Such pointers may be reinitialized by referencing
** the pWC->a[] array.
*/
static int whereClauseInsert(WhereClause *pWC, Expr *p, u8 wtFlags){
WhereTerm *pTerm;
int idx;
testcase( wtFlags & TERM_VIRTUAL );
if( pWC->nTerm>=pWC->nSlot ){
WhereTerm *pOld = pWC->a;
sqlite3 *db = pWC->pWInfo->pParse->db;
pWC->a = sqlite3DbMallocRaw(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
if( pWC->a==0 ){
if( wtFlags & TERM_DYNAMIC ){
sqlite3ExprDelete(db, p);
}
pWC->a = pOld;
return 0;
}
memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
if( pOld!=pWC->aStatic ){
sqlite3DbFree(db, pOld);
}
pWC->nSlot = sqlite3DbMallocSize(db, pWC->a)/sizeof(pWC->a[0]);
}
pTerm = &pWC->a[idx = pWC->nTerm++];
if( p && ExprHasProperty(p, EP_Unlikely) ){
pTerm->truthProb = sqlite3LogEst(p->iTable) - 99;
}else{
pTerm->truthProb = -1;
}
pTerm->pExpr = sqlite3ExprSkipCollate(p);
pTerm->wtFlags = wtFlags;
pTerm->pWC = pWC;
pTerm->iParent = -1;
return idx;
}
/*
** This routine identifies subexpressions in the WHERE clause where
** each subexpression is separated by the AND operator or some other
** operator specified in the op parameter. The WhereClause structure
** is filled with pointers to subexpressions. For example:
**
** WHERE a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
** \________/ \_______________/ \________________/
** slot[0] slot[1] slot[2]
**
** The original WHERE clause in pExpr is unaltered. All this routine
** does is make slot[] entries point to substructure within pExpr.
**
** In the previous sentence and in the diagram, "slot[]" refers to
** the WhereClause.a[] array. The slot[] array grows as needed to contain
** all terms of the WHERE clause.
*/
static void whereSplit(WhereClause *pWC, Expr *pExpr, u8 op){
pWC->op = op;
if( pExpr==0 ) return;
if( pExpr->op!=op ){
whereClauseInsert(pWC, pExpr, 0);
}else{
whereSplit(pWC, pExpr->pLeft, op);
whereSplit(pWC, pExpr->pRight, op);
}
}
/*
** Initialize a WhereMaskSet object
*/
#define initMaskSet(P) (P)->n=0
/*
** Return the bitmask for the given cursor number. Return 0 if
** iCursor is not in the set.
*/
static Bitmask getMask(WhereMaskSet *pMaskSet, int iCursor){
int i;
assert( pMaskSet->n<=(int)sizeof(Bitmask)*8 );
for(i=0; i<pMaskSet->n; i++){
if( pMaskSet->ix[i]==iCursor ){
return MASKBIT(i);
}
}
return 0;
}
/*
** Create a new mask for cursor iCursor.
**
** There is one cursor per table in the FROM clause. The number of
** tables in the FROM clause is limited by a test early in the
** sqlite3WhereBegin() routine. So we know that the pMaskSet->ix[]
** array will never overflow.
*/
static void createMask(WhereMaskSet *pMaskSet, int iCursor){
assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
pMaskSet->ix[pMaskSet->n++] = iCursor;
}
/*
** These routines walk (recursively) an expression tree and generate
** a bitmask indicating which tables are used in that expression
** tree.
*/
static Bitmask exprListTableUsage(WhereMaskSet*, ExprList*);
static Bitmask exprSelectTableUsage(WhereMaskSet*, Select*);
static Bitmask exprTableUsage(WhereMaskSet *pMaskSet, Expr *p){
Bitmask mask = 0;
if( p==0 ) return 0;
if( p->op==TK_COLUMN ){
mask = getMask(pMaskSet, p->iTable);
return mask;
}
mask = exprTableUsage(pMaskSet, p->pRight);
mask |= exprTableUsage(pMaskSet, p->pLeft);
if( ExprHasProperty(p, EP_xIsSelect) ){
mask |= exprSelectTableUsage(pMaskSet, p->x.pSelect);
}else{
mask |= exprListTableUsage(pMaskSet, p->x.pList);
}
return mask;
}
static Bitmask exprListTableUsage(WhereMaskSet *pMaskSet, ExprList *pList){
int i;
Bitmask mask = 0;
if( pList ){
for(i=0; i<pList->nExpr; i++){
mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
}
}
return mask;
}
static Bitmask exprSelectTableUsage(WhereMaskSet *pMaskSet, Select *pS){
Bitmask mask = 0;
while( pS ){
SrcList *pSrc = pS->pSrc;
mask |= exprListTableUsage(pMaskSet, pS->pEList);
mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
mask |= exprTableUsage(pMaskSet, pS->pWhere);
mask |= exprTableUsage(pMaskSet, pS->pHaving);
if( ALWAYS(pSrc!=0) ){
int i;
for(i=0; i<pSrc->nSrc; i++){
mask |= exprSelectTableUsage(pMaskSet, pSrc->a[i].pSelect);
mask |= exprTableUsage(pMaskSet, pSrc->a[i].pOn);
}
}
pS = pS->pPrior;
}
return mask;
}
/*
** Return TRUE if the given operator is one of the operators that is
** allowed for an indexable WHERE clause term. The allowed operators are
** "=", "<", ">", "<=", ">=", "IN", and "IS NULL"
*/
static int allowedOp(int op){
assert( TK_GT>TK_EQ && TK_GT<TK_GE );
assert( TK_LT>TK_EQ && TK_LT<TK_GE );
assert( TK_LE>TK_EQ && TK_LE<TK_GE );
assert( TK_GE==TK_EQ+4 );
return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL;
}
/*
** Swap two objects of type TYPE.
*/
#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
/*
** Commute a comparison operator. Expressions of the form "X op Y"
** are converted into "Y op X".
**
** If left/right precedence rules come into play when determining the
** collating sequence, then COLLATE operators are adjusted to ensure
** that the collating sequence does not change. For example:
** "Y collate NOCASE op X" becomes "X op Y" because any collation sequence on
** the left hand side of a comparison overrides any collation sequence
** attached to the right. For the same reason the EP_Collate flag
** is not commuted.
*/
static void exprCommute(Parse *pParse, Expr *pExpr){
u16 expRight = (pExpr->pRight->flags & EP_Collate);
u16 expLeft = (pExpr->pLeft->flags & EP_Collate);
assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
if( expRight==expLeft ){
/* Either X and Y both have COLLATE operator or neither do */
if( expRight ){
/* Both X and Y have COLLATE operators. Make sure X is always
** used by clearing the EP_Collate flag from Y. */
pExpr->pRight->flags &= ~EP_Collate;
}else if( sqlite3ExprCollSeq(pParse, pExpr->pLeft)!=0 ){
/* Neither X nor Y have COLLATE operators, but X has a non-default
** collating sequence. So add the EP_Collate marker on X to cause
** it to be searched first. */
pExpr->pLeft->flags |= EP_Collate;
}
}
SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
if( pExpr->op>=TK_GT ){
assert( TK_LT==TK_GT+2 );
assert( TK_GE==TK_LE+2 );
assert( TK_GT>TK_EQ );
assert( TK_GT<TK_LE );
assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
}
}
/*
** Translate from TK_xx operator to WO_xx bitmask.
*/
static u16 operatorMask(int op){
u16 c;
assert( allowedOp(op) );
if( op==TK_IN ){
c = WO_IN;
}else if( op==TK_ISNULL ){
c = WO_ISNULL;
}else{
assert( (WO_EQ<<(op-TK_EQ)) < 0x7fff );
c = (u16)(WO_EQ<<(op-TK_EQ));
}
assert( op!=TK_ISNULL || c==WO_ISNULL );
assert( op!=TK_IN || c==WO_IN );
assert( op!=TK_EQ || c==WO_EQ );
assert( op!=TK_LT || c==WO_LT );
assert( op!=TK_LE || c==WO_LE );
assert( op!=TK_GT || c==WO_GT );
assert( op!=TK_GE || c==WO_GE );
return c;
}
/*
** Advance to the next WhereTerm that matches according to the criteria
** established when the pScan object was initialized by whereScanInit().
** Return NULL if there are no more matching WhereTerms.
*/
static WhereTerm *whereScanNext(WhereScan *pScan){
int iCur; /* The cursor on the LHS of the term */
int iColumn; /* The column on the LHS of the term. -1 for IPK */
Expr *pX; /* An expression being tested */
WhereClause *pWC; /* Shorthand for pScan->pWC */
WhereTerm *pTerm; /* The term being tested */
int k = pScan->k; /* Where to start scanning */
while( pScan->iEquiv<=pScan->nEquiv ){
iCur = pScan->aEquiv[pScan->iEquiv-2];
iColumn = pScan->aEquiv[pScan->iEquiv-1];
while( (pWC = pScan->pWC)!=0 ){
for(pTerm=pWC->a+k; k<pWC->nTerm; k++, pTerm++){
if( pTerm->leftCursor==iCur && pTerm->u.leftColumn==iColumn ){
if( (pTerm->eOperator & WO_EQUIV)!=0
&& pScan->nEquiv<ArraySize(pScan->aEquiv)
){
int j;
pX = sqlite3ExprSkipCollate(pTerm->pExpr->pRight);
assert( pX->op==TK_COLUMN );
for(j=0; j<pScan->nEquiv; j+=2){
if( pScan->aEquiv[j]==pX->iTable
&& pScan->aEquiv[j+1]==pX->iColumn ){
break;
}
}
if( j==pScan->nEquiv ){
pScan->aEquiv[j] = pX->iTable;
pScan->aEquiv[j+1] = pX->iColumn;
pScan->nEquiv += 2;
}
}
if( (pTerm->eOperator & pScan->opMask)!=0 ){
/* Verify the affinity and collating sequence match */
if( pScan->zCollName && (pTerm->eOperator & WO_ISNULL)==0 ){
CollSeq *pColl;
Parse *pParse = pWC->pWInfo->pParse;
pX = pTerm->pExpr;
if( !sqlite3IndexAffinityOk(pX, pScan->idxaff) ){
continue;
}
assert(pX->pLeft);
pColl = sqlite3BinaryCompareCollSeq(pParse,
pX->pLeft, pX->pRight);
if( pColl==0 ) pColl = pParse->db->pDfltColl;
if( sqlite3StrICmp(pColl->zName, pScan->zCollName) ){
continue;
}
}
if( (pTerm->eOperator & WO_EQ)!=0
&& (pX = pTerm->pExpr->pRight)->op==TK_COLUMN
&& pX->iTable==pScan->aEquiv[0]
&& pX->iColumn==pScan->aEquiv[1]
){
continue;
}
pScan->k = k+1;
return pTerm;
}
}
}
pScan->pWC = pScan->pWC->pOuter;
k = 0;
}
pScan->pWC = pScan->pOrigWC;
k = 0;
pScan->iEquiv += 2;
}
return 0;
}
/*
** Initialize a WHERE clause scanner object. Return a pointer to the
** first match. Return NULL if there are no matches.
**
** The scanner will be searching the WHERE clause pWC. It will look
** for terms of the form "X <op> <expr>" where X is column iColumn of table
** iCur. The <op> must be one of the operators described by opMask.
**
** If the search is for X and the WHERE clause contains terms of the
** form X=Y then this routine might also return terms of the form
** "Y <op> <expr>". The number of levels of transitivity is limited,
** but is enough to handle most commonly occurring SQL statements.
**
** If X is not the INTEGER PRIMARY KEY then X must be compatible with
** index pIdx.
*/
static WhereTerm *whereScanInit(
WhereScan *pScan, /* The WhereScan object being initialized */
WhereClause *pWC, /* The WHERE clause to be scanned */
int iCur, /* Cursor to scan for */
int iColumn, /* Column to scan for */
u32 opMask, /* Operator(s) to scan for */
Index *pIdx /* Must be compatible with this index */
){
int j;
/* memset(pScan, 0, sizeof(*pScan)); */
pScan->pOrigWC = pWC;
pScan->pWC = pWC;
if( pIdx && iColumn>=0 ){
pScan->idxaff = pIdx->pTable->aCol[iColumn].affinity;
for(j=0; pIdx->aiColumn[j]!=iColumn; j++){
if( NEVER(j>=pIdx->nColumn) ) return 0;
}
pScan->zCollName = pIdx->azColl[j];
}else{
pScan->idxaff = 0;
pScan->zCollName = 0;
}
pScan->opMask = opMask;
pScan->k = 0;
pScan->aEquiv[0] = iCur;
pScan->aEquiv[1] = iColumn;
pScan->nEquiv = 2;
pScan->iEquiv = 2;
return whereScanNext(pScan);
}
/*
** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
** where X is a reference to the iColumn of table iCur and <op> is one of
** the WO_xx operator codes specified by the op parameter.
** Return a pointer to the term. Return 0 if not found.
**
** The term returned might by Y=<expr> if there is another constraint in
** the WHERE clause that specifies that X=Y. Any such constraints will be
** identified by the WO_EQUIV bit in the pTerm->eOperator field. The
** aEquiv[] array holds X and all its equivalents, with each SQL variable
** taking up two slots in aEquiv[]. The first slot is for the cursor number
** and the second is for the column number. There are 22 slots in aEquiv[]
** so that means we can look for X plus up to 10 other equivalent values.
** Hence a search for X will return <expr> if X=A1 and A1=A2 and A2=A3
** and ... and A9=A10 and A10=<expr>.
**
** If there are multiple terms in the WHERE clause of the form "X <op> <expr>"
** then try for the one with no dependencies on <expr> - in other words where
** <expr> is a constant expression of some kind. Only return entries of
** the form "X <op> Y" where Y is a column in another table if no terms of
** the form "X <op> <const-expr>" exist. If no terms with a constant RHS
** exist, try to return a term that does not use WO_EQUIV.
*/
static WhereTerm *findTerm(
WhereClause *pWC, /* The WHERE clause to be searched */
int iCur, /* Cursor number of LHS */
int iColumn, /* Column number of LHS */
Bitmask notReady, /* RHS must not overlap with this mask */
u32 op, /* Mask of WO_xx values describing operator */
Index *pIdx /* Must be compatible with this index, if not NULL */
){
WhereTerm *pResult = 0;
WhereTerm *p;
WhereScan scan;
p = whereScanInit(&scan, pWC, iCur, iColumn, op, pIdx);
while( p ){
if( (p->prereqRight & notReady)==0 ){
if( p->prereqRight==0 && (p->eOperator&WO_EQ)!=0 ){
return p;
}
if( pResult==0 ) pResult = p;
}
p = whereScanNext(&scan);
}
return pResult;
}
/* Forward reference */
static void exprAnalyze(SrcList*, WhereClause*, int);
/*
** Call exprAnalyze on all terms in a WHERE clause.
*/
static void exprAnalyzeAll(
SrcList *pTabList, /* the FROM clause */
WhereClause *pWC /* the WHERE clause to be analyzed */
){
int i;
for(i=pWC->nTerm-1; i>=0; i--){
exprAnalyze(pTabList, pWC, i);
}
}
#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
/*
** Check to see if the given expression is a LIKE or GLOB operator that
** can be optimized using inequality constraints. Return TRUE if it is
** so and false if not.
**
** In order for the operator to be optimizible, the RHS must be a string
** literal that does not begin with a wildcard.
*/
static int isLikeOrGlob(
Parse *pParse, /* Parsing and code generating context */
Expr *pExpr, /* Test this expression */
Expr **ppPrefix, /* Pointer to TK_STRING expression with pattern prefix */
int *pisComplete, /* True if the only wildcard is % in the last character */
int *pnoCase /* True if uppercase is equivalent to lowercase */
){
const char *z = 0; /* String on RHS of LIKE operator */
Expr *pRight, *pLeft; /* Right and left size of LIKE operator */
ExprList *pList; /* List of operands to the LIKE operator */
int c; /* One character in z[] */
int cnt; /* Number of non-wildcard prefix characters */
char wc[3]; /* Wildcard characters */
sqlite3 *db = pParse->db; /* Database connection */
sqlite3_value *pVal = 0;
int op; /* Opcode of pRight */
if( !sqlite3IsLikeFunction(db, pExpr, pnoCase, wc) ){
return 0;
}
#ifdef SQLITE_EBCDIC
if( *pnoCase ) return 0;
#endif
pList = pExpr->x.pList;
pLeft = pList->a[1].pExpr;
if( pLeft->op!=TK_COLUMN
|| sqlite3ExprAffinity(pLeft)!=SQLITE_AFF_TEXT
|| IsVirtual(pLeft->pTab)
){
/* IMP: R-02065-49465 The left-hand side of the LIKE or GLOB operator must
** be the name of an indexed column with TEXT affinity. */
return 0;
}
assert( pLeft->iColumn!=(-1) ); /* Because IPK never has AFF_TEXT */
pRight = pList->a[0].pExpr;
op = pRight->op;
if( op==TK_REGISTER ){
op = pRight->op2;
}
if( op==TK_VARIABLE ){
Vdbe *pReprepare = pParse->pReprepare;
int iCol = pRight->iColumn;
pVal = sqlite3VdbeGetBoundValue(pReprepare, iCol, SQLITE_AFF_NONE);
if( pVal && sqlite3_value_type(pVal)==SQLITE_TEXT ){
z = (char *)sqlite3_value_text(pVal);
}
sqlite3VdbeSetVarmask(pParse->pVdbe, iCol);
assert( pRight->op==TK_VARIABLE || pRight->op==TK_REGISTER );
}else if( op==TK_STRING ){
z = pRight->u.zToken;
}
if( z ){
cnt = 0;
while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){
cnt++;
}
if( cnt!=0 && 255!=(u8)z[cnt-1] ){
Expr *pPrefix;
*pisComplete = c==wc[0] && z[cnt+1]==0;
pPrefix = sqlite3Expr(db, TK_STRING, z);
if( pPrefix ) pPrefix->u.zToken[cnt] = 0;
*ppPrefix = pPrefix;
if( op==TK_VARIABLE ){
Vdbe *v = pParse->pVdbe;
sqlite3VdbeSetVarmask(v, pRight->iColumn);
if( *pisComplete && pRight->u.zToken[1] ){
/* If the rhs of the LIKE expression is a variable, and the current
** value of the variable means there is no need to invoke the LIKE
** function, then no OP_Variable will be added to the program.
** This causes problems for the sqlite3_bind_parameter_name()
** API. To workaround them, add a dummy OP_Variable here.
*/
int r1 = sqlite3GetTempReg(pParse);
sqlite3ExprCodeTarget(pParse, pRight, r1);
sqlite3VdbeChangeP3(v, sqlite3VdbeCurrentAddr(v)-1, 0);
sqlite3ReleaseTempReg(pParse, r1);
}
}
}else{
z = 0;
}
}
sqlite3ValueFree(pVal);
return (z!=0);
}
#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
#ifndef SQLITE_OMIT_VIRTUALTABLE
/*
** Check to see if the given expression is of the form
**
** column MATCH expr
**
** If it is then return TRUE. If not, return FALSE.
*/
static int isMatchOfColumn(
Expr *pExpr /* Test this expression */
){
ExprList *pList;
if( pExpr->op!=TK_FUNCTION ){
return 0;
}
if( sqlite3StrICmp(pExpr->u.zToken,"match")!=0 ){
return 0;
}
pList = pExpr->x.pList;
if( pList->nExpr!=2 ){
return 0;
}
if( pList->a[1].pExpr->op != TK_COLUMN ){
return 0;
}
return 1;
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */
/*
** If the pBase expression originated in the ON or USING clause of
** a join, then transfer the appropriate markings over to derived.
*/
static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
if( pDerived ){
pDerived->flags |= pBase->flags & EP_FromJoin;
pDerived->iRightJoinTable = pBase->iRightJoinTable;
}
}
#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
/*
** Analyze a term that consists of two or more OR-connected
** subterms. So in:
**
** ... WHERE (a=5) AND (b=7 OR c=9 OR d=13) AND (d=13)
** ^^^^^^^^^^^^^^^^^^^^
**
** This routine analyzes terms such as the middle term in the above example.
** A WhereOrTerm object is computed and attached to the term under
** analysis, regardless of the outcome of the analysis. Hence:
**
** WhereTerm.wtFlags |= TERM_ORINFO
** WhereTerm.u.pOrInfo = a dynamically allocated WhereOrTerm object
**
** The term being analyzed must have two or more of OR-connected subterms.
** A single subterm might be a set of AND-connected sub-subterms.
** Examples of terms under analysis:
**
** (A) t1.x=t2.y OR t1.x=t2.z OR t1.y=15 OR t1.z=t3.a+5
** (B) x=expr1 OR expr2=x OR x=expr3
** (C) t1.x=t2.y OR (t1.x=t2.z AND t1.y=15)
** (D) x=expr1 OR (y>11 AND y<22 AND z LIKE '*hello*')
** (E) (p.a=1 AND q.b=2 AND r.c=3) OR (p.x=4 AND q.y=5 AND r.z=6)
**
** CASE 1:
**
** If all subterms are of the form T.C=expr for some single column of C and
** a single table T (as shown in example B above) then create a new virtual
** term that is an equivalent IN expression. In other words, if the term
** being analyzed is:
**
** x = expr1 OR expr2 = x OR x = expr3
**
** then create a new virtual term like this:
**
** x IN (expr1,expr2,expr3)
**
** CASE 2:
**
** If all subterms are indexable by a single table T, then set
**
** WhereTerm.eOperator = WO_OR
** WhereTerm.u.pOrInfo->indexable |= the cursor number for table T
**
** A subterm is "indexable" if it is of the form
** "T.C <op> <expr>" where C is any column of table T and
** <op> is one of "=", "<", "<=", ">", ">=", "IS NULL", or "IN".
** A subterm is also indexable if it is an AND of two or more
** subsubterms at least one of which is indexable. Indexable AND
** subterms have their eOperator set to WO_AND and they have
** u.pAndInfo set to a dynamically allocated WhereAndTerm object.
**
** From another point of view, "indexable" means that the subterm could
** potentially be used with an index if an appropriate index exists.
** This analysis does not consider whether or not the index exists; that
** is decided elsewhere. This analysis only looks at whether subterms
** appropriate for indexing exist.
**
** All examples A through E above satisfy case 2. But if a term
** also statisfies case 1 (such as B) we know that the optimizer will
** always prefer case 1, so in that case we pretend that case 2 is not
** satisfied.
**
** It might be the case that multiple tables are indexable. For example,
** (E) above is indexable on tables P, Q, and R.
**
** Terms that satisfy case 2 are candidates for lookup by using
** separate indices to find rowids for each subterm and composing
** the union of all rowids using a RowSet object. This is similar
** to "bitmap indices" in other database engines.
**
** OTHERWISE:
**
** If neither case 1 nor case 2 apply, then leave the eOperator set to
** zero. This term is not useful for search.
*/
static void exprAnalyzeOrTerm(
SrcList *pSrc, /* the FROM clause */
WhereClause *pWC, /* the complete WHERE clause */
int idxTerm /* Index of the OR-term to be analyzed */
){
WhereInfo *pWInfo = pWC->pWInfo; /* WHERE clause processing context */
Parse *pParse = pWInfo->pParse; /* Parser context */
sqlite3 *db = pParse->db; /* Database connection */
WhereTerm *pTerm = &pWC->a[idxTerm]; /* The term to be analyzed */
Expr *pExpr = pTerm->pExpr; /* The expression of the term */
int i; /* Loop counters */
WhereClause *pOrWc; /* Breakup of pTerm into subterms */
WhereTerm *pOrTerm; /* A Sub-term within the pOrWc */
WhereOrInfo *pOrInfo; /* Additional information associated with pTerm */
Bitmask chngToIN; /* Tables that might satisfy case 1 */
Bitmask indexable; /* Tables that are indexable, satisfying case 2 */
/*
** Break the OR clause into its separate subterms. The subterms are
** stored in a WhereClause structure containing within the WhereOrInfo
** object that is attached to the original OR clause term.
*/
assert( (pTerm->wtFlags & (TERM_DYNAMIC|TERM_ORINFO|TERM_ANDINFO))==0 );
assert( pExpr->op==TK_OR );
pTerm->u.pOrInfo = pOrInfo = sqlite3DbMallocZero(db, sizeof(*pOrInfo));
if( pOrInfo==0 ) return;
pTerm->wtFlags |= TERM_ORINFO;
pOrWc = &pOrInfo->wc;
whereClauseInit(pOrWc, pWInfo);
whereSplit(pOrWc, pExpr, TK_OR);
exprAnalyzeAll(pSrc, pOrWc);
if( db->mallocFailed ) return;
assert( pOrWc->nTerm>=2 );
/*
** Compute the set of tables that might satisfy cases 1 or 2.
*/
indexable = ~(Bitmask)0;
chngToIN = ~(Bitmask)0;
for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0 && indexable; i--, pOrTerm++){
if( (pOrTerm->eOperator & WO_SINGLE)==0 ){
WhereAndInfo *pAndInfo;
assert( (pOrTerm->wtFlags & (TERM_ANDINFO|TERM_ORINFO))==0 );
chngToIN = 0;
pAndInfo = sqlite3DbMallocRaw(db, sizeof(*pAndInfo));
if( pAndInfo ){
WhereClause *pAndWC;
WhereTerm *pAndTerm;
int j;
Bitmask b = 0;
pOrTerm->u.pAndInfo = pAndInfo;
pOrTerm->wtFlags |= TERM_ANDINFO;
pOrTerm->eOperator = WO_AND;
pAndWC = &pAndInfo->wc;
whereClauseInit(pAndWC, pWC->pWInfo);
whereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
exprAnalyzeAll(pSrc, pAndWC);
pAndWC->pOuter = pWC;
testcase( db->mallocFailed );
if( !db->mallocFailed ){
for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
assert( pAndTerm->pExpr );
if( allowedOp(pAndTerm->pExpr->op) ){
b |= getMask(&pWInfo->sMaskSet, pAndTerm->leftCursor);
}
}
}
indexable &= b;
}
}else if( pOrTerm->wtFlags & TERM_COPIED ){
/* Skip this term for now. We revisit it when we process the
** corresponding TERM_VIRTUAL term */
}else{
Bitmask b;
b = getMask(&pWInfo->sMaskSet, pOrTerm->leftCursor);
if( pOrTerm->wtFlags & TERM_VIRTUAL ){
WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
b |= getMask(&pWInfo->sMaskSet, pOther->leftCursor);
}
indexable &= b;
if( (pOrTerm->eOperator & WO_EQ)==0 ){
chngToIN = 0;
}else{
chngToIN &= b;
}
}
}
/*
** Record the set of tables that satisfy case 2. The set might be
** empty.
*/
pOrInfo->indexable = indexable;
pTerm->eOperator = indexable==0 ? 0 : WO_OR;
/*
** chngToIN holds a set of tables that *might* satisfy case 1. But
** we have to do some additional checking to see if case 1 really
** is satisfied.
**
** chngToIN will hold either 0, 1, or 2 bits. The 0-bit case means
** that there is no possibility of transforming the OR clause into an
** IN operator because one or more terms in the OR clause contain
** something other than == on a column in the single table. The 1-bit
** case means that every term of the OR clause is of the form
** "table.column=expr" for some single table. The one bit that is set
** will correspond to the common table. We still need to check to make
** sure the same column is used on all terms. The 2-bit case is when
** the all terms are of the form "table1.column=table2.column". It
** might be possible to form an IN operator with either table1.column
** or table2.column as the LHS if either is common to every term of
** the OR clause.
**
** Note that terms of the form "table.column1=table.column2" (the
** same table on both sizes of the ==) cannot be optimized.
*/
if( chngToIN ){
int okToChngToIN = 0; /* True if the conversion to IN is valid */
int iColumn = -1; /* Column index on lhs of IN operator */
int iCursor = -1; /* Table cursor common to all terms */
int j = 0; /* Loop counter */
/* Search for a table and column that appears on one side or the
** other of the == operator in every subterm. That table and column
** will be recorded in iCursor and iColumn. There might not be any
** such table and column. Set okToChngToIN if an appropriate table
** and column is found but leave okToChngToIN false if not found.
*/
for(j=0; j<2 && !okToChngToIN; j++){
pOrTerm = pOrWc->a;
for(i=pOrWc->nTerm-1; i>=0; i--, pOrTerm++){
assert( pOrTerm->eOperator & WO_EQ );
pOrTerm->wtFlags &= ~TERM_OR_OK;
if( pOrTerm->leftCursor==iCursor ){
/* This is the 2-bit case and we are on the second iteration and
** current term is from the first iteration. So skip this term. */
assert( j==1 );
continue;
}
if( (chngToIN & getMask(&pWInfo->sMaskSet, pOrTerm->leftCursor))==0 ){
/* This term must be of the form t1.a==t2.b where t2 is in the
** chngToIN set but t1 is not. This term will be either preceeded
** or follwed by an inverted copy (t2.b==t1.a). Skip this term
** and use its inversion. */
testcase( pOrTerm->wtFlags & TERM_COPIED );
testcase( pOrTerm->wtFlags & TERM_VIRTUAL );
assert( pOrTerm->wtFlags & (TERM_COPIED|TERM_VIRTUAL) );
continue;
}
iColumn = pOrTerm->u.leftColumn;
iCursor = pOrTerm->leftCursor;
break;
}
if( i<0 ){
/* No candidate table+column was found. This can only occur
** on the second iteration */
assert( j==1 );
assert( IsPowerOfTwo(chngToIN) );
assert( chngToIN==getMask(&pWInfo->sMaskSet, iCursor) );
break;
}
testcase( j==1 );
/* We have found a candidate table and column. Check to see if that
** table and column is common to every term in the OR clause */
okToChngToIN = 1;
for(; i>=0 && okToChngToIN; i--, pOrTerm++){
assert( pOrTerm->eOperator & WO_EQ );
if( pOrTerm->leftCursor!=iCursor ){
pOrTerm->wtFlags &= ~TERM_OR_OK;
}else if( pOrTerm->u.leftColumn!=iColumn ){
okToChngToIN = 0;
}else{
int affLeft, affRight;
/* If the right-hand side is also a column, then the affinities
** of both right and left sides must be such that no type
** conversions are required on the right. (Ticket #2249)
*/
affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
if( affRight!=0 && affRight!=affLeft ){
okToChngToIN = 0;
}else{
pOrTerm->wtFlags |= TERM_OR_OK;
}
}
}
}
/* At this point, okToChngToIN is true if original pTerm satisfies
** case 1. In that case, construct a new virtual term that is
** pTerm converted into an IN operator.
*/
if( okToChngToIN ){
Expr *pDup; /* A transient duplicate expression */
ExprList *pList = 0; /* The RHS of the IN operator */
Expr *pLeft = 0; /* The LHS of the IN operator */
Expr *pNew; /* The complete IN operator */
for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0; i--, pOrTerm++){
if( (pOrTerm->wtFlags & TERM_OR_OK)==0 ) continue;
assert( pOrTerm->eOperator & WO_EQ );
assert( pOrTerm->leftCursor==iCursor );
assert( pOrTerm->u.leftColumn==iColumn );
pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight, 0);
pList = sqlite3ExprListAppend(pWInfo->pParse, pList, pDup);
pLeft = pOrTerm->pExpr->pLeft;
}
assert( pLeft!=0 );
pDup = sqlite3ExprDup(db, pLeft, 0);
pNew = sqlite3PExpr(pParse, TK_IN, pDup, 0, 0);
if( pNew ){
int idxNew;
transferJoinMarkings(pNew, pExpr);
assert( !ExprHasProperty(pNew, EP_xIsSelect) );
pNew->x.pList = pList;
idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew==0 );
exprAnalyze(pSrc, pWC, idxNew);
pTerm = &pWC->a[idxTerm];
pWC->a[idxNew].iParent = idxTerm;
pTerm->nChild = 1;
}else{
sqlite3ExprListDelete(db, pList);
}
pTerm->eOperator = WO_NOOP; /* case 1 trumps case 2 */
}
}
}
#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
/*
** The input to this routine is an WhereTerm structure with only the
** "pExpr" field filled in. The job of this routine is to analyze the
** subexpression and populate all the other fields of the WhereTerm
** structure.
**
** If the expression is of the form "<expr> <op> X" it gets commuted
** to the standard form of "X <op> <expr>".
**
** If the expression is of the form "X <op> Y" where both X and Y are
** columns, then the original expression is unchanged and a new virtual
** term of the form "Y <op> X" is added to the WHERE clause and
** analyzed separately. The original term is marked with TERM_COPIED
** and the new term is marked with TERM_DYNAMIC (because it's pExpr
** needs to be freed with the WhereClause) and TERM_VIRTUAL (because it
** is a commuted copy of a prior term.) The original term has nChild=1
** and the copy has idxParent set to the index of the original term.
*/
static void exprAnalyze(
SrcList *pSrc, /* the FROM clause */
WhereClause *pWC, /* the WHERE clause */
int idxTerm /* Index of the term to be analyzed */
){
WhereInfo *pWInfo = pWC->pWInfo; /* WHERE clause processing context */
WhereTerm *pTerm; /* The term to be analyzed */
WhereMaskSet *pMaskSet; /* Set of table index masks */
Expr *pExpr; /* The expression to be analyzed */
Bitmask prereqLeft; /* Prerequesites of the pExpr->pLeft */
Bitmask prereqAll; /* Prerequesites of pExpr */
Bitmask extraRight = 0; /* Extra dependencies on LEFT JOIN */
Expr *pStr1 = 0; /* RHS of LIKE/GLOB operator */
int isComplete = 0; /* RHS of LIKE/GLOB ends with wildcard */
int noCase = 0; /* LIKE/GLOB distinguishes case */
int op; /* Top-level operator. pExpr->op */
Parse *pParse = pWInfo->pParse; /* Parsing context */
sqlite3 *db = pParse->db; /* Database connection */
if( db->mallocFailed ){
return;
}
pTerm = &pWC->a[idxTerm];
pMaskSet = &pWInfo->sMaskSet;
pExpr = pTerm->pExpr;
assert( pExpr->op!=TK_AS && pExpr->op!=TK_COLLATE );
prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
op = pExpr->op;
if( op==TK_IN ){
assert( pExpr->pRight==0 );
if( ExprHasProperty(pExpr, EP_xIsSelect) ){
pTerm->prereqRight = exprSelectTableUsage(pMaskSet, pExpr->x.pSelect);
}else{
pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->x.pList);
}
}else if( op==TK_ISNULL ){
pTerm->prereqRight = 0;
}else{
pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
}
prereqAll = exprTableUsage(pMaskSet, pExpr);
if( ExprHasProperty(pExpr, EP_FromJoin) ){
Bitmask x = getMask(pMaskSet, pExpr->iRightJoinTable);
prereqAll |= x;
extraRight = x-1; /* ON clause terms may not be used with an index
** on left table of a LEFT JOIN. Ticket #3015 */
}
pTerm->prereqAll = prereqAll;
pTerm->leftCursor = -1;
pTerm->iParent = -1;
pTerm->eOperator = 0;
if( allowedOp(op) ){
Expr *pLeft = sqlite3ExprSkipCollate(pExpr->pLeft);
Expr *pRight = sqlite3ExprSkipCollate(pExpr->pRight);
u16 opMask = (pTerm->prereqRight & prereqLeft)==0 ? WO_ALL : WO_EQUIV;
if( pLeft->op==TK_COLUMN ){
pTerm->leftCursor = pLeft->iTable;
pTerm->u.leftColumn = pLeft->iColumn;
pTerm->eOperator = operatorMask(op) & opMask;
}
if( pRight && pRight->op==TK_COLUMN ){
WhereTerm *pNew;
Expr *pDup;
u16 eExtraOp = 0; /* Extra bits for pNew->eOperator */
if( pTerm->leftCursor>=0 ){
int idxNew;
pDup = sqlite3ExprDup(db, pExpr, 0);
if( db->mallocFailed ){
sqlite3ExprDelete(db, pDup);
return;
}
idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
if( idxNew==0 ) return;
pNew = &pWC->a[idxNew];
pNew->iParent = idxTerm;
pTerm = &pWC->a[idxTerm];
pTerm->nChild = 1;
pTerm->wtFlags |= TERM_COPIED;
if( pExpr->op==TK_EQ
&& !ExprHasProperty(pExpr, EP_FromJoin)
&& OptimizationEnabled(db, SQLITE_Transitive)
){
pTerm->eOperator |= WO_EQUIV;
eExtraOp = WO_EQUIV;
}
}else{
pDup = pExpr;
pNew = pTerm;
}
exprCommute(pParse, pDup);
pLeft = sqlite3ExprSkipCollate(pDup->pLeft);
pNew->leftCursor = pLeft->iTable;
pNew->u.leftColumn = pLeft->iColumn;
testcase( (prereqLeft | extraRight) != prereqLeft );
pNew->prereqRight = prereqLeft | extraRight;
pNew->prereqAll = prereqAll;
pNew->eOperator = (operatorMask(pDup->op) + eExtraOp) & opMask;
}
}
#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
/* If a term is the BETWEEN operator, create two new virtual terms
** that define the range that the BETWEEN implements. For example:
**
** a BETWEEN b AND c
**
** is converted into:
**
** (a BETWEEN b AND c) AND (a>=b) AND (a<=c)
**
** The two new terms are added onto the end of the WhereClause object.
** The new terms are "dynamic" and are children of the original BETWEEN
** term. That means that if the BETWEEN term is coded, the children are
** skipped. Or, if the children are satisfied by an index, the original
** BETWEEN term is skipped.
*/
else if( pExpr->op==TK_BETWEEN && pWC->op==TK_AND ){
ExprList *pList = pExpr->x.pList;
int i;
static const u8 ops[] = {TK_GE, TK_LE};
assert( pList!=0 );
assert( pList->nExpr==2 );
for(i=0; i<2; i++){
Expr *pNewExpr;
int idxNew;
pNewExpr = sqlite3PExpr(pParse, ops[i],
sqlite3ExprDup(db, pExpr->pLeft, 0),
sqlite3ExprDup(db, pList->a[i].pExpr, 0), 0);
transferJoinMarkings(pNewExpr, pExpr);
idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew==0 );
exprAnalyze(pSrc, pWC, idxNew);
pTerm = &pWC->a[idxTerm];
pWC->a[idxNew].iParent = idxTerm;
}
pTerm->nChild = 2;
}
#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
/* Analyze a term that is composed of two or more subterms connected by
** an OR operator.
*/
else if( pExpr->op==TK_OR ){
assert( pWC->op==TK_AND );
exprAnalyzeOrTerm(pSrc, pWC, idxTerm);
pTerm = &pWC->a[idxTerm];
}
#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
/* Add constraints to reduce the search space on a LIKE or GLOB
** operator.
**
** A like pattern of the form "x LIKE 'abc%'" is changed into constraints
**
** x>='abc' AND x<'abd' AND x LIKE 'abc%'
**
** The last character of the prefix "abc" is incremented to form the
** termination condition "abd".
*/
if( pWC->op==TK_AND
&& isLikeOrGlob(pParse, pExpr, &pStr1, &isComplete, &noCase)
){
Expr *pLeft; /* LHS of LIKE/GLOB operator */
Expr *pStr2; /* Copy of pStr1 - RHS of LIKE/GLOB operator */
Expr *pNewExpr1;
Expr *pNewExpr2;
int idxNew1;
int idxNew2;
Token sCollSeqName; /* Name of collating sequence */
pLeft = pExpr->x.pList->a[1].pExpr;
pStr2 = sqlite3ExprDup(db, pStr1, 0);
if( !db->mallocFailed ){
u8 c, *pC; /* Last character before the first wildcard */
pC = (u8*)&pStr2->u.zToken[sqlite3Strlen30(pStr2->u.zToken)-1];
c = *pC;
if( noCase ){
/* The point is to increment the last character before the first
** wildcard. But if we increment '@', that will push it into the
** alphabetic range where case conversions will mess up the
** inequality. To avoid this, make sure to also run the full
** LIKE on all candidate expressions by clearing the isComplete flag
*/
if( c=='A'-1 ) isComplete = 0;
c = sqlite3UpperToLower[c];
}
*pC = c + 1;
}
sCollSeqName.z = noCase ? "NOCASE" : "BINARY";
sCollSeqName.n = 6;
pNewExpr1 = sqlite3ExprDup(db, pLeft, 0);
pNewExpr1 = sqlite3PExpr(pParse, TK_GE,
sqlite3ExprAddCollateToken(pParse,pNewExpr1,&sCollSeqName),
pStr1, 0);
transferJoinMarkings(pNewExpr1, pExpr);
idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew1==0 );
exprAnalyze(pSrc, pWC, idxNew1);
pNewExpr2 = sqlite3ExprDup(db, pLeft, 0);
pNewExpr2 = sqlite3PExpr(pParse, TK_LT,
sqlite3ExprAddCollateToken(pParse,pNewExpr2,&sCollSeqName),
pStr2, 0);
transferJoinMarkings(pNewExpr2, pExpr);
idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew2==0 );
exprAnalyze(pSrc, pWC, idxNew2);
pTerm = &pWC->a[idxTerm];
if( isComplete ){
pWC->a[idxNew1].iParent = idxTerm;
pWC->a[idxNew2].iParent = idxTerm;
pTerm->nChild = 2;
}
}
#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Add a WO_MATCH auxiliary term to the constraint set if the
** current expression is of the form: column MATCH expr.
** This information is used by the xBestIndex methods of
** virtual tables. The native query optimizer does not attempt
** to do anything with MATCH functions.
*/
if( isMatchOfColumn(pExpr) ){
int idxNew;
Expr *pRight, *pLeft;
WhereTerm *pNewTerm;
Bitmask prereqColumn, prereqExpr;
pRight = pExpr->x.pList->a[0].pExpr;
pLeft = pExpr->x.pList->a[1].pExpr;
prereqExpr = exprTableUsage(pMaskSet, pRight);
prereqColumn = exprTableUsage(pMaskSet, pLeft);
if( (prereqExpr & prereqColumn)==0 ){
Expr *pNewExpr;
pNewExpr = sqlite3PExpr(pParse, TK_MATCH,
0, sqlite3ExprDup(db, pRight, 0), 0);
idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew==0 );
pNewTerm = &pWC->a[idxNew];
pNewTerm->prereqRight = prereqExpr;
pNewTerm->leftCursor = pLeft->iTable;
pNewTerm->u.leftColumn = pLeft->iColumn;
pNewTerm->eOperator = WO_MATCH;
pNewTerm->iParent = idxTerm;
pTerm = &pWC->a[idxTerm];
pTerm->nChild = 1;
pTerm->wtFlags |= TERM_COPIED;
pNewTerm->prereqAll = pTerm->prereqAll;
}
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
/* When sqlite_stat3 histogram data is available an operator of the
** form "x IS NOT NULL" can sometimes be evaluated more efficiently
** as "x>NULL" if x is not an INTEGER PRIMARY KEY. So construct a
** virtual term of that form.
**
** Note that the virtual term must be tagged with TERM_VNULL. This
** TERM_VNULL tag will suppress the not-null check at the beginning
** of the loop. Without the TERM_VNULL flag, the not-null check at
** the start of the loop will prevent any results from being returned.
*/
if( pExpr->op==TK_NOTNULL
&& pExpr->pLeft->op==TK_COLUMN
&& pExpr->pLeft->iColumn>=0
&& OptimizationEnabled(db, SQLITE_Stat3)
){
Expr *pNewExpr;
Expr *pLeft = pExpr->pLeft;
int idxNew;
WhereTerm *pNewTerm;
pNewExpr = sqlite3PExpr(pParse, TK_GT,
sqlite3ExprDup(db, pLeft, 0),
sqlite3PExpr(pParse, TK_NULL, 0, 0, 0), 0);
idxNew = whereClauseInsert(pWC, pNewExpr,
TERM_VIRTUAL|TERM_DYNAMIC|TERM_VNULL);
if( idxNew ){
pNewTerm = &pWC->a[idxNew];
pNewTerm->prereqRight = 0;
pNewTerm->leftCursor = pLeft->iTable;
pNewTerm->u.leftColumn = pLeft->iColumn;
pNewTerm->eOperator = WO_GT;
pNewTerm->iParent = idxTerm;
pTerm = &pWC->a[idxTerm];
pTerm->nChild = 1;
pTerm->wtFlags |= TERM_COPIED;
pNewTerm->prereqAll = pTerm->prereqAll;
}
}
#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
/* Prevent ON clause terms of a LEFT JOIN from being used to drive
** an index for tables to the left of the join.
*/
pTerm->prereqRight |= extraRight;
}
/*
** This function searches pList for a entry that matches the iCol-th column
** of index pIdx.
**
** If such an expression is found, its index in pList->a[] is returned. If
** no expression is found, -1 is returned.
*/
static int findIndexCol(
Parse *pParse, /* Parse context */
ExprList *pList, /* Expression list to search */
int iBase, /* Cursor for table associated with pIdx */
Index *pIdx, /* Index to match column of */
int iCol /* Column of index to match */
){
int i;
const char *zColl = pIdx->azColl[iCol];
for(i=0; i<pList->nExpr; i++){
Expr *p = sqlite3ExprSkipCollate(pList->a[i].pExpr);
if( p->op==TK_COLUMN
&& p->iColumn==pIdx->aiColumn[iCol]
&& p->iTable==iBase
){
CollSeq *pColl = sqlite3ExprCollSeq(pParse, pList->a[i].pExpr);
if( ALWAYS(pColl) && 0==sqlite3StrICmp(pColl->zName, zColl) ){
return i;
}
}
}
return -1;
}
/*
** Return true if the DISTINCT expression-list passed as the third argument
** is redundant.
**
** A DISTINCT list is redundant if the database contains some subset of
** columns that are unique and non-null.
*/
static int isDistinctRedundant(
Parse *pParse, /* Parsing context */
SrcList *pTabList, /* The FROM clause */
WhereClause *pWC, /* The WHERE clause */
ExprList *pDistinct /* The result set that needs to be DISTINCT */
){
Table *pTab;
Index *pIdx;
int i;
int iBase;
/* If there is more than one table or sub-select in the FROM clause of
** this query, then it will not be possible to show that the DISTINCT
** clause is redundant. */
if( pTabList->nSrc!=1 ) return 0;
iBase = pTabList->a[0].iCursor;
pTab = pTabList->a[0].pTab;
/* If any of the expressions is an IPK column on table iBase, then return
** true. Note: The (p->iTable==iBase) part of this test may be false if the
** current SELECT is a correlated sub-query.
*/
for(i=0; i<pDistinct->nExpr; i++){
Expr *p = sqlite3ExprSkipCollate(pDistinct->a[i].pExpr);
if( p->op==TK_COLUMN && p->iTable==iBase && p->iColumn<0 ) return 1;
}
/* Loop through all indices on the table, checking each to see if it makes
** the DISTINCT qualifier redundant. It does so if:
**
** 1. The index is itself UNIQUE, and
**
** 2. All of the columns in the index are either part of the pDistinct
** list, or else the WHERE clause contains a term of the form "col=X",
** where X is a constant value. The collation sequences of the
** comparison and select-list expressions must match those of the index.
**
** 3. All of those index columns for which the WHERE clause does not
** contain a "col=X" term are subject to a NOT NULL constraint.
*/
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
if( pIdx->onError==OE_None ) continue;
for(i=0; i<pIdx->nColumn; i++){
int iCol = pIdx->aiColumn[i];
if( 0==findTerm(pWC, iBase, iCol, ~(Bitmask)0, WO_EQ, pIdx) ){
int iIdxCol = findIndexCol(pParse, pDistinct, iBase, pIdx, i);
if( iIdxCol<0 || pTab->aCol[pIdx->aiColumn[i]].notNull==0 ){
break;
}
}
}
if( i==pIdx->nColumn ){
/* This index implies that the DISTINCT qualifier is redundant. */
return 1;
}
}
return 0;
}
/*
** Estimate the logarithm of the input value to base 2.
*/
static LogEst estLog(LogEst N){
LogEst x = sqlite3LogEst(N);
return x>33 ? x - 33 : 0;
}
/*
** Two routines for printing the content of an sqlite3_index_info
** structure. Used for testing and debugging only. If neither
** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
** are no-ops.
*/
#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(WHERETRACE_ENABLED)
static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
int i;
if( !sqlite3WhereTrace ) return;
for(i=0; i<p->nConstraint; i++){
sqlite3DebugPrintf(" constraint[%d]: col=%d termid=%d op=%d usabled=%d\n",
i,
p->aConstraint[i].iColumn,
p->aConstraint[i].iTermOffset,
p->aConstraint[i].op,
p->aConstraint[i].usable);
}
for(i=0; i<p->nOrderBy; i++){
sqlite3DebugPrintf(" orderby[%d]: col=%d desc=%d\n",
i,
p->aOrderBy[i].iColumn,
p->aOrderBy[i].desc);
}
}
static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){
int i;
if( !sqlite3WhereTrace ) return;
for(i=0; i<p->nConstraint; i++){
sqlite3DebugPrintf(" usage[%d]: argvIdx=%d omit=%d\n",
i,
p->aConstraintUsage[i].argvIndex,
p->aConstraintUsage[i].omit);
}
sqlite3DebugPrintf(" idxNum=%d\n", p->idxNum);
sqlite3DebugPrintf(" idxStr=%s\n", p->idxStr);
sqlite3DebugPrintf(" orderByConsumed=%d\n", p->orderByConsumed);
sqlite3DebugPrintf(" estimatedCost=%g\n", p->estimatedCost);
}
#else
#define TRACE_IDX_INPUTS(A)
#define TRACE_IDX_OUTPUTS(A)
#endif
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
/*
** Return TRUE if the WHERE clause term pTerm is of a form where it
** could be used with an index to access pSrc, assuming an appropriate
** index existed.
*/
static int termCanDriveIndex(
WhereTerm *pTerm, /* WHERE clause term to check */
struct SrcList_item *pSrc, /* Table we are trying to access */
Bitmask notReady /* Tables in outer loops of the join */
){
char aff;
if( pTerm->leftCursor!=pSrc->iCursor ) return 0;
if( (pTerm->eOperator & WO_EQ)==0 ) return 0;
if( (pTerm->prereqRight & notReady)!=0 ) return 0;
if( pTerm->u.leftColumn<0 ) return 0;
aff = pSrc->pTab->aCol[pTerm->u.leftColumn].affinity;
if( !sqlite3IndexAffinityOk(pTerm->pExpr, aff) ) return 0;
return 1;
}
#endif
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
/*
** Generate code to construct the Index object for an automatic index
** and to set up the WhereLevel object pLevel so that the code generator
** makes use of the automatic index.
*/
static void constructAutomaticIndex(
Parse *pParse, /* The parsing context */
WhereClause *pWC, /* The WHERE clause */
struct SrcList_item *pSrc, /* The FROM clause term to get the next index */
Bitmask notReady, /* Mask of cursors that are not available */
WhereLevel *pLevel /* Write new index here */
){
int nColumn; /* Number of columns in the constructed index */
WhereTerm *pTerm; /* A single term of the WHERE clause */
WhereTerm *pWCEnd; /* End of pWC->a[] */
int nByte; /* Byte of memory needed for pIdx */
Index *pIdx; /* Object describing the transient index */
Vdbe *v; /* Prepared statement under construction */
int addrInit; /* Address of the initialization bypass jump */
Table *pTable; /* The table being indexed */
KeyInfo *pKeyinfo; /* Key information for the index */
int addrTop; /* Top of the index fill loop */
int regRecord; /* Register holding an index record */
int n; /* Column counter */
int i; /* Loop counter */
int mxBitCol; /* Maximum column in pSrc->colUsed */
CollSeq *pColl; /* Collating sequence to on a column */
WhereLoop *pLoop; /* The Loop object */
Bitmask idxCols; /* Bitmap of columns used for indexing */
Bitmask extraCols; /* Bitmap of additional columns */
u8 sentWarning = 0; /* True if a warnning has been issued */
/* Generate code to skip over the creation and initialization of the
** transient index on 2nd and subsequent iterations of the loop. */
v = pParse->pVdbe;
assert( v!=0 );
addrInit = sqlite3CodeOnce(pParse);
/* Count the number of columns that will be added to the index
** and used to match WHERE clause constraints */
nColumn = 0;
pTable = pSrc->pTab;
pWCEnd = &pWC->a[pWC->nTerm];
pLoop = pLevel->pWLoop;
idxCols = 0;
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( termCanDriveIndex(pTerm, pSrc, notReady) ){
int iCol = pTerm->u.leftColumn;
Bitmask cMask = iCol>=BMS ? MASKBIT(BMS-1) : MASKBIT(iCol);
testcase( iCol==BMS );
testcase( iCol==BMS-1 );
if( !sentWarning ){
sqlite3_log(SQLITE_WARNING_AUTOINDEX,
"automatic index on %s(%s)", pTable->zName,
pTable->aCol[iCol].zName);
sentWarning = 1;
}
if( (idxCols & cMask)==0 ){
if( whereLoopResize(pParse->db, pLoop, nColumn+1) ) return;
pLoop->aLTerm[nColumn++] = pTerm;
idxCols |= cMask;
}
}
}
assert( nColumn>0 );
pLoop->u.btree.nEq = pLoop->nLTerm = nColumn;
pLoop->wsFlags = WHERE_COLUMN_EQ | WHERE_IDX_ONLY | WHERE_INDEXED
| WHERE_AUTO_INDEX;
/* Count the number of additional columns needed to create a
** covering index. A "covering index" is an index that contains all
** columns that are needed by the query. With a covering index, the
** original table never needs to be accessed. Automatic indices must
** be a covering index because the index will not be updated if the
** original table changes and the index and table cannot both be used
** if they go out of sync.
*/
extraCols = pSrc->colUsed & (~idxCols | MASKBIT(BMS-1));
mxBitCol = (pTable->nCol >= BMS-1) ? BMS-1 : pTable->nCol;
testcase( pTable->nCol==BMS-1 );
testcase( pTable->nCol==BMS-2 );
for(i=0; i<mxBitCol; i++){
if( extraCols & MASKBIT(i) ) nColumn++;
}
if( pSrc->colUsed & MASKBIT(BMS-1) ){
nColumn += pTable->nCol - BMS + 1;
}
pLoop->wsFlags |= WHERE_COLUMN_EQ | WHERE_IDX_ONLY;
/* Construct the Index object to describe this index */
nByte = sizeof(Index);
nByte += nColumn*sizeof(int); /* Index.aiColumn */
nByte += nColumn*sizeof(char*); /* Index.azColl */
nByte += nColumn; /* Index.aSortOrder */
pIdx = sqlite3DbMallocZero(pParse->db, nByte);
if( pIdx==0 ) return;
pLoop->u.btree.pIndex = pIdx;
pIdx->azColl = (char**)&pIdx[1];
pIdx->aiColumn = (int*)&pIdx->azColl[nColumn];
pIdx->aSortOrder = (u8*)&pIdx->aiColumn[nColumn];
pIdx->zName = "auto-index";
pIdx->nColumn = nColumn;
pIdx->pTable = pTable;
n = 0;
idxCols = 0;
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( termCanDriveIndex(pTerm, pSrc, notReady) ){
int iCol = pTerm->u.leftColumn;
Bitmask cMask = iCol>=BMS ? MASKBIT(BMS-1) : MASKBIT(iCol);
testcase( iCol==BMS-1 );
testcase( iCol==BMS );
if( (idxCols & cMask)==0 ){
Expr *pX = pTerm->pExpr;
idxCols |= cMask;
pIdx->aiColumn[n] = pTerm->u.leftColumn;
pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
pIdx->azColl[n] = ALWAYS(pColl) ? pColl->zName : "BINARY";
n++;
}
}
}
assert( (u32)n==pLoop->u.btree.nEq );
/* Add additional columns needed to make the automatic index into
** a covering index */
for(i=0; i<mxBitCol; i++){
if( extraCols & MASKBIT(i) ){
pIdx->aiColumn[n] = i;
pIdx->azColl[n] = "BINARY";
n++;
}
}
if( pSrc->colUsed & MASKBIT(BMS-1) ){
for(i=BMS-1; i<pTable->nCol; i++){
pIdx->aiColumn[n] = i;
pIdx->azColl[n] = "BINARY";
n++;
}
}
assert( n==nColumn );
/* Create the automatic index */
pKeyinfo = sqlite3IndexKeyinfo(pParse, pIdx);
assert( pLevel->iIdxCur>=0 );
pLevel->iIdxCur = pParse->nTab++;
sqlite3VdbeAddOp4(v, OP_OpenAutoindex, pLevel->iIdxCur, nColumn+1, 0,
(char*)pKeyinfo, P4_KEYINFO_HANDOFF);
VdbeComment((v, "for %s", pTable->zName));
/* Fill the automatic index with content */
addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur);
regRecord = sqlite3GetTempReg(pParse);
sqlite3GenerateIndexKey(pParse, pIdx, pLevel->iTabCur, regRecord, 1, 0);
sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1);
sqlite3VdbeChangeP5(v, SQLITE_STMTSTATUS_AUTOINDEX);
sqlite3VdbeJumpHere(v, addrTop);
sqlite3ReleaseTempReg(pParse, regRecord);
/* Jump here when skipping the initialization */
sqlite3VdbeJumpHere(v, addrInit);
}
#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
#ifndef SQLITE_OMIT_VIRTUALTABLE
/*
** Allocate and populate an sqlite3_index_info structure. It is the
** responsibility of the caller to eventually release the structure
** by passing the pointer returned by this function to sqlite3_free().
*/
static sqlite3_index_info *allocateIndexInfo(
Parse *pParse,
WhereClause *pWC,
struct SrcList_item *pSrc,
ExprList *pOrderBy
){
int i, j;
int nTerm;
struct sqlite3_index_constraint *pIdxCons;
struct sqlite3_index_orderby *pIdxOrderBy;
struct sqlite3_index_constraint_usage *pUsage;
WhereTerm *pTerm;
int nOrderBy;
sqlite3_index_info *pIdxInfo;
/* Count the number of possible WHERE clause constraints referring
** to this virtual table */
for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
if( pTerm->leftCursor != pSrc->iCursor ) continue;
assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
testcase( pTerm->eOperator & WO_IN );
testcase( pTerm->eOperator & WO_ISNULL );
if( pTerm->eOperator & (WO_ISNULL) ) continue;
if( pTerm->wtFlags & TERM_VNULL ) continue;
nTerm++;
}
/* If the ORDER BY clause contains only columns in the current
** virtual table then allocate space for the aOrderBy part of
** the sqlite3_index_info structure.
*/
nOrderBy = 0;
if( pOrderBy ){
int n = pOrderBy->nExpr;
for(i=0; i<n; i++){
Expr *pExpr = pOrderBy->a[i].pExpr;
if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
}
if( i==n){
nOrderBy = n;
}
}
/* Allocate the sqlite3_index_info structure
*/
pIdxInfo = sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
+ (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
+ sizeof(*pIdxOrderBy)*nOrderBy );
if( pIdxInfo==0 ){
sqlite3ErrorMsg(pParse, "out of memory");
return 0;
}
/* Initialize the structure. The sqlite3_index_info structure contains
** many fields that are declared "const" to prevent xBestIndex from
** changing them. We have to do some funky casting in order to
** initialize those fields.
*/
pIdxCons = (struct sqlite3_index_constraint*)&pIdxInfo[1];
pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
*(int*)&pIdxInfo->nConstraint = nTerm;
*(int*)&pIdxInfo->nOrderBy = nOrderBy;
*(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
*(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
*(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
pUsage;
for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
u8 op;
if( pTerm->leftCursor != pSrc->iCursor ) continue;
assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
testcase( pTerm->eOperator & WO_IN );
testcase( pTerm->eOperator & WO_ISNULL );
if( pTerm->eOperator & (WO_ISNULL) ) continue;
if( pTerm->wtFlags & TERM_VNULL ) continue;
pIdxCons[j].iColumn = pTerm->u.leftColumn;
pIdxCons[j].iTermOffset = i;
op = (u8)pTerm->eOperator & WO_ALL;
if( op==WO_IN ) op = WO_EQ;
pIdxCons[j].op = op;
/* The direct assignment in the previous line is possible only because
** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical. The
** following asserts verify this fact. */
assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
assert( pTerm->eOperator & (WO_IN|WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
j++;
}
for(i=0; i<nOrderBy; i++){
Expr *pExpr = pOrderBy->a[i].pExpr;
pIdxOrderBy[i].iColumn = pExpr->iColumn;
pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
}
return pIdxInfo;
}
/*
** The table object reference passed as the second argument to this function
** must represent a virtual table. This function invokes the xBestIndex()
** method of the virtual table with the sqlite3_index_info object that
** comes in as the 3rd argument to this function.
**
** If an error occurs, pParse is populated with an error message and a
** non-zero value is returned. Otherwise, 0 is returned and the output
** part of the sqlite3_index_info structure is left populated.
**
** Whether or not an error is returned, it is the responsibility of the
** caller to eventually free p->idxStr if p->needToFreeIdxStr indicates
** that this is required.
*/
static int vtabBestIndex(Parse *pParse, Table *pTab, sqlite3_index_info *p){
sqlite3_vtab *pVtab = sqlite3GetVTable(pParse->db, pTab)->pVtab;
int i;
int rc;
TRACE_IDX_INPUTS(p);
rc = pVtab->pModule->xBestIndex(pVtab, p);
TRACE_IDX_OUTPUTS(p);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_NOMEM ){
pParse->db->mallocFailed = 1;
}else if( !pVtab->zErrMsg ){
sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
}else{
sqlite3ErrorMsg(pParse, "%s", pVtab->zErrMsg);
}
}
sqlite3_free(pVtab->zErrMsg);
pVtab->zErrMsg = 0;
for(i=0; i<p->nConstraint; i++){
if( !p->aConstraint[i].usable && p->aConstraintUsage[i].argvIndex>0 ){
sqlite3ErrorMsg(pParse,
"table %s: xBestIndex returned an invalid plan", pTab->zName);
}
}
return pParse->nErr;
}
#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
/*
** Estimate the location of a particular key among all keys in an
** index. Store the results in aStat as follows:
**
** aStat[0] Est. number of rows less than pVal
** aStat[1] Est. number of rows equal to pVal
**
** Return SQLITE_OK on success.
*/
static void whereKeyStats(
Parse *pParse, /* Database connection */
Index *pIdx, /* Index to consider domain of */
UnpackedRecord *pRec, /* Vector of values to consider */
int roundUp, /* Round up if true. Round down if false */
tRowcnt *aStat /* OUT: stats written here */
){
IndexSample *aSample = pIdx->aSample;
int iCol; /* Index of required stats in anEq[] etc. */
int iMin = 0; /* Smallest sample not yet tested */
int i = pIdx->nSample; /* Smallest sample larger than or equal to pRec */
int iTest; /* Next sample to test */
int res; /* Result of comparison operation */
#ifndef SQLITE_DEBUG
UNUSED_PARAMETER( pParse );
#endif
assert( pRec!=0 || pParse->db->mallocFailed );
if( pRec==0 ) return;
iCol = pRec->nField - 1;
assert( pIdx->nSample>0 );
assert( pRec->nField>0 && iCol<pIdx->nSampleCol );
do{
iTest = (iMin+i)/2;
res = sqlite3VdbeRecordCompare(aSample[iTest].n, aSample[iTest].p, pRec);
if( res<0 ){
iMin = iTest+1;
}else{
i = iTest;
}
}while( res && iMin<i );
#ifdef SQLITE_DEBUG
/* The following assert statements check that the binary search code
** above found the right answer. This block serves no purpose other
** than to invoke the asserts. */
if( res==0 ){
/* If (res==0) is true, then sample $i must be equal to pRec */
assert( i<pIdx->nSample );
assert( 0==sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)
|| pParse->db->mallocFailed );
}else{
/* Otherwise, pRec must be smaller than sample $i and larger than
** sample ($i-1). */
assert( i==pIdx->nSample
|| sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)>0
|| pParse->db->mallocFailed );
assert( i==0
|| sqlite3VdbeRecordCompare(aSample[i-1].n, aSample[i-1].p, pRec)<0
|| pParse->db->mallocFailed );
}
#endif /* ifdef SQLITE_DEBUG */
/* At this point, aSample[i] is the first sample that is greater than
** or equal to pVal. Or if i==pIdx->nSample, then all samples are less
** than pVal. If aSample[i]==pVal, then res==0.
*/
if( res==0 ){
aStat[0] = aSample[i].anLt[iCol];
aStat[1] = aSample[i].anEq[iCol];
}else{
tRowcnt iLower, iUpper, iGap;
if( i==0 ){
iLower = 0;
iUpper = aSample[0].anLt[iCol];
}else{
iUpper = i>=pIdx->nSample ? pIdx->aiRowEst[0] : aSample[i].anLt[iCol];
iLower = aSample[i-1].anEq[iCol] + aSample[i-1].anLt[iCol];
}
aStat[1] = (pIdx->nColumn>iCol ? pIdx->aAvgEq[iCol] : 1);
if( iLower>=iUpper ){
iGap = 0;
}else{
iGap = iUpper - iLower;
}
if( roundUp ){
iGap = (iGap*2)/3;
}else{
iGap = iGap/3;
}
aStat[0] = iLower + iGap;
}
}
#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
/*
** This function is used to estimate the number of rows that will be visited
** by scanning an index for a range of values. The range may have an upper
** bound, a lower bound, or both. The WHERE clause terms that set the upper
** and lower bounds are represented by pLower and pUpper respectively. For
** example, assuming that index p is on t1(a):
**
** ... FROM t1 WHERE a > ? AND a < ? ...
** |_____| |_____|
** | |
** pLower pUpper
**
** If either of the upper or lower bound is not present, then NULL is passed in
** place of the corresponding WhereTerm.
**
** The value in (pBuilder->pNew->u.btree.nEq) is the index of the index
** column subject to the range constraint. Or, equivalently, the number of
** equality constraints optimized by the proposed index scan. For example,
** assuming index p is on t1(a, b), and the SQL query is:
**
** ... FROM t1 WHERE a = ? AND b > ? AND b < ? ...
**
** then nEq is set to 1 (as the range restricted column, b, is the second
** left-most column of the index). Or, if the query is:
**
** ... FROM t1 WHERE a > ? AND a < ? ...
**
** then nEq is set to 0.
**
** When this function is called, *pnOut is set to the sqlite3LogEst() of the
** number of rows that the index scan is expected to visit without
** considering the range constraints. If nEq is 0, this is the number of
** rows in the index. Assuming no error occurs, *pnOut is adjusted (reduced)
** to account for the range contraints pLower and pUpper.
**
** In the absence of sqlite_stat4 ANALYZE data, or if such data cannot be
** used, each range inequality reduces the search space by a factor of 4.
** Hence a pair of constraints (x>? AND x<?) reduces the expected number of
** rows visited by a factor of 16.
*/
static int whereRangeScanEst(
Parse *pParse, /* Parsing & code generating context */
WhereLoopBuilder *pBuilder,
WhereTerm *pLower, /* Lower bound on the range. ex: "x>123" Might be NULL */
WhereTerm *pUpper, /* Upper bound on the range. ex: "x<455" Might be NULL */
WhereLoop *pLoop /* Modify the .nOut and maybe .rRun fields */
){
int rc = SQLITE_OK;
int nOut = pLoop->nOut;
LogEst nNew;
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
Index *p = pLoop->u.btree.pIndex;
int nEq = pLoop->u.btree.nEq;
if( p->nSample>0
&& nEq==pBuilder->nRecValid
&& nEq<p->nSampleCol
&& OptimizationEnabled(pParse->db, SQLITE_Stat3)
){
UnpackedRecord *pRec = pBuilder->pRec;
tRowcnt a[2];
u8 aff;
/* Variable iLower will be set to the estimate of the number of rows in
** the index that are less than the lower bound of the range query. The
** lower bound being the concatenation of $P and $L, where $P is the
** key-prefix formed by the nEq values matched against the nEq left-most
** columns of the index, and $L is the value in pLower.
**
** Or, if pLower is NULL or $L cannot be extracted from it (because it
** is not a simple variable or literal value), the lower bound of the
** range is $P. Due to a quirk in the way whereKeyStats() works, even
** if $L is available, whereKeyStats() is called for both ($P) and
** ($P:$L) and the larger of the two returned values used.
**
** Similarly, iUpper is to be set to the estimate of the number of rows
** less than the upper bound of the range query. Where the upper bound
** is either ($P) or ($P:$U). Again, even if $U is available, both values
** of iUpper are requested of whereKeyStats() and the smaller used.
*/
tRowcnt iLower;
tRowcnt iUpper;
if( nEq==p->nColumn ){
aff = SQLITE_AFF_INTEGER;
}else{
aff = p->pTable->aCol[p->aiColumn[nEq]].affinity;
}
/* Determine iLower and iUpper using ($P) only. */
if( nEq==0 ){
iLower = 0;
iUpper = p->aiRowEst[0];
}else{
/* Note: this call could be optimized away - since the same values must
** have been requested when testing key $P in whereEqualScanEst(). */
whereKeyStats(pParse, p, pRec, 0, a);
iLower = a[0];
iUpper = a[0] + a[1];
}
/* If possible, improve on the iLower estimate using ($P:$L). */
if( pLower ){
int bOk; /* True if value is extracted from pExpr */
Expr *pExpr = pLower->pExpr->pRight;
assert( (pLower->eOperator & (WO_GT|WO_GE))!=0 );
rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq, &bOk);
if( rc==SQLITE_OK && bOk ){
tRowcnt iNew;
whereKeyStats(pParse, p, pRec, 0, a);
iNew = a[0] + ((pLower->eOperator & WO_GT) ? a[1] : 0);
if( iNew>iLower ) iLower = iNew;
nOut--;
}
}
/* If possible, improve on the iUpper estimate using ($P:$U). */
if( pUpper ){
int bOk; /* True if value is extracted from pExpr */
Expr *pExpr = pUpper->pExpr->pRight;
assert( (pUpper->eOperator & (WO_LT|WO_LE))!=0 );
rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq, &bOk);
if( rc==SQLITE_OK && bOk ){
tRowcnt iNew;
whereKeyStats(pParse, p, pRec, 1, a);
iNew = a[0] + ((pUpper->eOperator & WO_LE) ? a[1] : 0);
if( iNew<iUpper ) iUpper = iNew;
nOut--;
}
}
pBuilder->pRec = pRec;
if( rc==SQLITE_OK ){
if( iUpper>iLower ){
nNew = sqlite3LogEst(iUpper - iLower);
}else{
nNew = 10; assert( 10==sqlite3LogEst(2) );
}
if( nNew<nOut ){
nOut = nNew;
}
pLoop->nOut = (LogEst)nOut;
WHERETRACE(0x100, ("range scan regions: %u..%u est=%d\n",
(u32)iLower, (u32)iUpper, nOut));
return SQLITE_OK;
}
}
#else
UNUSED_PARAMETER(pParse);
UNUSED_PARAMETER(pBuilder);
#endif
assert( pLower || pUpper );
/* TUNING: Each inequality constraint reduces the search space 4-fold.
** A BETWEEN operator, therefore, reduces the search space 16-fold */
nNew = nOut;
if( pLower && (pLower->wtFlags & TERM_VNULL)==0 ){
nNew -= 20; assert( 20==sqlite3LogEst(4) );
nOut--;
}
if( pUpper ){
nNew -= 20; assert( 20==sqlite3LogEst(4) );
nOut--;
}
if( nNew<10 ) nNew = 10;
if( nNew<nOut ) nOut = nNew;
pLoop->nOut = (LogEst)nOut;
return rc;
}
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
/*
** Estimate the number of rows that will be returned based on
** an equality constraint x=VALUE and where that VALUE occurs in
** the histogram data. This only works when x is the left-most
** column of an index and sqlite_stat3 histogram data is available
** for that index. When pExpr==NULL that means the constraint is
** "x IS NULL" instead of "x=VALUE".
**
** Write the estimated row count into *pnRow and return SQLITE_OK.
** If unable to make an estimate, leave *pnRow unchanged and return
** non-zero.
**
** This routine can fail if it is unable to load a collating sequence
** required for string comparison, or if unable to allocate memory
** for a UTF conversion required for comparison. The error is stored
** in the pParse structure.
*/
static int whereEqualScanEst(
Parse *pParse, /* Parsing & code generating context */
WhereLoopBuilder *pBuilder,
Expr *pExpr, /* Expression for VALUE in the x=VALUE constraint */
tRowcnt *pnRow /* Write the revised row estimate here */
){
Index *p = pBuilder->pNew->u.btree.pIndex;
int nEq = pBuilder->pNew->u.btree.nEq;
UnpackedRecord *pRec = pBuilder->pRec;
u8 aff; /* Column affinity */
int rc; /* Subfunction return code */
tRowcnt a[2]; /* Statistics */
int bOk;
assert( nEq>=1 );
assert( nEq<=(p->nColumn+1) );
assert( p->aSample!=0 );
assert( p->nSample>0 );
assert( pBuilder->nRecValid<nEq );
/* If values are not available for all fields of the index to the left
** of this one, no estimate can be made. Return SQLITE_NOTFOUND. */
if( pBuilder->nRecValid<(nEq-1) ){
return SQLITE_NOTFOUND;
}
/* This is an optimization only. The call to sqlite3Stat4ProbeSetValue()
** below would return the same value. */
if( nEq>p->nColumn ){
*pnRow = 1;
return SQLITE_OK;
}
aff = p->pTable->aCol[p->aiColumn[nEq-1]].affinity;
rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq-1, &bOk);
pBuilder->pRec = pRec;
if( rc!=SQLITE_OK ) return rc;
if( bOk==0 ) return SQLITE_NOTFOUND;
pBuilder->nRecValid = nEq;
whereKeyStats(pParse, p, pRec, 0, a);
WHERETRACE(0x100,("equality scan regions: %d\n", (int)a[1]));
*pnRow = a[1];
return rc;
}
#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
/*
** Estimate the number of rows that will be returned based on
** an IN constraint where the right-hand side of the IN operator
** is a list of values. Example:
**
** WHERE x IN (1,2,3,4)
**
** Write the estimated row count into *pnRow and return SQLITE_OK.
** If unable to make an estimate, leave *pnRow unchanged and return
** non-zero.
**
** This routine can fail if it is unable to load a collating sequence
** required for string comparison, or if unable to allocate memory
** for a UTF conversion required for comparison. The error is stored
** in the pParse structure.
*/
static int whereInScanEst(
Parse *pParse, /* Parsing & code generating context */
WhereLoopBuilder *pBuilder,
ExprList *pList, /* The value list on the RHS of "x IN (v1,v2,v3,...)" */
tRowcnt *pnRow /* Write the revised row estimate here */
){
Index *p = pBuilder->pNew->u.btree.pIndex;
int nRecValid = pBuilder->nRecValid;
int rc = SQLITE_OK; /* Subfunction return code */
tRowcnt nEst; /* Number of rows for a single term */
tRowcnt nRowEst = 0; /* New estimate of the number of rows */
int i; /* Loop counter */
assert( p->aSample!=0 );
for(i=0; rc==SQLITE_OK && i<pList->nExpr; i++){
nEst = p->aiRowEst[0];
rc = whereEqualScanEst(pParse, pBuilder, pList->a[i].pExpr, &nEst);
nRowEst += nEst;
pBuilder->nRecValid = nRecValid;
}
if( rc==SQLITE_OK ){
if( nRowEst > p->aiRowEst[0] ) nRowEst = p->aiRowEst[0];
*pnRow = nRowEst;
WHERETRACE(0x100,("IN row estimate: est=%g\n", nRowEst));
}
assert( pBuilder->nRecValid==nRecValid );
return rc;
}
#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
/*
** Disable a term in the WHERE clause. Except, do not disable the term
** if it controls a LEFT OUTER JOIN and it did not originate in the ON
** or USING clause of that join.
**
** Consider the term t2.z='ok' in the following queries:
**
** (1) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
** (2) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
**
** The t2.z='ok' is disabled in the in (2) because it originates
** in the ON clause. The term is disabled in (3) because it is not part
** of a LEFT OUTER JOIN. In (1), the term is not disabled.
**
** Disabling a term causes that term to not be tested in the inner loop
** of the join. Disabling is an optimization. When terms are satisfied
** by indices, we disable them to prevent redundant tests in the inner
** loop. We would get the correct results if nothing were ever disabled,
** but joins might run a little slower. The trick is to disable as much
** as we can without disabling too much. If we disabled in (1), we'd get
** the wrong answer. See ticket #813.
*/
static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
if( pTerm
&& (pTerm->wtFlags & TERM_CODED)==0
&& (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
&& (pLevel->notReady & pTerm->prereqAll)==0
){
pTerm->wtFlags |= TERM_CODED;
if( pTerm->iParent>=0 ){
WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
if( (--pOther->nChild)==0 ){
disableTerm(pLevel, pOther);
}
}
}
}
/*
** Code an OP_Affinity opcode to apply the column affinity string zAff
** to the n registers starting at base.
**
** As an optimization, SQLITE_AFF_NONE entries (which are no-ops) at the
** beginning and end of zAff are ignored. If all entries in zAff are
** SQLITE_AFF_NONE, then no code gets generated.
**
** This routine makes its own copy of zAff so that the caller is free
** to modify zAff after this routine returns.
*/
static void codeApplyAffinity(Parse *pParse, int base, int n, char *zAff){
Vdbe *v = pParse->pVdbe;
if( zAff==0 ){
assert( pParse->db->mallocFailed );
return;
}
assert( v!=0 );
/* Adjust base and n to skip over SQLITE_AFF_NONE entries at the beginning
** and end of the affinity string.
*/
while( n>0 && zAff[0]==SQLITE_AFF_NONE ){
n--;
base++;
zAff++;
}
while( n>1 && zAff[n-1]==SQLITE_AFF_NONE ){
n--;
}
/* Code the OP_Affinity opcode if there is anything left to do. */
if( n>0 ){
sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
sqlite3VdbeChangeP4(v, -1, zAff, n);
sqlite3ExprCacheAffinityChange(pParse, base, n);
}
}
/*
** Generate code for a single equality term of the WHERE clause. An equality
** term can be either X=expr or X IN (...). pTerm is the term to be
** coded.
**
** The current value for the constraint is left in register iReg.
**
** For a constraint of the form X=expr, the expression is evaluated and its
** result is left on the stack. For constraints of the form X IN (...)
** this routine sets up a loop that will iterate over all values of X.
*/
static int codeEqualityTerm(
Parse *pParse, /* The parsing context */
WhereTerm *pTerm, /* The term of the WHERE clause to be coded */
WhereLevel *pLevel, /* The level of the FROM clause we are working on */
int iEq, /* Index of the equality term within this level */
int bRev, /* True for reverse-order IN operations */
int iTarget /* Attempt to leave results in this register */
){
Expr *pX = pTerm->pExpr;
Vdbe *v = pParse->pVdbe;
int iReg; /* Register holding results */
assert( iTarget>0 );
if( pX->op==TK_EQ ){
iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
}else if( pX->op==TK_ISNULL ){
iReg = iTarget;
sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
#ifndef SQLITE_OMIT_SUBQUERY
}else{
int eType;
int iTab;
struct InLoop *pIn;
WhereLoop *pLoop = pLevel->pWLoop;
if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0
&& pLoop->u.btree.pIndex!=0
&& pLoop->u.btree.pIndex->aSortOrder[iEq]
){
testcase( iEq==0 );
testcase( bRev );
bRev = !bRev;
}
assert( pX->op==TK_IN );
iReg = iTarget;
eType = sqlite3FindInIndex(pParse, pX, 0);
if( eType==IN_INDEX_INDEX_DESC ){
testcase( bRev );
bRev = !bRev;
}
iTab = pX->iTable;
sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iTab, 0);
assert( (pLoop->wsFlags & WHERE_MULTI_OR)==0 );
pLoop->wsFlags |= WHERE_IN_ABLE;
if( pLevel->u.in.nIn==0 ){
pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
}
pLevel->u.in.nIn++;
pLevel->u.in.aInLoop =
sqlite3DbReallocOrFree(pParse->db, pLevel->u.in.aInLoop,
sizeof(pLevel->u.in.aInLoop[0])*pLevel->u.in.nIn);
pIn = pLevel->u.in.aInLoop;
if( pIn ){
pIn += pLevel->u.in.nIn - 1;
pIn->iCur = iTab;
if( eType==IN_INDEX_ROWID ){
pIn->addrInTop = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iReg);
}else{
pIn->addrInTop = sqlite3VdbeAddOp3(v, OP_Column, iTab, 0, iReg);
}
pIn->eEndLoopOp = bRev ? OP_Prev : OP_Next;
sqlite3VdbeAddOp1(v, OP_IsNull, iReg);
}else{
pLevel->u.in.nIn = 0;
}
#endif
}
disableTerm(pLevel, pTerm);
return iReg;
}
/*
** Generate code that will evaluate all == and IN constraints for an
** index.
**
** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
** Suppose the WHERE clause is this: a==5 AND b IN (1,2,3) AND c>5 AND c<10
** The index has as many as three equality constraints, but in this
** example, the third "c" value is an inequality. So only two
** constraints are coded. This routine will generate code to evaluate
** a==5 and b IN (1,2,3). The current values for a and b will be stored
** in consecutive registers and the index of the first register is returned.
**
** In the example above nEq==2. But this subroutine works for any value
** of nEq including 0. If nEq==0, this routine is nearly a no-op.
** The only thing it does is allocate the pLevel->iMem memory cell and
** compute the affinity string.
**
** This routine always allocates at least one memory cell and returns
** the index of that memory cell. The code that
** calls this routine will use that memory cell to store the termination
** key value of the loop. If one or more IN operators appear, then
** this routine allocates an additional nEq memory cells for internal
** use.
**
** Before returning, *pzAff is set to point to a buffer containing a
** copy of the column affinity string of the index allocated using
** sqlite3DbMalloc(). Except, entries in the copy of the string associated
** with equality constraints that use NONE affinity are set to
** SQLITE_AFF_NONE. This is to deal with SQL such as the following:
**
** CREATE TABLE t1(a TEXT PRIMARY KEY, b);
** SELECT ... FROM t1 AS t2, t1 WHERE t1.a = t2.b;
**
** In the example above, the index on t1(a) has TEXT affinity. But since
** the right hand side of the equality constraint (t2.b) has NONE affinity,
** no conversion should be attempted before using a t2.b value as part of
** a key to search the index. Hence the first byte in the returned affinity
** string in this example would be set to SQLITE_AFF_NONE.
*/
static int codeAllEqualityTerms(
Parse *pParse, /* Parsing context */
WhereLevel *pLevel, /* Which nested loop of the FROM we are coding */
int bRev, /* Reverse the order of IN operators */
int nExtraReg, /* Number of extra registers to allocate */
char **pzAff /* OUT: Set to point to affinity string */
){
int nEq; /* The number of == or IN constraints to code */
Vdbe *v = pParse->pVdbe; /* The vm under construction */
Index *pIdx; /* The index being used for this loop */
WhereTerm *pTerm; /* A single constraint term */
WhereLoop *pLoop; /* The WhereLoop object */
int j; /* Loop counter */
int regBase; /* Base register */
int nReg; /* Number of registers to allocate */
char *zAff; /* Affinity string to return */
/* This module is only called on query plans that use an index. */
pLoop = pLevel->pWLoop;
assert( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0 );
nEq = pLoop->u.btree.nEq;
pIdx = pLoop->u.btree.pIndex;
assert( pIdx!=0 );
/* Figure out how many memory cells we will need then allocate them.
*/
regBase = pParse->nMem + 1;
nReg = pLoop->u.btree.nEq + nExtraReg;
pParse->nMem += nReg;
zAff = sqlite3DbStrDup(pParse->db, sqlite3IndexAffinityStr(v, pIdx));
if( !zAff ){
pParse->db->mallocFailed = 1;
}
/* Evaluate the equality constraints
*/
assert( zAff==0 || (int)strlen(zAff)>=nEq );
for(j=0; j<nEq; j++){
int r1;
pTerm = pLoop->aLTerm[j];
assert( pTerm!=0 );
/* The following true for indices with redundant columns.
** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
testcase( pTerm->wtFlags & TERM_VIRTUAL );
r1 = codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, regBase+j);
if( r1!=regBase+j ){
if( nReg==1 ){
sqlite3ReleaseTempReg(pParse, regBase);
regBase = r1;
}else{
sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
}
}
testcase( pTerm->eOperator & WO_ISNULL );
testcase( pTerm->eOperator & WO_IN );
if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
Expr *pRight = pTerm->pExpr->pRight;
sqlite3ExprCodeIsNullJump(v, pRight, regBase+j, pLevel->addrBrk);
if( zAff ){
if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_NONE ){
zAff[j] = SQLITE_AFF_NONE;
}
if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[j]) ){
zAff[j] = SQLITE_AFF_NONE;
}
}
}
}
*pzAff = zAff;
return regBase;
}
#ifndef SQLITE_OMIT_EXPLAIN
/*
** This routine is a helper for explainIndexRange() below
**
** pStr holds the text of an expression that we are building up one term
** at a time. This routine adds a new term to the end of the expression.
** Terms are separated by AND so add the "AND" text for second and subsequent
** terms only.
*/
static void explainAppendTerm(
StrAccum *pStr, /* The text expression being built */
int iTerm, /* Index of this term. First is zero */
const char *zColumn, /* Name of the column */
const char *zOp /* Name of the operator */
){
if( iTerm ) sqlite3StrAccumAppend(pStr, " AND ", 5);
sqlite3StrAccumAppend(pStr, zColumn, -1);
sqlite3StrAccumAppend(pStr, zOp, 1);
sqlite3StrAccumAppend(pStr, "?", 1);
}
/*
** Argument pLevel describes a strategy for scanning table pTab. This
** function returns a pointer to a string buffer containing a description
** of the subset of table rows scanned by the strategy in the form of an
** SQL expression. Or, if all rows are scanned, NULL is returned.
**
** For example, if the query:
**
** SELECT * FROM t1 WHERE a=1 AND b>2;
**
** is run and there is an index on (a, b), then this function returns a
** string similar to:
**
** "a=? AND b>?"
**
** The returned pointer points to memory obtained from sqlite3DbMalloc().
** It is the responsibility of the caller to free the buffer when it is
** no longer required.
*/
static char *explainIndexRange(sqlite3 *db, WhereLoop *pLoop, Table *pTab){
Index *pIndex = pLoop->u.btree.pIndex;
int nEq = pLoop->u.btree.nEq;
int i, j;
Column *aCol = pTab->aCol;
int *aiColumn = pIndex->aiColumn;
StrAccum txt;
if( nEq==0 && (pLoop->wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ){
return 0;
}
sqlite3StrAccumInit(&txt, 0, 0, SQLITE_MAX_LENGTH);
txt.db = db;
sqlite3StrAccumAppend(&txt, " (", 2);
for(i=0; i<nEq; i++){
char *z = (i==pIndex->nColumn ) ? "rowid" : aCol[aiColumn[i]].zName;
explainAppendTerm(&txt, i, z, "=");
}
j = i;
if( pLoop->wsFlags&WHERE_BTM_LIMIT ){
char *z = (j==pIndex->nColumn ) ? "rowid" : aCol[aiColumn[j]].zName;
explainAppendTerm(&txt, i++, z, ">");
}
if( pLoop->wsFlags&WHERE_TOP_LIMIT ){
char *z = (j==pIndex->nColumn ) ? "rowid" : aCol[aiColumn[j]].zName;
explainAppendTerm(&txt, i, z, "<");
}
sqlite3StrAccumAppend(&txt, ")", 1);
return sqlite3StrAccumFinish(&txt);
}
/*
** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
** command. If the query being compiled is an EXPLAIN QUERY PLAN, a single
** record is added to the output to describe the table scan strategy in
** pLevel.
*/
static void explainOneScan(
Parse *pParse, /* Parse context */
SrcList *pTabList, /* Table list this loop refers to */
WhereLevel *pLevel, /* Scan to write OP_Explain opcode for */
int iLevel, /* Value for "level" column of output */
int iFrom, /* Value for "from" column of output */
u16 wctrlFlags /* Flags passed to sqlite3WhereBegin() */
){
if( pParse->explain==2 ){
struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
Vdbe *v = pParse->pVdbe; /* VM being constructed */
sqlite3 *db = pParse->db; /* Database handle */
char *zMsg; /* Text to add to EQP output */
int iId = pParse->iSelectId; /* Select id (left-most output column) */
int isSearch; /* True for a SEARCH. False for SCAN. */
WhereLoop *pLoop; /* The controlling WhereLoop object */
u32 flags; /* Flags that describe this loop */
pLoop = pLevel->pWLoop;
flags = pLoop->wsFlags;
if( (flags&WHERE_MULTI_OR) || (wctrlFlags&WHERE_ONETABLE_ONLY) ) return;
isSearch = (flags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0
|| ((flags&WHERE_VIRTUALTABLE)==0 && (pLoop->u.btree.nEq>0))
|| (wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX));
zMsg = sqlite3MPrintf(db, "%s", isSearch?"SEARCH":"SCAN");
if( pItem->pSelect ){
zMsg = sqlite3MAppendf(db, zMsg, "%s SUBQUERY %d", zMsg,pItem->iSelectId);
}else{
zMsg = sqlite3MAppendf(db, zMsg, "%s TABLE %s", zMsg, pItem->zName);
}
if( pItem->zAlias ){
zMsg = sqlite3MAppendf(db, zMsg, "%s AS %s", zMsg, pItem->zAlias);
}
if( (flags & (WHERE_IPK|WHERE_VIRTUALTABLE))==0
&& ALWAYS(pLoop->u.btree.pIndex!=0)
){
char *zWhere = explainIndexRange(db, pLoop, pItem->pTab);
zMsg = sqlite3MAppendf(db, zMsg,
((flags & WHERE_AUTO_INDEX) ?
"%s USING AUTOMATIC %sINDEX%.0s%s" :
"%s USING %sINDEX %s%s"),
zMsg, ((flags & WHERE_IDX_ONLY) ? "COVERING " : ""),
pLoop->u.btree.pIndex->zName, zWhere);
sqlite3DbFree(db, zWhere);
}else if( (flags & WHERE_IPK)!=0 && (flags & WHERE_CONSTRAINT)!=0 ){
zMsg = sqlite3MAppendf(db, zMsg, "%s USING INTEGER PRIMARY KEY", zMsg);
if( flags&(WHERE_COLUMN_EQ|WHERE_COLUMN_IN) ){
zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid=?)", zMsg);
}else if( (flags&WHERE_BOTH_LIMIT)==WHERE_BOTH_LIMIT ){
zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid>? AND rowid<?)", zMsg);
}else if( flags&WHERE_BTM_LIMIT ){
zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid>?)", zMsg);
}else if( ALWAYS(flags&WHERE_TOP_LIMIT) ){
zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid<?)", zMsg);
}
}
#ifndef SQLITE_OMIT_VIRTUALTABLE
else if( (flags & WHERE_VIRTUALTABLE)!=0 ){
zMsg = sqlite3MAppendf(db, zMsg, "%s VIRTUAL TABLE INDEX %d:%s", zMsg,
pLoop->u.vtab.idxNum, pLoop->u.vtab.idxStr);
}
#endif
zMsg = sqlite3MAppendf(db, zMsg, "%s", zMsg);
sqlite3VdbeAddOp4(v, OP_Explain, iId, iLevel, iFrom, zMsg, P4_DYNAMIC);
}
}
#else
# define explainOneScan(u,v,w,x,y,z)
#endif /* SQLITE_OMIT_EXPLAIN */
/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
*/
static Bitmask codeOneLoopStart(
WhereInfo *pWInfo, /* Complete information about the WHERE clause */
int iLevel, /* Which level of pWInfo->a[] should be coded */
Bitmask notReady /* Which tables are currently available */
){
int j, k; /* Loop counters */
int iCur; /* The VDBE cursor for the table */
int addrNxt; /* Where to jump to continue with the next IN case */
int omitTable; /* True if we use the index only */
int bRev; /* True if we need to scan in reverse order */
WhereLevel *pLevel; /* The where level to be coded */
WhereLoop *pLoop; /* The WhereLoop object being coded */
WhereClause *pWC; /* Decomposition of the entire WHERE clause */
WhereTerm *pTerm; /* A WHERE clause term */
Parse *pParse; /* Parsing context */
sqlite3 *db; /* Database connection */
Vdbe *v; /* The prepared stmt under constructions */
struct SrcList_item *pTabItem; /* FROM clause term being coded */
int addrBrk; /* Jump here to break out of the loop */
int addrCont; /* Jump here to continue with next cycle */
int iRowidReg = 0; /* Rowid is stored in this register, if not zero */
int iReleaseReg = 0; /* Temp register to free before returning */
pParse = pWInfo->pParse;
v = pParse->pVdbe;
pWC = &pWInfo->sWC;
db = pParse->db;
pLevel = &pWInfo->a[iLevel];
pLoop = pLevel->pWLoop;
pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
iCur = pTabItem->iCursor;
pLevel->notReady = notReady & ~getMask(&pWInfo->sMaskSet, iCur);
bRev = (pWInfo->revMask>>iLevel)&1;
omitTable = (pLoop->wsFlags & WHERE_IDX_ONLY)!=0
&& (pWInfo->wctrlFlags & WHERE_FORCE_TABLE)==0;
VdbeNoopComment((v, "Begin Join Loop %d", iLevel));
/* Create labels for the "break" and "continue" instructions
** for the current loop. Jump to addrBrk to break out of a loop.
** Jump to cont to go immediately to the next iteration of the
** loop.
**
** When there is an IN operator, we also have a "addrNxt" label that
** means to continue with the next IN value combination. When
** there are no IN operators in the constraints, the "addrNxt" label
** is the same as "addrBrk".
*/
addrBrk = pLevel->addrBrk = pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
addrCont = pLevel->addrCont = sqlite3VdbeMakeLabel(v);
/* If this is the right table of a LEFT OUTER JOIN, allocate and
** initialize a memory cell that records if this table matches any
** row of the left table of the join.
*/
if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
pLevel->iLeftJoin = ++pParse->nMem;
sqlite3VdbeAddOp2(v, OP_Integer, 0, pLevel->iLeftJoin);
VdbeComment((v, "init LEFT JOIN no-match flag"));
}
/* Special case of a FROM clause subquery implemented as a co-routine */
if( pTabItem->viaCoroutine ){
int regYield = pTabItem->regReturn;
sqlite3VdbeAddOp2(v, OP_Integer, pTabItem->addrFillSub-1, regYield);
pLevel->p2 = sqlite3VdbeAddOp1(v, OP_Yield, regYield);
VdbeComment((v, "next row of co-routine %s", pTabItem->pTab->zName));
sqlite3VdbeAddOp2(v, OP_If, regYield+1, addrBrk);
pLevel->op = OP_Goto;
}else
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
/* Case 1: The table is a virtual-table. Use the VFilter and VNext
** to access the data.
*/
int iReg; /* P3 Value for OP_VFilter */
int addrNotFound;
int nConstraint = pLoop->nLTerm;
sqlite3ExprCachePush(pParse);
iReg = sqlite3GetTempRange(pParse, nConstraint+2);
addrNotFound = pLevel->addrBrk;
for(j=0; j<nConstraint; j++){
int iTarget = iReg+j+2;
pTerm = pLoop->aLTerm[j];
if( pTerm==0 ) continue;
if( pTerm->eOperator & WO_IN ){
codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, iTarget);
addrNotFound = pLevel->addrNxt;
}else{
sqlite3ExprCode(pParse, pTerm->pExpr->pRight, iTarget);
}
}
sqlite3VdbeAddOp2(v, OP_Integer, pLoop->u.vtab.idxNum, iReg);
sqlite3VdbeAddOp2(v, OP_Integer, nConstraint, iReg+1);
sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrNotFound, iReg,
pLoop->u.vtab.idxStr,
pLoop->u.vtab.needFree ? P4_MPRINTF : P4_STATIC);
pLoop->u.vtab.needFree = 0;
for(j=0; j<nConstraint && j<16; j++){
if( (pLoop->u.vtab.omitMask>>j)&1 ){
disableTerm(pLevel, pLoop->aLTerm[j]);
}
}
pLevel->op = OP_VNext;
pLevel->p1 = iCur;
pLevel->p2 = sqlite3VdbeCurrentAddr(v);
sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
sqlite3ExprCachePop(pParse, 1);
}else
#endif /* SQLITE_OMIT_VIRTUALTABLE */
if( (pLoop->wsFlags & WHERE_IPK)!=0
&& (pLoop->wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_EQ))!=0
){
/* Case 2: We can directly reference a single row using an
** equality comparison against the ROWID field. Or
** we reference multiple rows using a "rowid IN (...)"
** construct.
*/
assert( pLoop->u.btree.nEq==1 );
iReleaseReg = sqlite3GetTempReg(pParse);
pTerm = pLoop->aLTerm[0];
assert( pTerm!=0 );
assert( pTerm->pExpr!=0 );
assert( omitTable==0 );
testcase( pTerm->wtFlags & TERM_VIRTUAL );
iRowidReg = codeEqualityTerm(pParse, pTerm, pLevel, 0, bRev, iReleaseReg);
addrNxt = pLevel->addrNxt;
sqlite3VdbeAddOp2(v, OP_MustBeInt, iRowidReg, addrNxt);
sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, iRowidReg);
sqlite3ExprCacheAffinityChange(pParse, iRowidReg, 1);
sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
VdbeComment((v, "pk"));
pLevel->op = OP_Noop;
}else if( (pLoop->wsFlags & WHERE_IPK)!=0
&& (pLoop->wsFlags & WHERE_COLUMN_RANGE)!=0
){
/* Case 3: We have an inequality comparison against the ROWID field.
*/
int testOp = OP_Noop;
int start;
int memEndValue = 0;
WhereTerm *pStart, *pEnd;
assert( omitTable==0 );
j = 0;
pStart = pEnd = 0;
if( pLoop->wsFlags & WHERE_BTM_LIMIT ) pStart = pLoop->aLTerm[j++];
if( pLoop->wsFlags & WHERE_TOP_LIMIT ) pEnd = pLoop->aLTerm[j++];
assert( pStart!=0 || pEnd!=0 );
if( bRev ){
pTerm = pStart;
pStart = pEnd;
pEnd = pTerm;
}
if( pStart ){
Expr *pX; /* The expression that defines the start bound */
int r1, rTemp; /* Registers for holding the start boundary */
/* The following constant maps TK_xx codes into corresponding
** seek opcodes. It depends on a particular ordering of TK_xx
*/
const u8 aMoveOp[] = {
/* TK_GT */ OP_SeekGt,
/* TK_LE */ OP_SeekLe,
/* TK_LT */ OP_SeekLt,
/* TK_GE */ OP_SeekGe
};
assert( TK_LE==TK_GT+1 ); /* Make sure the ordering.. */
assert( TK_LT==TK_GT+2 ); /* ... of the TK_xx values... */
assert( TK_GE==TK_GT+3 ); /* ... is correcct. */
assert( (pStart->wtFlags & TERM_VNULL)==0 );
testcase( pStart->wtFlags & TERM_VIRTUAL );
pX = pStart->pExpr;
assert( pX!=0 );
testcase( pStart->leftCursor!=iCur ); /* transitive constraints */
r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, &rTemp);
sqlite3VdbeAddOp3(v, aMoveOp[pX->op-TK_GT], iCur, addrBrk, r1);
VdbeComment((v, "pk"));
sqlite3ExprCacheAffinityChange(pParse, r1, 1);
sqlite3ReleaseTempReg(pParse, rTemp);
disableTerm(pLevel, pStart);
}else{
sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, addrBrk);
}
if( pEnd ){
Expr *pX;
pX = pEnd->pExpr;
assert( pX!=0 );
assert( (pEnd->wtFlags & TERM_VNULL)==0 );
testcase( pEnd->leftCursor!=iCur ); /* Transitive constraints */
testcase( pEnd->wtFlags & TERM_VIRTUAL );
memEndValue = ++pParse->nMem;
sqlite3ExprCode(pParse, pX->pRight, memEndValue);
if( pX->op==TK_LT || pX->op==TK_GT ){
testOp = bRev ? OP_Le : OP_Ge;
}else{
testOp = bRev ? OP_Lt : OP_Gt;
}
disableTerm(pLevel, pEnd);
}
start = sqlite3VdbeCurrentAddr(v);
pLevel->op = bRev ? OP_Prev : OP_Next;
pLevel->p1 = iCur;
pLevel->p2 = start;
assert( pLevel->p5==0 );
if( testOp!=OP_Noop ){
iRowidReg = iReleaseReg = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, iRowidReg);
sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
}
}else if( pLoop->wsFlags & WHERE_INDEXED ){
/* Case 4: A scan using an index.
**
** The WHERE clause may contain zero or more equality
** terms ("==" or "IN" operators) that refer to the N
** left-most columns of the index. It may also contain
** inequality constraints (>, <, >= or <=) on the indexed
** column that immediately follows the N equalities. Only
** the right-most column can be an inequality - the rest must
** use the "==" and "IN" operators. For example, if the
** index is on (x,y,z), then the following clauses are all
** optimized:
**
** x=5
** x=5 AND y=10
** x=5 AND y<10
** x=5 AND y>5 AND y<10
** x=5 AND y=5 AND z<=10
**
** The z<10 term of the following cannot be used, only
** the x=5 term:
**
** x=5 AND z<10
**
** N may be zero if there are inequality constraints.
** If there are no inequality constraints, then N is at
** least one.
**
** This case is also used when there are no WHERE clause
** constraints but an index is selected anyway, in order
** to force the output order to conform to an ORDER BY.
*/
static const u8 aStartOp[] = {
0,
0,
OP_Rewind, /* 2: (!start_constraints && startEq && !bRev) */
OP_Last, /* 3: (!start_constraints && startEq && bRev) */
OP_SeekGt, /* 4: (start_constraints && !startEq && !bRev) */
OP_SeekLt, /* 5: (start_constraints && !startEq && bRev) */
OP_SeekGe, /* 6: (start_constraints && startEq && !bRev) */
OP_SeekLe /* 7: (start_constraints && startEq && bRev) */
};
static const u8 aEndOp[] = {
OP_Noop, /* 0: (!end_constraints) */
OP_IdxGE, /* 1: (end_constraints && !bRev) */
OP_IdxLT /* 2: (end_constraints && bRev) */
};
int nEq = pLoop->u.btree.nEq; /* Number of == or IN terms */
int isMinQuery = 0; /* If this is an optimized SELECT min(x).. */
int regBase; /* Base register holding constraint values */
int r1; /* Temp register */
WhereTerm *pRangeStart = 0; /* Inequality constraint at range start */
WhereTerm *pRangeEnd = 0; /* Inequality constraint at range end */
int startEq; /* True if range start uses ==, >= or <= */
int endEq; /* True if range end uses ==, >= or <= */
int start_constraints; /* Start of range is constrained */
int nConstraint; /* Number of constraint terms */
Index *pIdx; /* The index we will be using */
int iIdxCur; /* The VDBE cursor for the index */
int nExtraReg = 0; /* Number of extra registers needed */
int op; /* Instruction opcode */
char *zStartAff; /* Affinity for start of range constraint */
char *zEndAff; /* Affinity for end of range constraint */
pIdx = pLoop->u.btree.pIndex;
iIdxCur = pLevel->iIdxCur;
/* If this loop satisfies a sort order (pOrderBy) request that
** was passed to this function to implement a "SELECT min(x) ..."
** query, then the caller will only allow the loop to run for
** a single iteration. This means that the first row returned
** should not have a NULL value stored in 'x'. If column 'x' is
** the first one after the nEq equality constraints in the index,
** this requires some special handling.
*/
if( (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)!=0
&& (pWInfo->bOBSat!=0)
&& (pIdx->nColumn>nEq)
){
/* assert( pOrderBy->nExpr==1 ); */
/* assert( pOrderBy->a[0].pExpr->iColumn==pIdx->aiColumn[nEq] ); */
isMinQuery = 1;
nExtraReg = 1;
}
/* Find any inequality constraint terms for the start and end
** of the range.
*/
j = nEq;
if( pLoop->wsFlags & WHERE_BTM_LIMIT ){
pRangeStart = pLoop->aLTerm[j++];
nExtraReg = 1;
}
if( pLoop->wsFlags & WHERE_TOP_LIMIT ){
pRangeEnd = pLoop->aLTerm[j++];
nExtraReg = 1;
}
/* Generate code to evaluate all constraint terms using == or IN
** and store the values of those terms in an array of registers
** starting at regBase.
*/
regBase = codeAllEqualityTerms(pParse,pLevel,bRev,nExtraReg,&zStartAff);
zEndAff = sqlite3DbStrDup(db, zStartAff);
addrNxt = pLevel->addrNxt;
/* If we are doing a reverse order scan on an ascending index, or
** a forward order scan on a descending index, interchange the
** start and end terms (pRangeStart and pRangeEnd).
*/
if( (nEq<pIdx->nColumn && bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC))
|| (bRev && pIdx->nColumn==nEq)
){
SWAP(WhereTerm *, pRangeEnd, pRangeStart);
}
testcase( pRangeStart && (pRangeStart->eOperator & WO_LE)!=0 );
testcase( pRangeStart && (pRangeStart->eOperator & WO_GE)!=0 );
testcase( pRangeEnd && (pRangeEnd->eOperator & WO_LE)!=0 );
testcase( pRangeEnd && (pRangeEnd->eOperator & WO_GE)!=0 );
startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
endEq = !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
start_constraints = pRangeStart || nEq>0;
/* Seek the index cursor to the start of the range. */
nConstraint = nEq;
if( pRangeStart ){
Expr *pRight = pRangeStart->pExpr->pRight;
sqlite3ExprCode(pParse, pRight, regBase+nEq);
if( (pRangeStart->wtFlags & TERM_VNULL)==0 ){
sqlite3ExprCodeIsNullJump(v, pRight, regBase+nEq, addrNxt);
}
if( zStartAff ){
if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_NONE){
/* Since the comparison is to be performed with no conversions
** applied to the operands, set the affinity to apply to pRight to
** SQLITE_AFF_NONE. */
zStartAff[nEq] = SQLITE_AFF_NONE;
}
if( sqlite3ExprNeedsNoAffinityChange(pRight, zStartAff[nEq]) ){
zStartAff[nEq] = SQLITE_AFF_NONE;
}
}
nConstraint++;
testcase( pRangeStart->wtFlags & TERM_VIRTUAL );
}else if( isMinQuery ){
sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
nConstraint++;
startEq = 0;
start_constraints = 1;
}
codeApplyAffinity(pParse, regBase, nConstraint, zStartAff);
op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
assert( op!=0 );
testcase( op==OP_Rewind );
testcase( op==OP_Last );
testcase( op==OP_SeekGt );
testcase( op==OP_SeekGe );
testcase( op==OP_SeekLe );
testcase( op==OP_SeekLt );
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
/* Load the value for the inequality constraint at the end of the
** range (if any).
*/
nConstraint = nEq;
if( pRangeEnd ){
Expr *pRight = pRangeEnd->pExpr->pRight;
sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
sqlite3ExprCode(pParse, pRight, regBase+nEq);
if( (pRangeEnd->wtFlags & TERM_VNULL)==0 ){
sqlite3ExprCodeIsNullJump(v, pRight, regBase+nEq, addrNxt);
}
if( zEndAff ){
if( sqlite3CompareAffinity(pRight, zEndAff[nEq])==SQLITE_AFF_NONE){
/* Since the comparison is to be performed with no conversions
** applied to the operands, set the affinity to apply to pRight to
** SQLITE_AFF_NONE. */
zEndAff[nEq] = SQLITE_AFF_NONE;
}
if( sqlite3ExprNeedsNoAffinityChange(pRight, zEndAff[nEq]) ){
zEndAff[nEq] = SQLITE_AFF_NONE;
}
}
codeApplyAffinity(pParse, regBase, nEq+1, zEndAff);
nConstraint++;
testcase( pRangeEnd->wtFlags & TERM_VIRTUAL );
}
sqlite3DbFree(db, zStartAff);
sqlite3DbFree(db, zEndAff);
/* Top of the loop body */
pLevel->p2 = sqlite3VdbeCurrentAddr(v);
/* Check if the index cursor is past the end of the range. */
op = aEndOp[(pRangeEnd || nEq) * (1 + bRev)];
testcase( op==OP_Noop );
testcase( op==OP_IdxGE );
testcase( op==OP_IdxLT );
if( op!=OP_Noop ){
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
sqlite3VdbeChangeP5(v, endEq!=bRev ?1:0);
}
/* If there are inequality constraints, check that the value
** of the table column that the inequality contrains is not NULL.
** If it is, jump to the next iteration of the loop.
*/
r1 = sqlite3GetTempReg(pParse);
testcase( pLoop->wsFlags & WHERE_BTM_LIMIT );
testcase( pLoop->wsFlags & WHERE_TOP_LIMIT );
if( (pLoop->wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0 ){
sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, nEq, r1);
sqlite3VdbeAddOp2(v, OP_IsNull, r1, addrCont);
}
sqlite3ReleaseTempReg(pParse, r1);
/* Seek the table cursor, if required */
disableTerm(pLevel, pRangeStart);
disableTerm(pLevel, pRangeEnd);
if( !omitTable ){
iRowidReg = iReleaseReg = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, iRowidReg);
sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
sqlite3VdbeAddOp2(v, OP_Seek, iCur, iRowidReg); /* Deferred seek */
}
/* Record the instruction used to terminate the loop. Disable
** WHERE clause terms made redundant by the index range scan.
*/
if( pLoop->wsFlags & WHERE_ONEROW ){
pLevel->op = OP_Noop;
}else if( bRev ){
pLevel->op = OP_Prev;
}else{
pLevel->op = OP_Next;
}
pLevel->p1 = iIdxCur;
if( (pLoop->wsFlags & WHERE_CONSTRAINT)==0 ){
pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
}else{
assert( pLevel->p5==0 );
}
}else
#ifndef SQLITE_OMIT_OR_OPTIMIZATION
if( pLoop->wsFlags & WHERE_MULTI_OR ){
/* Case 5: Two or more separately indexed terms connected by OR
**
** Example:
**
** CREATE TABLE t1(a,b,c,d);
** CREATE INDEX i1 ON t1(a);
** CREATE INDEX i2 ON t1(b);
** CREATE INDEX i3 ON t1(c);
**
** SELECT * FROM t1 WHERE a=5 OR b=7 OR (c=11 AND d=13)
**
** In the example, there are three indexed terms connected by OR.
** The top of the loop looks like this:
**
** Null 1 # Zero the rowset in reg 1
**
** Then, for each indexed term, the following. The arguments to
** RowSetTest are such that the rowid of the current row is inserted
** into the RowSet. If it is already present, control skips the
** Gosub opcode and jumps straight to the code generated by WhereEnd().
**
** sqlite3WhereBegin(<term>)
** RowSetTest # Insert rowid into rowset
** Gosub 2 A
** sqlite3WhereEnd()
**
** Following the above, code to terminate the loop. Label A, the target
** of the Gosub above, jumps to the instruction right after the Goto.
**
** Null 1 # Zero the rowset in reg 1
** Goto B # The loop is finished.
**
** A: <loop body> # Return data, whatever.
**
** Return 2 # Jump back to the Gosub
**
** B: <after the loop>
**
*/
WhereClause *pOrWc; /* The OR-clause broken out into subterms */
SrcList *pOrTab; /* Shortened table list or OR-clause generation */
Index *pCov = 0; /* Potential covering index (or NULL) */
int iCovCur = pParse->nTab++; /* Cursor used for index scans (if any) */
int regReturn = ++pParse->nMem; /* Register used with OP_Gosub */
int regRowset = 0; /* Register for RowSet object */
int regRowid = 0; /* Register holding rowid */
int iLoopBody = sqlite3VdbeMakeLabel(v); /* Start of loop body */
int iRetInit; /* Address of regReturn init */
int untestedTerms = 0; /* Some terms not completely tested */
int ii; /* Loop counter */
Expr *pAndExpr = 0; /* An ".. AND (...)" expression */
pTerm = pLoop->aLTerm[0];
assert( pTerm!=0 );
assert( pTerm->eOperator & WO_OR );
assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
pOrWc = &pTerm->u.pOrInfo->wc;
pLevel->op = OP_Return;
pLevel->p1 = regReturn;
/* Set up a new SrcList in pOrTab containing the table being scanned
** by this loop in the a[0] slot and all notReady tables in a[1..] slots.
** This becomes the SrcList in the recursive call to sqlite3WhereBegin().
*/
if( pWInfo->nLevel>1 ){
int nNotReady; /* The number of notReady tables */
struct SrcList_item *origSrc; /* Original list of tables */
nNotReady = pWInfo->nLevel - iLevel - 1;
pOrTab = sqlite3StackAllocRaw(db,
sizeof(*pOrTab)+ nNotReady*sizeof(pOrTab->a[0]));
if( pOrTab==0 ) return notReady;
pOrTab->nAlloc = (u8)(nNotReady + 1);
pOrTab->nSrc = pOrTab->nAlloc;
memcpy(pOrTab->a, pTabItem, sizeof(*pTabItem));
origSrc = pWInfo->pTabList->a;
for(k=1; k<=nNotReady; k++){
memcpy(&pOrTab->a[k], &origSrc[pLevel[k].iFrom], sizeof(pOrTab->a[k]));
}
}else{
pOrTab = pWInfo->pTabList;
}
/* Initialize the rowset register to contain NULL. An SQL NULL is
** equivalent to an empty rowset.
**
** Also initialize regReturn to contain the address of the instruction
** immediately following the OP_Return at the bottom of the loop. This
** is required in a few obscure LEFT JOIN cases where control jumps
** over the top of the loop into the body of it. In this case the
** correct response for the end-of-loop code (the OP_Return) is to
** fall through to the next instruction, just as an OP_Next does if
** called on an uninitialized cursor.
*/
if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
regRowset = ++pParse->nMem;
regRowid = ++pParse->nMem;
sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
}
iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);
/* If the original WHERE clause is z of the form: (x1 OR x2 OR ...) AND y
** Then for every term xN, evaluate as the subexpression: xN AND z
** That way, terms in y that are factored into the disjunction will
** be picked up by the recursive calls to sqlite3WhereBegin() below.
**
** Actually, each subexpression is converted to "xN AND w" where w is
** the "interesting" terms of z - terms that did not originate in the
** ON or USING clause of a LEFT JOIN, and terms that are usable as
** indices.
**
** This optimization also only applies if the (x1 OR x2 OR ...) term
** is not contained in the ON clause of a LEFT JOIN.
** See ticket http://www.sqlite.org/src/info/f2369304e4
*/
if( pWC->nTerm>1 ){
int iTerm;
for(iTerm=0; iTerm<pWC->nTerm; iTerm++){
Expr *pExpr = pWC->a[iTerm].pExpr;
if( &pWC->a[iTerm] == pTerm ) continue;
if( ExprHasProperty(pExpr, EP_FromJoin) ) continue;
if( pWC->a[iTerm].wtFlags & (TERM_ORINFO) ) continue;
if( (pWC->a[iTerm].eOperator & WO_ALL)==0 ) continue;
pExpr = sqlite3ExprDup(db, pExpr, 0);
pAndExpr = sqlite3ExprAnd(db, pAndExpr, pExpr);
}
if( pAndExpr ){
pAndExpr = sqlite3PExpr(pParse, TK_AND, 0, pAndExpr, 0);
}
}
for(ii=0; ii<pOrWc->nTerm; ii++){
WhereTerm *pOrTerm = &pOrWc->a[ii];
if( pOrTerm->leftCursor==iCur || (pOrTerm->eOperator & WO_AND)!=0 ){
WhereInfo *pSubWInfo; /* Info for single OR-term scan */
Expr *pOrExpr = pOrTerm->pExpr;
if( pAndExpr && !ExprHasProperty(pOrExpr, EP_FromJoin) ){
pAndExpr->pLeft = pOrExpr;
pOrExpr = pAndExpr;
}
/* Loop through table entries that match term pOrTerm. */
pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
WHERE_OMIT_OPEN_CLOSE | WHERE_AND_ONLY |
WHERE_FORCE_TABLE | WHERE_ONETABLE_ONLY, iCovCur);
assert( pSubWInfo || pParse->nErr || db->mallocFailed );
if( pSubWInfo ){
WhereLoop *pSubLoop;
explainOneScan(
pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
);
if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
int r;
r = sqlite3ExprCodeGetColumn(pParse, pTabItem->pTab, -1, iCur,
regRowid, 0);
sqlite3VdbeAddOp4Int(v, OP_RowSetTest, regRowset,
sqlite3VdbeCurrentAddr(v)+2, r, iSet);
}
sqlite3VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);
/* The pSubWInfo->untestedTerms flag means that this OR term
** contained one or more AND term from a notReady table. The
** terms from the notReady table could not be tested and will
** need to be tested later.
*/
if( pSubWInfo->untestedTerms ) untestedTerms = 1;
/* If all of the OR-connected terms are optimized using the same
** index, and the index is opened using the same cursor number
** by each call to sqlite3WhereBegin() made by this loop, it may
** be possible to use that index as a covering index.
**
** If the call to sqlite3WhereBegin() above resulted in a scan that
** uses an index, and this is either the first OR-connected term
** processed or the index is the same as that used by all previous
** terms, set pCov to the candidate covering index. Otherwise, set
** pCov to NULL to indicate that no candidate covering index will
** be available.
*/
pSubLoop = pSubWInfo->a[0].pWLoop;
assert( (pSubLoop->wsFlags & WHERE_AUTO_INDEX)==0 );
if( (pSubLoop->wsFlags & WHERE_INDEXED)!=0
&& (ii==0 || pSubLoop->u.btree.pIndex==pCov)
){
assert( pSubWInfo->a[0].iIdxCur==iCovCur );
pCov = pSubLoop->u.btree.pIndex;
}else{
pCov = 0;
}
/* Finish the loop through table entries that match term pOrTerm. */
sqlite3WhereEnd(pSubWInfo);
}
}
}
pLevel->u.pCovidx = pCov;
if( pCov ) pLevel->iIdxCur = iCovCur;
if( pAndExpr ){
pAndExpr->pLeft = 0;
sqlite3ExprDelete(db, pAndExpr);
}
sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrBrk);
sqlite3VdbeResolveLabel(v, iLoopBody);
if( pWInfo->nLevel>1 ) sqlite3StackFree(db, pOrTab);
if( !untestedTerms ) disableTerm(pLevel, pTerm);
}else
#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
{
/* Case 6: There is no usable index. We must do a complete
** scan of the entire table.
*/
static const u8 aStep[] = { OP_Next, OP_Prev };
static const u8 aStart[] = { OP_Rewind, OP_Last };
assert( bRev==0 || bRev==1 );
pLevel->op = aStep[bRev];
pLevel->p1 = iCur;
pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
}
/* Insert code to test every subexpression that can be completely
** computed using the current set of tables.
*/
for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
Expr *pE;
testcase( pTerm->wtFlags & TERM_VIRTUAL );
testcase( pTerm->wtFlags & TERM_CODED );
if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
testcase( pWInfo->untestedTerms==0
&& (pWInfo->wctrlFlags & WHERE_ONETABLE_ONLY)!=0 );
pWInfo->untestedTerms = 1;
continue;
}
pE = pTerm->pExpr;
assert( pE!=0 );
if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
continue;
}
sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
pTerm->wtFlags |= TERM_CODED;
}
/* Insert code to test for implied constraints based on transitivity
** of the "==" operator.
**
** Example: If the WHERE clause contains "t1.a=t2.b" and "t2.b=123"
** and we are coding the t1 loop and the t2 loop has not yet coded,
** then we cannot use the "t1.a=t2.b" constraint, but we can code
** the implied "t1.a=123" constraint.
*/
for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
Expr *pE, *pEAlt;
WhereTerm *pAlt;
if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
if( pTerm->eOperator!=(WO_EQUIV|WO_EQ) ) continue;
if( pTerm->leftCursor!=iCur ) continue;
if( pLevel->iLeftJoin ) continue;
pE = pTerm->pExpr;
assert( !ExprHasProperty(pE, EP_FromJoin) );
assert( (pTerm->prereqRight & pLevel->notReady)!=0 );
pAlt = findTerm(pWC, iCur, pTerm->u.leftColumn, notReady, WO_EQ|WO_IN, 0);
if( pAlt==0 ) continue;
if( pAlt->wtFlags & (TERM_CODED) ) continue;
testcase( pAlt->eOperator & WO_EQ );
testcase( pAlt->eOperator & WO_IN );
VdbeNoopComment((v, "begin transitive constraint"));
pEAlt = sqlite3StackAllocRaw(db, sizeof(*pEAlt));
if( pEAlt ){
*pEAlt = *pAlt->pExpr;
pEAlt->pLeft = pE->pLeft;
sqlite3ExprIfFalse(pParse, pEAlt, addrCont, SQLITE_JUMPIFNULL);
sqlite3StackFree(db, pEAlt);
}
}
/* For a LEFT OUTER JOIN, generate code that will record the fact that
** at least one row of the right table has matched the left table.
*/
if( pLevel->iLeftJoin ){
pLevel->addrFirst = sqlite3VdbeCurrentAddr(v);
sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
VdbeComment((v, "record LEFT JOIN hit"));
sqlite3ExprCacheClear(pParse);
for(pTerm=pWC->a, j=0; j<pWC->nTerm; j++, pTerm++){
testcase( pTerm->wtFlags & TERM_VIRTUAL );
testcase( pTerm->wtFlags & TERM_CODED );
if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
assert( pWInfo->untestedTerms );
continue;
}
assert( pTerm->pExpr );
sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
pTerm->wtFlags |= TERM_CODED;
}
}
sqlite3ReleaseTempReg(pParse, iReleaseReg);
return pLevel->notReady;
}
#ifdef WHERETRACE_ENABLED
/*
** Print a WhereLoop object for debugging purposes
*/
static void whereLoopPrint(WhereLoop *p, SrcList *pTabList){
int nb = 1+(pTabList->nSrc+7)/8;
struct SrcList_item *pItem = pTabList->a + p->iTab;
Table *pTab = pItem->pTab;
sqlite3DebugPrintf("%c%2d.%0*llx.%0*llx", p->cId,
p->iTab, nb, p->maskSelf, nb, p->prereq);
sqlite3DebugPrintf(" %12s",
pItem->zAlias ? pItem->zAlias : pTab->zName);
if( (p->wsFlags & WHERE_VIRTUALTABLE)==0 ){
if( p->u.btree.pIndex ){
const char *zName = p->u.btree.pIndex->zName;
if( zName==0 ) zName = "ipk";
if( strncmp(zName, "sqlite_autoindex_", 17)==0 ){
int i = sqlite3Strlen30(zName) - 1;
while( zName[i]!='_' ) i--;
zName += i;
}
sqlite3DebugPrintf(".%-16s %2d", zName, p->u.btree.nEq);
}else{
sqlite3DebugPrintf("%20s","");
}
}else{
char *z;
if( p->u.vtab.idxStr ){
z = sqlite3_mprintf("(%d,\"%s\",%x)",
p->u.vtab.idxNum, p->u.vtab.idxStr, p->u.vtab.omitMask);
}else{
z = sqlite3_mprintf("(%d,%x)", p->u.vtab.idxNum, p->u.vtab.omitMask);
}
sqlite3DebugPrintf(" %-19s", z);
sqlite3_free(z);
}
sqlite3DebugPrintf(" f %04x N %d", p->wsFlags, p->nLTerm);
sqlite3DebugPrintf(" cost %d,%d,%d\n", p->rSetup, p->rRun, p->nOut);
}
#endif
/*
** Convert bulk memory into a valid WhereLoop that can be passed
** to whereLoopClear harmlessly.
*/
static void whereLoopInit(WhereLoop *p){
p->aLTerm = p->aLTermSpace;
p->nLTerm = 0;
p->nLSlot = ArraySize(p->aLTermSpace);
p->wsFlags = 0;
}
/*
** Clear the WhereLoop.u union. Leave WhereLoop.pLTerm intact.
*/
static void whereLoopClearUnion(sqlite3 *db, WhereLoop *p){
if( p->wsFlags & (WHERE_VIRTUALTABLE|WHERE_AUTO_INDEX) ){
if( (p->wsFlags & WHERE_VIRTUALTABLE)!=0 && p->u.vtab.needFree ){
sqlite3_free(p->u.vtab.idxStr);
p->u.vtab.needFree = 0;
p->u.vtab.idxStr = 0;
}else if( (p->wsFlags & WHERE_AUTO_INDEX)!=0 && p->u.btree.pIndex!=0 ){
sqlite3DbFree(db, p->u.btree.pIndex->zColAff);
sqlite3DbFree(db, p->u.btree.pIndex);
p->u.btree.pIndex = 0;
}
}
}
/*
** Deallocate internal memory used by a WhereLoop object
*/
static void whereLoopClear(sqlite3 *db, WhereLoop *p){
if( p->aLTerm!=p->aLTermSpace ) sqlite3DbFree(db, p->aLTerm);
whereLoopClearUnion(db, p);
whereLoopInit(p);
}
/*
** Increase the memory allocation for pLoop->aLTerm[] to be at least n.
*/
static int whereLoopResize(sqlite3 *db, WhereLoop *p, int n){
WhereTerm **paNew;
if( p->nLSlot>=n ) return SQLITE_OK;
n = (n+7)&~7;
paNew = sqlite3DbMallocRaw(db, sizeof(p->aLTerm[0])*n);
if( paNew==0 ) return SQLITE_NOMEM;
memcpy(paNew, p->aLTerm, sizeof(p->aLTerm[0])*p->nLSlot);
if( p->aLTerm!=p->aLTermSpace ) sqlite3DbFree(db, p->aLTerm);
p->aLTerm = paNew;
p->nLSlot = n;
return SQLITE_OK;
}
/*
** Transfer content from the second pLoop into the first.
*/
static int whereLoopXfer(sqlite3 *db, WhereLoop *pTo, WhereLoop *pFrom){
whereLoopClearUnion(db, pTo);
if( whereLoopResize(db, pTo, pFrom->nLTerm) ){
memset(&pTo->u, 0, sizeof(pTo->u));
return SQLITE_NOMEM;
}
memcpy(pTo, pFrom, WHERE_LOOP_XFER_SZ);
memcpy(pTo->aLTerm, pFrom->aLTerm, pTo->nLTerm*sizeof(pTo->aLTerm[0]));
if( pFrom->wsFlags & WHERE_VIRTUALTABLE ){
pFrom->u.vtab.needFree = 0;
}else if( (pFrom->wsFlags & WHERE_AUTO_INDEX)!=0 ){
pFrom->u.btree.pIndex = 0;
}
return SQLITE_OK;
}
/*
** Delete a WhereLoop object
*/
static void whereLoopDelete(sqlite3 *db, WhereLoop *p){
whereLoopClear(db, p);
sqlite3DbFree(db, p);
}
/*
** Free a WhereInfo structure
*/
static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
if( ALWAYS(pWInfo) ){
whereClauseClear(&pWInfo->sWC);
while( pWInfo->pLoops ){
WhereLoop *p = pWInfo->pLoops;
pWInfo->pLoops = p->pNextLoop;
whereLoopDelete(db, p);
}
sqlite3DbFree(db, pWInfo);
}
}
/*
** Insert or replace a WhereLoop entry using the template supplied.
**
** An existing WhereLoop entry might be overwritten if the new template
** is better and has fewer dependencies. Or the template will be ignored
** and no insert will occur if an existing WhereLoop is faster and has
** fewer dependencies than the template. Otherwise a new WhereLoop is
** added based on the template.
**
** If pBuilder->pOrSet is not NULL then we only care about only the
** prerequisites and rRun and nOut costs of the N best loops. That
** information is gathered in the pBuilder->pOrSet object. This special
** processing mode is used only for OR clause processing.
**
** When accumulating multiple loops (when pBuilder->pOrSet is NULL) we
** still might overwrite similar loops with the new template if the
** template is better. Loops may be overwritten if the following
** conditions are met:
**
** (1) They have the same iTab.
** (2) They have the same iSortIdx.
** (3) The template has same or fewer dependencies than the current loop
** (4) The template has the same or lower cost than the current loop
** (5) The template uses more terms of the same index but has no additional
** dependencies
*/
static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
WhereLoop **ppPrev, *p, *pNext = 0;
WhereInfo *pWInfo = pBuilder->pWInfo;
sqlite3 *db = pWInfo->pParse->db;
/* If pBuilder->pOrSet is defined, then only keep track of the costs
** and prereqs.
*/
if( pBuilder->pOrSet!=0 ){
#if WHERETRACE_ENABLED
u16 n = pBuilder->pOrSet->n;
int x =
#endif
whereOrInsert(pBuilder->pOrSet, pTemplate->prereq, pTemplate->rRun,
pTemplate->nOut);
#if WHERETRACE_ENABLED
if( sqlite3WhereTrace & 0x8 ){
sqlite3DebugPrintf(x?" or-%d: ":" or-X: ", n);
whereLoopPrint(pTemplate, pWInfo->pTabList);
}
#endif
return SQLITE_OK;
}
/* Search for an existing WhereLoop to overwrite, or which takes
** priority over pTemplate.
*/
for(ppPrev=&pWInfo->pLoops, p=*ppPrev; p; ppPrev=&p->pNextLoop, p=*ppPrev){
if( p->iTab!=pTemplate->iTab || p->iSortIdx!=pTemplate->iSortIdx ){
/* If either the iTab or iSortIdx values for two WhereLoop are different
** then those WhereLoops need to be considered separately. Neither is
** a candidate to replace the other. */
continue;
}
/* In the current implementation, the rSetup value is either zero
** or the cost of building an automatic index (NlogN) and the NlogN
** is the same for compatible WhereLoops. */
assert( p->rSetup==0 || pTemplate->rSetup==0
|| p->rSetup==pTemplate->rSetup );
/* whereLoopAddBtree() always generates and inserts the automatic index
** case first. Hence compatible candidate WhereLoops never have a larger
** rSetup. Call this SETUP-INVARIANT */
assert( p->rSetup>=pTemplate->rSetup );
if( (p->prereq & pTemplate->prereq)==p->prereq
&& p->rSetup<=pTemplate->rSetup
&& p->rRun<=pTemplate->rRun
&& p->nOut<=pTemplate->nOut
){
/* This branch taken when p is equal or better than pTemplate in
** all of (1) dependencies (2) setup-cost, (3) run-cost, and
** (4) number of output rows. */
assert( p->rSetup==pTemplate->rSetup );
if( p->prereq==pTemplate->prereq
&& p->nLTerm<pTemplate->nLTerm
&& (p->wsFlags & pTemplate->wsFlags & WHERE_INDEXED)!=0
&& (p->u.btree.pIndex==pTemplate->u.btree.pIndex
|| pTemplate->rRun+p->nLTerm<=p->rRun+pTemplate->nLTerm)
){
/* Overwrite an existing WhereLoop with an similar one that uses
** more terms of the index */
pNext = p->pNextLoop;
break;
}else{
/* pTemplate is not helpful.
** Return without changing or adding anything */
goto whereLoopInsert_noop;
}
}
if( (p->prereq & pTemplate->prereq)==pTemplate->prereq
&& p->rRun>=pTemplate->rRun
&& p->nOut>=pTemplate->nOut
){
/* Overwrite an existing WhereLoop with a better one: one that is
** better at one of (1) dependencies, (2) setup-cost, (3) run-cost
** or (4) number of output rows, and is no worse in any of those
** categories. */
assert( p->rSetup>=pTemplate->rSetup ); /* SETUP-INVARIANT above */
pNext = p->pNextLoop;
break;
}
}
/* If we reach this point it means that either p[] should be overwritten
** with pTemplate[] if p[] exists, or if p==NULL then allocate a new
** WhereLoop and insert it.
*/
#if WHERETRACE_ENABLED
if( sqlite3WhereTrace & 0x8 ){
if( p!=0 ){
sqlite3DebugPrintf("ins-del: ");
whereLoopPrint(p, pWInfo->pTabList);
}
sqlite3DebugPrintf("ins-new: ");
whereLoopPrint(pTemplate, pWInfo->pTabList);
}
#endif
if( p==0 ){
p = sqlite3DbMallocRaw(db, sizeof(WhereLoop));
if( p==0 ) return SQLITE_NOMEM;
whereLoopInit(p);
}
whereLoopXfer(db, p, pTemplate);
p->pNextLoop = pNext;
*ppPrev = p;
if( (p->wsFlags & WHERE_VIRTUALTABLE)==0 ){
Index *pIndex = p->u.btree.pIndex;
if( pIndex && pIndex->tnum==0 ){
p->u.btree.pIndex = 0;
}
}
return SQLITE_OK;
/* Jump here if the insert is a no-op */
whereLoopInsert_noop:
#if WHERETRACE_ENABLED
if( sqlite3WhereTrace & 0x8 ){
sqlite3DebugPrintf("ins-noop: ");
whereLoopPrint(pTemplate, pWInfo->pTabList);
}
#endif
return SQLITE_OK;
}
/*
** Adjust the WhereLoop.nOut value downward to account for terms of the
** WHERE clause that reference the loop but which are not used by an
** index.
**
** In the current implementation, the first extra WHERE clause term reduces
** the number of output rows by a factor of 10 and each additional term
** reduces the number of output rows by sqrt(2).
*/
static void whereLoopOutputAdjust(WhereClause *pWC, WhereLoop *pLoop){
WhereTerm *pTerm, *pX;
Bitmask notAllowed = ~(pLoop->prereq|pLoop->maskSelf);
int i, j;
if( !OptimizationEnabled(pWC->pWInfo->pParse->db, SQLITE_AdjustOutEst) ){
return;
}
for(i=pWC->nTerm, pTerm=pWC->a; i>0; i--, pTerm++){
if( (pTerm->wtFlags & TERM_VIRTUAL)!=0 ) break;
if( (pTerm->prereqAll & pLoop->maskSelf)==0 ) continue;
if( (pTerm->prereqAll & notAllowed)!=0 ) continue;
for(j=pLoop->nLTerm-1; j>=0; j--){
pX = pLoop->aLTerm[j];
if( pX==pTerm ) break;
if( pX->iParent>=0 && (&pWC->a[pX->iParent])==pTerm ) break;
}
if( j<0 ) pLoop->nOut += pTerm->truthProb;
}
}
/*
** We have so far matched pBuilder->pNew->u.btree.nEq terms of the index pIndex.
** Try to match one more.
**
** If pProbe->tnum==0, that means pIndex is a fake index used for the
** INTEGER PRIMARY KEY.
*/
static int whereLoopAddBtreeIndex(
WhereLoopBuilder *pBuilder, /* The WhereLoop factory */
struct SrcList_item *pSrc, /* FROM clause term being analyzed */
Index *pProbe, /* An index on pSrc */
LogEst nInMul /* log(Number of iterations due to IN) */
){
WhereInfo *pWInfo = pBuilder->pWInfo; /* WHERE analyse context */
Parse *pParse = pWInfo->pParse; /* Parsing context */
sqlite3 *db = pParse->db; /* Database connection malloc context */
WhereLoop *pNew; /* Template WhereLoop under construction */
WhereTerm *pTerm; /* A WhereTerm under consideration */
int opMask; /* Valid operators for constraints */
WhereScan scan; /* Iterator for WHERE terms */
Bitmask saved_prereq; /* Original value of pNew->prereq */
u16 saved_nLTerm; /* Original value of pNew->nLTerm */
int saved_nEq; /* Original value of pNew->u.btree.nEq */
u32 saved_wsFlags; /* Original value of pNew->wsFlags */
LogEst saved_nOut; /* Original value of pNew->nOut */
int iCol; /* Index of the column in the table */
int rc = SQLITE_OK; /* Return code */
LogEst nRowEst; /* Estimated index selectivity */
LogEst rLogSize; /* Logarithm of table size */
WhereTerm *pTop = 0, *pBtm = 0; /* Top and bottom range constraints */
pNew = pBuilder->pNew;
if( db->mallocFailed ) return SQLITE_NOMEM;
assert( (pNew->wsFlags & WHERE_VIRTUALTABLE)==0 );
assert( (pNew->wsFlags & WHERE_TOP_LIMIT)==0 );
if( pNew->wsFlags & WHERE_BTM_LIMIT ){
opMask = WO_LT|WO_LE;
}else if( pProbe->tnum<=0 || (pSrc->jointype & JT_LEFT)!=0 ){
opMask = WO_EQ|WO_IN|WO_GT|WO_GE|WO_LT|WO_LE;
}else{
opMask = WO_EQ|WO_IN|WO_ISNULL|WO_GT|WO_GE|WO_LT|WO_LE;
}
if( pProbe->bUnordered ) opMask &= ~(WO_GT|WO_GE|WO_LT|WO_LE);
assert( pNew->u.btree.nEq<=pProbe->nColumn );
if( pNew->u.btree.nEq < pProbe->nColumn ){
iCol = pProbe->aiColumn[pNew->u.btree.nEq];
nRowEst = sqlite3LogEst(pProbe->aiRowEst[pNew->u.btree.nEq+1]);
if( nRowEst==0 && pProbe->onError==OE_None ) nRowEst = 1;
}else{
iCol = -1;
nRowEst = 0;
}
pTerm = whereScanInit(&scan, pBuilder->pWC, pSrc->iCursor, iCol,
opMask, pProbe);
saved_nEq = pNew->u.btree.nEq;
saved_nLTerm = pNew->nLTerm;
saved_wsFlags = pNew->wsFlags;
saved_prereq = pNew->prereq;
saved_nOut = pNew->nOut;
pNew->rSetup = 0;
rLogSize = estLog(sqlite3LogEst(pProbe->aiRowEst[0]));
for(; rc==SQLITE_OK && pTerm!=0; pTerm = whereScanNext(&scan)){
int nIn = 0;
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
int nRecValid = pBuilder->nRecValid;
#endif
if( (pTerm->eOperator==WO_ISNULL || (pTerm->wtFlags&TERM_VNULL)!=0)
&& (iCol<0 || pSrc->pTab->aCol[iCol].notNull)
){
continue; /* ignore IS [NOT] NULL constraints on NOT NULL columns */
}
if( pTerm->prereqRight & pNew->maskSelf ) continue;
assert( pNew->nOut==saved_nOut );
pNew->wsFlags = saved_wsFlags;
pNew->u.btree.nEq = saved_nEq;
pNew->nLTerm = saved_nLTerm;
if( whereLoopResize(db, pNew, pNew->nLTerm+1) ) break; /* OOM */
pNew->aLTerm[pNew->nLTerm++] = pTerm;
pNew->prereq = (saved_prereq | pTerm->prereqRight) & ~pNew->maskSelf;
pNew->rRun = rLogSize; /* Baseline cost is log2(N). Adjustments below */
if( pTerm->eOperator & WO_IN ){
Expr *pExpr = pTerm->pExpr;
pNew->wsFlags |= WHERE_COLUMN_IN;
if( ExprHasProperty(pExpr, EP_xIsSelect) ){
/* "x IN (SELECT ...)": TUNING: the SELECT returns 25 rows */
nIn = 46; assert( 46==sqlite3LogEst(25) );
}else if( ALWAYS(pExpr->x.pList && pExpr->x.pList->nExpr) ){
/* "x IN (value, value, ...)" */
nIn = sqlite3LogEst(pExpr->x.pList->nExpr);
}
pNew->rRun += nIn;
pNew->u.btree.nEq++;
pNew->nOut = nRowEst + nInMul + nIn;
}else if( pTerm->eOperator & (WO_EQ) ){
assert( (pNew->wsFlags & (WHERE_COLUMN_NULL|WHERE_COLUMN_IN))!=0
|| nInMul==0 );
pNew->wsFlags |= WHERE_COLUMN_EQ;
if( iCol<0
|| (pProbe->onError!=OE_None && nInMul==0
&& pNew->u.btree.nEq==pProbe->nColumn-1)
){
assert( (pNew->wsFlags & WHERE_COLUMN_IN)==0 || iCol<0 );
pNew->wsFlags |= WHERE_ONEROW;
}
pNew->u.btree.nEq++;
pNew->nOut = nRowEst + nInMul;
}else if( pTerm->eOperator & (WO_ISNULL) ){
pNew->wsFlags |= WHERE_COLUMN_NULL;
pNew->u.btree.nEq++;
/* TUNING: IS NULL selects 2 rows */
nIn = 10; assert( 10==sqlite3LogEst(2) );
pNew->nOut = nRowEst + nInMul + nIn;
}else if( pTerm->eOperator & (WO_GT|WO_GE) ){
testcase( pTerm->eOperator & WO_GT );
testcase( pTerm->eOperator & WO_GE );
pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_BTM_LIMIT;
pBtm = pTerm;
pTop = 0;
}else{
assert( pTerm->eOperator & (WO_LT|WO_LE) );
testcase( pTerm->eOperator & WO_LT );
testcase( pTerm->eOperator & WO_LE );
pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_TOP_LIMIT;
pTop = pTerm;
pBtm = (pNew->wsFlags & WHERE_BTM_LIMIT)!=0 ?
pNew->aLTerm[pNew->nLTerm-2] : 0;
}
if( pNew->wsFlags & WHERE_COLUMN_RANGE ){
/* Adjust nOut and rRun for STAT3 range values */
assert( pNew->nOut==saved_nOut );
whereRangeScanEst(pParse, pBuilder, pBtm, pTop, pNew);
}
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
if( nInMul==0
&& pProbe->nSample
&& pNew->u.btree.nEq<=pProbe->nSampleCol
&& OptimizationEnabled(db, SQLITE_Stat3)
){
Expr *pExpr = pTerm->pExpr;
tRowcnt nOut = 0;
if( (pTerm->eOperator & (WO_EQ|WO_ISNULL))!=0 ){
testcase( pTerm->eOperator & WO_EQ );
testcase( pTerm->eOperator & WO_ISNULL );
rc = whereEqualScanEst(pParse, pBuilder, pExpr->pRight, &nOut);
}else if( (pTerm->eOperator & WO_IN)
&& !ExprHasProperty(pExpr, EP_xIsSelect) ){
rc = whereInScanEst(pParse, pBuilder, pExpr->x.pList, &nOut);
}
assert( nOut==0 || rc==SQLITE_OK );
if( nOut ){
pNew->nOut = sqlite3LogEst(nOut);
if( pNew->nOut>saved_nOut ) pNew->nOut = saved_nOut;
}
}
#endif
if( (pNew->wsFlags & (WHERE_IDX_ONLY|WHERE_IPK))==0 ){
/* Each row involves a step of the index, then a binary search of
** the main table */
pNew->rRun = sqlite3LogEstAdd(pNew->rRun,rLogSize>27 ? rLogSize-17 : 10);
}
/* Step cost for each output row */
pNew->rRun = sqlite3LogEstAdd(pNew->rRun, pNew->nOut);
whereLoopOutputAdjust(pBuilder->pWC, pNew);
rc = whereLoopInsert(pBuilder, pNew);
if( (pNew->wsFlags & WHERE_TOP_LIMIT)==0
&& pNew->u.btree.nEq<(pProbe->nColumn + (pProbe->zName!=0))
){
whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, nInMul+nIn);
}
pNew->nOut = saved_nOut;
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
pBuilder->nRecValid = nRecValid;
#endif
}
pNew->prereq = saved_prereq;
pNew->u.btree.nEq = saved_nEq;
pNew->wsFlags = saved_wsFlags;
pNew->nOut = saved_nOut;
pNew->nLTerm = saved_nLTerm;
return rc;
}
/*
** Return True if it is possible that pIndex might be useful in
** implementing the ORDER BY clause in pBuilder.
**
** Return False if pBuilder does not contain an ORDER BY clause or
** if there is no way for pIndex to be useful in implementing that
** ORDER BY clause.
*/
static int indexMightHelpWithOrderBy(
WhereLoopBuilder *pBuilder,
Index *pIndex,
int iCursor
){
ExprList *pOB;
int ii, jj;
if( pIndex->bUnordered ) return 0;
if( (pOB = pBuilder->pWInfo->pOrderBy)==0 ) return 0;
for(ii=0; ii<pOB->nExpr; ii++){
Expr *pExpr = sqlite3ExprSkipCollate(pOB->a[ii].pExpr);
if( pExpr->op!=TK_COLUMN ) return 0;
if( pExpr->iTable==iCursor ){
for(jj=0; jj<pIndex->nColumn; jj++){
if( pExpr->iColumn==pIndex->aiColumn[jj] ) return 1;
}
}
}
return 0;
}
/*
** Return a bitmask where 1s indicate that the corresponding column of
** the table is used by an index. Only the first 63 columns are considered.
*/
static Bitmask columnsInIndex(Index *pIdx){
Bitmask m = 0;
int j;
for(j=pIdx->nColumn-1; j>=0; j--){
int x = pIdx->aiColumn[j];
assert( x>=0 );
testcase( x==BMS-1 );
testcase( x==BMS-2 );
if( x<BMS-1 ) m |= MASKBIT(x);
}
return m;
}
/* Check to see if a partial index with pPartIndexWhere can be used
** in the current query. Return true if it can be and false if not.
*/
static int whereUsablePartialIndex(int iTab, WhereClause *pWC, Expr *pWhere){
int i;
WhereTerm *pTerm;
for(i=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
if( sqlite3ExprImpliesExpr(pTerm->pExpr, pWhere, iTab) ) return 1;
}
return 0;
}
/*
** Add all WhereLoop objects for a single table of the join where the table
** is idenfied by pBuilder->pNew->iTab. That table is guaranteed to be
** a b-tree table, not a virtual table.
*/
static int whereLoopAddBtree(
WhereLoopBuilder *pBuilder, /* WHERE clause information */
Bitmask mExtra /* Extra prerequesites for using this table */
){
WhereInfo *pWInfo; /* WHERE analysis context */
Index *pProbe; /* An index we are evaluating */
Index sPk; /* A fake index object for the primary key */
tRowcnt aiRowEstPk[2]; /* The aiRowEst[] value for the sPk index */
int aiColumnPk = -1; /* The aColumn[] value for the sPk index */
SrcList *pTabList; /* The FROM clause */
struct SrcList_item *pSrc; /* The FROM clause btree term to add */
WhereLoop *pNew; /* Template WhereLoop object */
int rc = SQLITE_OK; /* Return code */
int iSortIdx = 1; /* Index number */
int b; /* A boolean value */
LogEst rSize; /* number of rows in the table */
LogEst rLogSize; /* Logarithm of the number of rows in the table */
WhereClause *pWC; /* The parsed WHERE clause */
Table *pTab; /* Table being queried */
pNew = pBuilder->pNew;
pWInfo = pBuilder->pWInfo;
pTabList = pWInfo->pTabList;
pSrc = pTabList->a + pNew->iTab;
pTab = pSrc->pTab;
pWC = pBuilder->pWC;
assert( !IsVirtual(pSrc->pTab) );
if( pSrc->pIndex ){
/* An INDEXED BY clause specifies a particular index to use */
pProbe = pSrc->pIndex;
}else{
/* There is no INDEXED BY clause. Create a fake Index object in local
** variable sPk to represent the rowid primary key index. Make this
** fake index the first in a chain of Index objects with all of the real
** indices to follow */
Index *pFirst; /* First of real indices on the table */
memset(&sPk, 0, sizeof(Index));
sPk.nColumn = 1;
sPk.aiColumn = &aiColumnPk;
sPk.aiRowEst = aiRowEstPk;
sPk.onError = OE_Replace;
sPk.pTable = pTab;
aiRowEstPk[0] = pTab->nRowEst;
aiRowEstPk[1] = 1;
pFirst = pSrc->pTab->pIndex;
if( pSrc->notIndexed==0 ){
/* The real indices of the table are only considered if the
** NOT INDEXED qualifier is omitted from the FROM clause */
sPk.pNext = pFirst;
}
pProbe = &sPk;
}
rSize = sqlite3LogEst(pTab->nRowEst);
rLogSize = estLog(rSize);
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
/* Automatic indexes */
if( !pBuilder->pOrSet
&& (pWInfo->pParse->db->flags & SQLITE_AutoIndex)!=0
&& pSrc->pIndex==0
&& !pSrc->viaCoroutine
&& !pSrc->notIndexed
&& !pSrc->isCorrelated
){
/* Generate auto-index WhereLoops */
WhereTerm *pTerm;
WhereTerm *pWCEnd = pWC->a + pWC->nTerm;
for(pTerm=pWC->a; rc==SQLITE_OK && pTerm<pWCEnd; pTerm++){
if( pTerm->prereqRight & pNew->maskSelf ) continue;
if( termCanDriveIndex(pTerm, pSrc, 0) ){
pNew->u.btree.nEq = 1;
pNew->u.btree.pIndex = 0;
pNew->nLTerm = 1;
pNew->aLTerm[0] = pTerm;
/* TUNING: One-time cost for computing the automatic index is
** approximately 7*N*log2(N) where N is the number of rows in
** the table being indexed. */
pNew->rSetup = rLogSize + rSize + 28; assert( 28==sqlite3LogEst(7) );
/* TUNING: Each index lookup yields 20 rows in the table. This
** is more than the usual guess of 10 rows, since we have no way
** of knowning how selective the index will ultimately be. It would
** not be unreasonable to make this value much larger. */
pNew->nOut = 43; assert( 43==sqlite3LogEst(20) );
pNew->rRun = sqlite3LogEstAdd(rLogSize,pNew->nOut);
pNew->wsFlags = WHERE_AUTO_INDEX;
pNew->prereq = mExtra | pTerm->prereqRight;
rc = whereLoopInsert(pBuilder, pNew);
}
}
}
#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
/* Loop over all indices
*/
for(; rc==SQLITE_OK && pProbe; pProbe=pProbe->pNext, iSortIdx++){
if( pProbe->pPartIdxWhere!=0
&& !whereUsablePartialIndex(pNew->iTab, pWC, pProbe->pPartIdxWhere) ){
continue; /* Partial index inappropriate for this query */
}
pNew->u.btree.nEq = 0;
pNew->nLTerm = 0;
pNew->iSortIdx = 0;
pNew->rSetup = 0;
pNew->prereq = mExtra;
pNew->nOut = rSize;
pNew->u.btree.pIndex = pProbe;
b = indexMightHelpWithOrderBy(pBuilder, pProbe, pSrc->iCursor);
/* The ONEPASS_DESIRED flags never occurs together with ORDER BY */
assert( (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || b==0 );
if( pProbe->tnum<=0 ){
/* Integer primary key index */
pNew->wsFlags = WHERE_IPK;
/* Full table scan */
pNew->iSortIdx = b ? iSortIdx : 0;
/* TUNING: Cost of full table scan is 3*(N + log2(N)).
** + The extra 3 factor is to encourage the use of indexed lookups
** over full scans. FIXME */
pNew->rRun = sqlite3LogEstAdd(rSize,rLogSize) + 16;
whereLoopOutputAdjust(pWC, pNew);
rc = whereLoopInsert(pBuilder, pNew);
pNew->nOut = rSize;
if( rc ) break;
}else{
Bitmask m = pSrc->colUsed & ~columnsInIndex(pProbe);
pNew->wsFlags = (m==0) ? (WHERE_IDX_ONLY|WHERE_INDEXED) : WHERE_INDEXED;
/* Full scan via index */
if( b
|| ( m==0
&& pProbe->bUnordered==0
&& pProbe->szIdxRow<pTab->szTabRow
&& (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0
&& sqlite3GlobalConfig.bUseCis
&& OptimizationEnabled(pWInfo->pParse->db, SQLITE_CoverIdxScan)
)
){
pNew->iSortIdx = b ? iSortIdx : 0;
if( m==0 ){
/* TUNING: Cost of a covering index scan is K*(N + log2(N)).
** + The extra factor K of between 1.1 and 3.0 that depends
** on the relative sizes of the table and the index. K
** is smaller for smaller indices, thus favoring them.
*/
pNew->rRun = sqlite3LogEstAdd(rSize,rLogSize) + 1 +
(15*pProbe->szIdxRow)/pTab->szTabRow;
}else{
assert( b!=0 );
/* TUNING: Cost of scanning a non-covering index is (N+1)*log2(N)
** which we will simplify to just N*log2(N) */
pNew->rRun = rSize + rLogSize;
}
whereLoopOutputAdjust(pWC, pNew);
rc = whereLoopInsert(pBuilder, pNew);
pNew->nOut = rSize;
if( rc ) break;
}
}
rc = whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, 0);
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
sqlite3Stat4ProbeFree(pBuilder->pRec);
pBuilder->nRecValid = 0;
pBuilder->pRec = 0;
#endif
/* If there was an INDEXED BY clause, then only that one index is
** considered. */
if( pSrc->pIndex ) break;
}
return rc;
}
#ifndef SQLITE_OMIT_VIRTUALTABLE
/*
** Add all WhereLoop objects for a table of the join identified by
** pBuilder->pNew->iTab. That table is guaranteed to be a virtual table.
*/
static int whereLoopAddVirtual(
WhereLoopBuilder *pBuilder /* WHERE clause information */
){
WhereInfo *pWInfo; /* WHERE analysis context */
Parse *pParse; /* The parsing context */
WhereClause *pWC; /* The WHERE clause */
struct SrcList_item *pSrc; /* The FROM clause term to search */
Table *pTab;
sqlite3 *db;
sqlite3_index_info *pIdxInfo;
struct sqlite3_index_constraint *pIdxCons;
struct sqlite3_index_constraint_usage *pUsage;
WhereTerm *pTerm;
int i, j;
int iTerm, mxTerm;
int nConstraint;
int seenIn = 0; /* True if an IN operator is seen */
int seenVar = 0; /* True if a non-constant constraint is seen */
int iPhase; /* 0: const w/o IN, 1: const, 2: no IN, 2: IN */
WhereLoop *pNew;
int rc = SQLITE_OK;
pWInfo = pBuilder->pWInfo;
pParse = pWInfo->pParse;
db = pParse->db;
pWC = pBuilder->pWC;
pNew = pBuilder->pNew;
pSrc = &pWInfo->pTabList->a[pNew->iTab];
pTab = pSrc->pTab;
assert( IsVirtual(pTab) );
pIdxInfo = allocateIndexInfo(pParse, pWC, pSrc, pBuilder->pOrderBy);
if( pIdxInfo==0 ) return SQLITE_NOMEM;
pNew->prereq = 0;
pNew->rSetup = 0;
pNew->wsFlags = WHERE_VIRTUALTABLE;
pNew->nLTerm = 0;
pNew->u.vtab.needFree = 0;
pUsage = pIdxInfo->aConstraintUsage;
nConstraint = pIdxInfo->nConstraint;
if( whereLoopResize(db, pNew, nConstraint) ){
sqlite3DbFree(db, pIdxInfo);
return SQLITE_NOMEM;
}
for(iPhase=0; iPhase<=3; iPhase++){
if( !seenIn && (iPhase&1)!=0 ){
iPhase++;
if( iPhase>3 ) break;
}
if( !seenVar && iPhase>1 ) break;
pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
j = pIdxCons->iTermOffset;
pTerm = &pWC->a[j];
switch( iPhase ){
case 0: /* Constants without IN operator */
pIdxCons->usable = 0;
if( (pTerm->eOperator & WO_IN)!=0 ){
seenIn = 1;
}
if( pTerm->prereqRight!=0 ){
seenVar = 1;
}else if( (pTerm->eOperator & WO_IN)==0 ){
pIdxCons->usable = 1;
}
break;
case 1: /* Constants with IN operators */
assert( seenIn );
pIdxCons->usable = (pTerm->prereqRight==0);
break;
case 2: /* Variables without IN */
assert( seenVar );
pIdxCons->usable = (pTerm->eOperator & WO_IN)==0;
break;
default: /* Variables with IN */
assert( seenVar && seenIn );
pIdxCons->usable = 1;
break;
}
}
memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
if( pIdxInfo->needToFreeIdxStr ) sqlite3_free(pIdxInfo->idxStr);
pIdxInfo->idxStr = 0;
pIdxInfo->idxNum = 0;
pIdxInfo->needToFreeIdxStr = 0;
pIdxInfo->orderByConsumed = 0;
pIdxInfo->estimatedCost = SQLITE_BIG_DBL / (double)2;
rc = vtabBestIndex(pParse, pTab, pIdxInfo);
if( rc ) goto whereLoopAddVtab_exit;
pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
pNew->prereq = 0;
mxTerm = -1;
assert( pNew->nLSlot>=nConstraint );
for(i=0; i<nConstraint; i++) pNew->aLTerm[i] = 0;
pNew->u.vtab.omitMask = 0;
for(i=0; i<nConstraint; i++, pIdxCons++){
if( (iTerm = pUsage[i].argvIndex - 1)>=0 ){
j = pIdxCons->iTermOffset;
if( iTerm>=nConstraint
|| j<0
|| j>=pWC->nTerm
|| pNew->aLTerm[iTerm]!=0
){
rc = SQLITE_ERROR;
sqlite3ErrorMsg(pParse, "%s.xBestIndex() malfunction", pTab->zName);
goto whereLoopAddVtab_exit;
}
testcase( iTerm==nConstraint-1 );
testcase( j==0 );
testcase( j==pWC->nTerm-1 );
pTerm = &pWC->a[j];
pNew->prereq |= pTerm->prereqRight;
assert( iTerm<pNew->nLSlot );
pNew->aLTerm[iTerm] = pTerm;
if( iTerm>mxTerm ) mxTerm = iTerm;
testcase( iTerm==15 );
testcase( iTerm==16 );
if( iTerm<16 && pUsage[i].omit ) pNew->u.vtab.omitMask |= 1<<iTerm;
if( (pTerm->eOperator & WO_IN)!=0 ){
if( pUsage[i].omit==0 ){
/* Do not attempt to use an IN constraint if the virtual table
** says that the equivalent EQ constraint cannot be safely omitted.
** If we do attempt to use such a constraint, some rows might be
** repeated in the output. */
break;
}
/* A virtual table that is constrained by an IN clause may not
** consume the ORDER BY clause because (1) the order of IN terms
** is not necessarily related to the order of output terms and
** (2) Multiple outputs from a single IN value will not merge
** together. */
pIdxInfo->orderByConsumed = 0;
}
}
}
if( i>=nConstraint ){
pNew->nLTerm = mxTerm+1;
assert( pNew->nLTerm<=pNew->nLSlot );
pNew->u.vtab.idxNum = pIdxInfo->idxNum;
pNew->u.vtab.needFree = pIdxInfo->needToFreeIdxStr;
pIdxInfo->needToFreeIdxStr = 0;
pNew->u.vtab.idxStr = pIdxInfo->idxStr;
pNew->u.vtab.isOrdered = (u8)((pIdxInfo->nOrderBy!=0)
&& pIdxInfo->orderByConsumed);
pNew->rSetup = 0;
pNew->rRun = sqlite3LogEstFromDouble(pIdxInfo->estimatedCost);
/* TUNING: Every virtual table query returns 25 rows */
pNew->nOut = 46; assert( 46==sqlite3LogEst(25) );
whereLoopInsert(pBuilder, pNew);
if( pNew->u.vtab.needFree ){
sqlite3_free(pNew->u.vtab.idxStr);
pNew->u.vtab.needFree = 0;
}
}
}
whereLoopAddVtab_exit:
if( pIdxInfo->needToFreeIdxStr ) sqlite3_free(pIdxInfo->idxStr);
sqlite3DbFree(db, pIdxInfo);
return rc;
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */
/*
** Add WhereLoop entries to handle OR terms. This works for either
** btrees or virtual tables.
*/
static int whereLoopAddOr(WhereLoopBuilder *pBuilder, Bitmask mExtra){
WhereInfo *pWInfo = pBuilder->pWInfo;
WhereClause *pWC;
WhereLoop *pNew;
WhereTerm *pTerm, *pWCEnd;
int rc = SQLITE_OK;
int iCur;
WhereClause tempWC;
WhereLoopBuilder sSubBuild;
WhereOrSet sSum, sCur, sPrev;
struct SrcList_item *pItem;
pWC = pBuilder->pWC;
if( pWInfo->wctrlFlags & WHERE_AND_ONLY ) return SQLITE_OK;
pWCEnd = pWC->a + pWC->nTerm;
pNew = pBuilder->pNew;
memset(&sSum, 0, sizeof(sSum));
pItem = pWInfo->pTabList->a + pNew->iTab;
iCur = pItem->iCursor;
for(pTerm=pWC->a; pTerm<pWCEnd && rc==SQLITE_OK; pTerm++){
if( (pTerm->eOperator & WO_OR)!=0
&& (pTerm->u.pOrInfo->indexable & pNew->maskSelf)!=0
){
WhereClause * const pOrWC = &pTerm->u.pOrInfo->wc;
WhereTerm * const pOrWCEnd = &pOrWC->a[pOrWC->nTerm];
WhereTerm *pOrTerm;
int once = 1;
int i, j;
sSubBuild = *pBuilder;
sSubBuild.pOrderBy = 0;
sSubBuild.pOrSet = &sCur;
for(pOrTerm=pOrWC->a; pOrTerm<pOrWCEnd; pOrTerm++){
if( (pOrTerm->eOperator & WO_AND)!=0 ){
sSubBuild.pWC = &pOrTerm->u.pAndInfo->wc;
}else if( pOrTerm->leftCursor==iCur ){
tempWC.pWInfo = pWC->pWInfo;
tempWC.pOuter = pWC;
tempWC.op = TK_AND;
tempWC.nTerm = 1;
tempWC.a = pOrTerm;
sSubBuild.pWC = &tempWC;
}else{
continue;
}
sCur.n = 0;
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( IsVirtual(pItem->pTab) ){
rc = whereLoopAddVirtual(&sSubBuild);
for(i=0; i<sCur.n; i++) sCur.a[i].prereq |= mExtra;
}else
#endif
{
rc = whereLoopAddBtree(&sSubBuild, mExtra);
}
assert( rc==SQLITE_OK || sCur.n==0 );
if( sCur.n==0 ){
sSum.n = 0;
break;
}else if( once ){
whereOrMove(&sSum, &sCur);
once = 0;
}else{
whereOrMove(&sPrev, &sSum);
sSum.n = 0;
for(i=0; i<sPrev.n; i++){
for(j=0; j<sCur.n; j++){
whereOrInsert(&sSum, sPrev.a[i].prereq | sCur.a[j].prereq,
sqlite3LogEstAdd(sPrev.a[i].rRun, sCur.a[j].rRun),
sqlite3LogEstAdd(sPrev.a[i].nOut, sCur.a[j].nOut));
}
}
}
}
pNew->nLTerm = 1;
pNew->aLTerm[0] = pTerm;
pNew->wsFlags = WHERE_MULTI_OR;
pNew->rSetup = 0;
pNew->iSortIdx = 0;
memset(&pNew->u, 0, sizeof(pNew->u));
for(i=0; rc==SQLITE_OK && i<sSum.n; i++){
/* TUNING: Multiple by 3.5 for the secondary table lookup */
pNew->rRun = sSum.a[i].rRun + 18;
pNew->nOut = sSum.a[i].nOut;
pNew->prereq = sSum.a[i].prereq;
rc = whereLoopInsert(pBuilder, pNew);
}
}
}
return rc;
}
/*
** Add all WhereLoop objects for all tables
*/
static int whereLoopAddAll(WhereLoopBuilder *pBuilder){
WhereInfo *pWInfo = pBuilder->pWInfo;
Bitmask mExtra = 0;
Bitmask mPrior = 0;
int iTab;
SrcList *pTabList = pWInfo->pTabList;
struct SrcList_item *pItem;
sqlite3 *db = pWInfo->pParse->db;
int nTabList = pWInfo->nLevel;
int rc = SQLITE_OK;
u8 priorJoinType = 0;
WhereLoop *pNew;
/* Loop over the tables in the join, from left to right */
pNew = pBuilder->pNew;
whereLoopInit(pNew);
for(iTab=0, pItem=pTabList->a; iTab<nTabList; iTab++, pItem++){
pNew->iTab = iTab;
pNew->maskSelf = getMask(&pWInfo->sMaskSet, pItem->iCursor);
if( ((pItem->jointype|priorJoinType) & (JT_LEFT|JT_CROSS))!=0 ){
mExtra = mPrior;
}
priorJoinType = pItem->jointype;
if( IsVirtual(pItem->pTab) ){
rc = whereLoopAddVirtual(pBuilder);
}else{
rc = whereLoopAddBtree(pBuilder, mExtra);
}
if( rc==SQLITE_OK ){
rc = whereLoopAddOr(pBuilder, mExtra);
}
mPrior |= pNew->maskSelf;
if( rc || db->mallocFailed ) break;
}
whereLoopClear(db, pNew);
return rc;
}
/*
** Examine a WherePath (with the addition of the extra WhereLoop of the 5th
** parameters) to see if it outputs rows in the requested ORDER BY
** (or GROUP BY) without requiring a separate sort operation. Return:
**
** 0: ORDER BY is not satisfied. Sorting required
** 1: ORDER BY is satisfied. Omit sorting
** -1: Unknown at this time
**
** Note that processing for WHERE_GROUPBY and WHERE_DISTINCTBY is not as
** strict. With GROUP BY and DISTINCT the only requirement is that
** equivalent rows appear immediately adjacent to one another. GROUP BY
** and DISTINT do not require rows to appear in any particular order as long
** as equivelent rows are grouped together. Thus for GROUP BY and DISTINCT
** the pOrderBy terms can be matched in any order. With ORDER BY, the
** pOrderBy terms must be matched in strict left-to-right order.
*/
static int wherePathSatisfiesOrderBy(
WhereInfo *pWInfo, /* The WHERE clause */
ExprList *pOrderBy, /* ORDER BY or GROUP BY or DISTINCT clause to check */
WherePath *pPath, /* The WherePath to check */
u16 wctrlFlags, /* Might contain WHERE_GROUPBY or WHERE_DISTINCTBY */
u16 nLoop, /* Number of entries in pPath->aLoop[] */
WhereLoop *pLast, /* Add this WhereLoop to the end of pPath->aLoop[] */
Bitmask *pRevMask /* OUT: Mask of WhereLoops to run in reverse order */
){
u8 revSet; /* True if rev is known */
u8 rev; /* Composite sort order */
u8 revIdx; /* Index sort order */
u8 isOrderDistinct; /* All prior WhereLoops are order-distinct */
u8 distinctColumns; /* True if the loop has UNIQUE NOT NULL columns */
u8 isMatch; /* iColumn matches a term of the ORDER BY clause */
u16 nColumn; /* Number of columns in pIndex */
u16 nOrderBy; /* Number terms in the ORDER BY clause */
int iLoop; /* Index of WhereLoop in pPath being processed */
int i, j; /* Loop counters */
int iCur; /* Cursor number for current WhereLoop */
int iColumn; /* A column number within table iCur */
WhereLoop *pLoop = 0; /* Current WhereLoop being processed. */
WhereTerm *pTerm; /* A single term of the WHERE clause */
Expr *pOBExpr; /* An expression from the ORDER BY clause */
CollSeq *pColl; /* COLLATE function from an ORDER BY clause term */
Index *pIndex; /* The index associated with pLoop */
sqlite3 *db = pWInfo->pParse->db; /* Database connection */
Bitmask obSat = 0; /* Mask of ORDER BY terms satisfied so far */
Bitmask obDone; /* Mask of all ORDER BY terms */
Bitmask orderDistinctMask; /* Mask of all well-ordered loops */
Bitmask ready; /* Mask of inner loops */
/*
** We say the WhereLoop is "one-row" if it generates no more than one
** row of output. A WhereLoop is one-row if all of the following are true:
** (a) All index columns match with WHERE_COLUMN_EQ.
** (b) The index is unique
** Any WhereLoop with an WHERE_COLUMN_EQ constraint on the rowid is one-row.
** Every one-row WhereLoop will have the WHERE_ONEROW bit set in wsFlags.
**
** We say the WhereLoop is "order-distinct" if the set of columns from
** that WhereLoop that are in the ORDER BY clause are different for every
** row of the WhereLoop. Every one-row WhereLoop is automatically
** order-distinct. A WhereLoop that has no columns in the ORDER BY clause
** is not order-distinct. To be order-distinct is not quite the same as being
** UNIQUE since a UNIQUE column or index can have multiple rows that
** are NULL and NULL values are equivalent for the purpose of order-distinct.
** To be order-distinct, the columns must be UNIQUE and NOT NULL.
**
** The rowid for a table is always UNIQUE and NOT NULL so whenever the
** rowid appears in the ORDER BY clause, the corresponding WhereLoop is
** automatically order-distinct.
*/
assert( pOrderBy!=0 );
/* Sortability of virtual tables is determined by the xBestIndex method
** of the virtual table itself */
if( pLast->wsFlags & WHERE_VIRTUALTABLE ){
testcase( nLoop>0 ); /* True when outer loops are one-row and match
** no ORDER BY terms */
return pLast->u.vtab.isOrdered;
}
if( nLoop && OptimizationDisabled(db, SQLITE_OrderByIdxJoin) ) return 0;
nOrderBy = pOrderBy->nExpr;
testcase( nOrderBy==BMS-1 );
if( nOrderBy>BMS-1 ) return 0; /* Cannot optimize overly large ORDER BYs */
isOrderDistinct = 1;
obDone = MASKBIT(nOrderBy)-1;
orderDistinctMask = 0;
ready = 0;
for(iLoop=0; isOrderDistinct && obSat<obDone && iLoop<=nLoop; iLoop++){
if( iLoop>0 ) ready |= pLoop->maskSelf;
pLoop = iLoop<nLoop ? pPath->aLoop[iLoop] : pLast;
assert( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0 );
iCur = pWInfo->pTabList->a[pLoop->iTab].iCursor;
/* Mark off any ORDER BY term X that is a column in the table of
** the current loop for which there is term in the WHERE
** clause of the form X IS NULL or X=? that reference only outer
** loops.
*/
for(i=0; i<nOrderBy; i++){
if( MASKBIT(i) & obSat ) continue;
pOBExpr = sqlite3ExprSkipCollate(pOrderBy->a[i].pExpr);
if( pOBExpr->op!=TK_COLUMN ) continue;
if( pOBExpr->iTable!=iCur ) continue;
pTerm = findTerm(&pWInfo->sWC, iCur, pOBExpr->iColumn,
~ready, WO_EQ|WO_ISNULL, 0);
if( pTerm==0 ) continue;
if( (pTerm->eOperator&WO_EQ)!=0 && pOBExpr->iColumn>=0 ){
const char *z1, *z2;
pColl = sqlite3ExprCollSeq(pWInfo->pParse, pOrderBy->a[i].pExpr);
if( !pColl ) pColl = db->pDfltColl;
z1 = pColl->zName;
pColl = sqlite3ExprCollSeq(pWInfo->pParse, pTerm->pExpr);
if( !pColl ) pColl = db->pDfltColl;
z2 = pColl->zName;
if( sqlite3StrICmp(z1, z2)!=0 ) continue;
}
obSat |= MASKBIT(i);
}
if( (pLoop->wsFlags & WHERE_ONEROW)==0 ){
if( pLoop->wsFlags & WHERE_IPK ){
pIndex = 0;
nColumn = 0;
}else if( (pIndex = pLoop->u.btree.pIndex)==0 || pIndex->bUnordered ){
return 0;
}else{
nColumn = pIndex->nColumn;
isOrderDistinct = pIndex->onError!=OE_None;
}
/* Loop through all columns of the index and deal with the ones
** that are not constrained by == or IN.
*/
rev = revSet = 0;
distinctColumns = 0;
for(j=0; j<=nColumn; j++){
u8 bOnce; /* True to run the ORDER BY search loop */
/* Skip over == and IS NULL terms */
if( j<pLoop->u.btree.nEq
&& ((i = pLoop->aLTerm[j]->eOperator) & (WO_EQ|WO_ISNULL))!=0
){
if( i & WO_ISNULL ){
testcase( isOrderDistinct );
isOrderDistinct = 0;
}
continue;
}
/* Get the column number in the table (iColumn) and sort order
** (revIdx) for the j-th column of the index.
*/
if( j<nColumn ){
/* Normal index columns */
iColumn = pIndex->aiColumn[j];
revIdx = pIndex->aSortOrder[j];
if( iColumn==pIndex->pTable->iPKey ) iColumn = -1;
}else{
/* The ROWID column at the end */
assert( j==nColumn );
iColumn = -1;
revIdx = 0;
}
/* An unconstrained column that might be NULL means that this
** WhereLoop is not well-ordered
*/
if( isOrderDistinct
&& iColumn>=0
&& j>=pLoop->u.btree.nEq
&& pIndex->pTable->aCol[iColumn].notNull==0
){
isOrderDistinct = 0;
}
/* Find the ORDER BY term that corresponds to the j-th column
** of the index and and mark that ORDER BY term off
*/
bOnce = 1;
isMatch = 0;
for(i=0; bOnce && i<nOrderBy; i++){
if( MASKBIT(i) & obSat ) continue;
pOBExpr = sqlite3ExprSkipCollate(pOrderBy->a[i].pExpr);
testcase( wctrlFlags & WHERE_GROUPBY );
testcase( wctrlFlags & WHERE_DISTINCTBY );
if( (wctrlFlags & (WHERE_GROUPBY|WHERE_DISTINCTBY))==0 ) bOnce = 0;
if( pOBExpr->op!=TK_COLUMN ) continue;
if( pOBExpr->iTable!=iCur ) continue;
if( pOBExpr->iColumn!=iColumn ) continue;
if( iColumn>=0 ){
pColl = sqlite3ExprCollSeq(pWInfo->pParse, pOrderBy->a[i].pExpr);
if( !pColl ) pColl = db->pDfltColl;
if( sqlite3StrICmp(pColl->zName, pIndex->azColl[j])!=0 ) continue;
}
isMatch = 1;
break;
}
if( isMatch ){
if( iColumn<0 ){
testcase( distinctColumns==0 );
distinctColumns = 1;
}
obSat |= MASKBIT(i);
if( (pWInfo->wctrlFlags & WHERE_GROUPBY)==0 ){
/* Make sure the sort order is compatible in an ORDER BY clause.
** Sort order is irrelevant for a GROUP BY clause. */
if( revSet ){
if( (rev ^ revIdx)!=pOrderBy->a[i].sortOrder ) return 0;
}else{
rev = revIdx ^ pOrderBy->a[i].sortOrder;
if( rev ) *pRevMask |= MASKBIT(iLoop);
revSet = 1;
}
}
}else{
/* No match found */
if( j==0 || j<nColumn ){
testcase( isOrderDistinct!=0 );
isOrderDistinct = 0;
}
break;
}
} /* end Loop over all index columns */
if( distinctColumns ){
testcase( isOrderDistinct==0 );
isOrderDistinct = 1;
}
} /* end-if not one-row */
/* Mark off any other ORDER BY terms that reference pLoop */
if( isOrderDistinct ){
orderDistinctMask |= pLoop->maskSelf;
for(i=0; i<nOrderBy; i++){
Expr *p;
if( MASKBIT(i) & obSat ) continue;
p = pOrderBy->a[i].pExpr;
if( (exprTableUsage(&pWInfo->sMaskSet, p)&~orderDistinctMask)==0 ){
obSat |= MASKBIT(i);
}
}
}
} /* End the loop over all WhereLoops from outer-most down to inner-most */
if( obSat==obDone ) return 1;
if( !isOrderDistinct ) return 0;
return -1;
}
#ifdef WHERETRACE_ENABLED
/* For debugging use only: */
static const char *wherePathName(WherePath *pPath, int nLoop, WhereLoop *pLast){
static char zName[65];
int i;
for(i=0; i<nLoop; i++){ zName[i] = pPath->aLoop[i]->cId; }
if( pLast ) zName[i++] = pLast->cId;
zName[i] = 0;
return zName;
}
#endif
/*
** Given the list of WhereLoop objects at pWInfo->pLoops, this routine
** attempts to find the lowest cost path that visits each WhereLoop
** once. This path is then loaded into the pWInfo->a[].pWLoop fields.
**
** Assume that the total number of output rows that will need to be sorted
** will be nRowEst (in the 10*log2 representation). Or, ignore sorting
** costs if nRowEst==0.
**
** Return SQLITE_OK on success or SQLITE_NOMEM of a memory allocation
** error occurs.
*/
static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
int mxChoice; /* Maximum number of simultaneous paths tracked */
int nLoop; /* Number of terms in the join */
Parse *pParse; /* Parsing context */
sqlite3 *db; /* The database connection */
int iLoop; /* Loop counter over the terms of the join */
int ii, jj; /* Loop counters */
int mxI = 0; /* Index of next entry to replace */
LogEst rCost; /* Cost of a path */
LogEst nOut; /* Number of outputs */
LogEst mxCost = 0; /* Maximum cost of a set of paths */
LogEst mxOut = 0; /* Maximum nOut value on the set of paths */
LogEst rSortCost; /* Cost to do a sort */
int nTo, nFrom; /* Number of valid entries in aTo[] and aFrom[] */
WherePath *aFrom; /* All nFrom paths at the previous level */
WherePath *aTo; /* The nTo best paths at the current level */
WherePath *pFrom; /* An element of aFrom[] that we are working on */
WherePath *pTo; /* An element of aTo[] that we are working on */
WhereLoop *pWLoop; /* One of the WhereLoop objects */
WhereLoop **pX; /* Used to divy up the pSpace memory */
char *pSpace; /* Temporary memory used by this routine */
pParse = pWInfo->pParse;
db = pParse->db;
nLoop = pWInfo->nLevel;
/* TUNING: For simple queries, only the best path is tracked.
** For 2-way joins, the 5 best paths are followed.
** For joins of 3 or more tables, track the 10 best paths */
mxChoice = (nLoop==1) ? 1 : (nLoop==2 ? 5 : 10);
assert( nLoop<=pWInfo->pTabList->nSrc );
WHERETRACE(0x002, ("---- begin solver\n"));
/* Allocate and initialize space for aTo and aFrom */
ii = (sizeof(WherePath)+sizeof(WhereLoop*)*nLoop)*mxChoice*2;
pSpace = sqlite3DbMallocRaw(db, ii);
if( pSpace==0 ) return SQLITE_NOMEM;
aTo = (WherePath*)pSpace;
aFrom = aTo+mxChoice;
memset(aFrom, 0, sizeof(aFrom[0]));
pX = (WhereLoop**)(aFrom+mxChoice);
for(ii=mxChoice*2, pFrom=aTo; ii>0; ii--, pFrom++, pX += nLoop){
pFrom->aLoop = pX;
}
/* Seed the search with a single WherePath containing zero WhereLoops.
**
** TUNING: Do not let the number of iterations go above 25. If the cost
** of computing an automatic index is not paid back within the first 25
** rows, then do not use the automatic index. */
aFrom[0].nRow = MIN(pParse->nQueryLoop, 46); assert( 46==sqlite3LogEst(25) );
nFrom = 1;
/* Precompute the cost of sorting the final result set, if the caller
** to sqlite3WhereBegin() was concerned about sorting */
rSortCost = 0;
if( pWInfo->pOrderBy==0 || nRowEst==0 ){
aFrom[0].isOrderedValid = 1;
}else{
/* TUNING: Estimated cost of sorting is 48*N*log2(N) where N is the
** number of output rows. The 48 is the expected size of a row to sort.
** FIXME: compute a better estimate of the 48 multiplier based on the
** result set expressions. */
rSortCost = nRowEst + estLog(nRowEst);
WHERETRACE(0x002,("---- sort cost=%-3d\n", rSortCost));
}
/* Compute successively longer WherePaths using the previous generation
** of WherePaths as the basis for the next. Keep track of the mxChoice
** best paths at each generation */
for(iLoop=0; iLoop<nLoop; iLoop++){
nTo = 0;
for(ii=0, pFrom=aFrom; ii<nFrom; ii++, pFrom++){
for(pWLoop=pWInfo->pLoops; pWLoop; pWLoop=pWLoop->pNextLoop){
Bitmask maskNew;
Bitmask revMask = 0;
u8 isOrderedValid = pFrom->isOrderedValid;
u8 isOrdered = pFrom->isOrdered;
if( (pWLoop->prereq & ~pFrom->maskLoop)!=0 ) continue;
if( (pWLoop->maskSelf & pFrom->maskLoop)!=0 ) continue;
/* At this point, pWLoop is a candidate to be the next loop.
** Compute its cost */
rCost = sqlite3LogEstAdd(pWLoop->rSetup,pWLoop->rRun + pFrom->nRow);
rCost = sqlite3LogEstAdd(rCost, pFrom->rCost);
nOut = pFrom->nRow + pWLoop->nOut;
maskNew = pFrom->maskLoop | pWLoop->maskSelf;
if( !isOrderedValid ){
switch( wherePathSatisfiesOrderBy(pWInfo,
pWInfo->pOrderBy, pFrom, pWInfo->wctrlFlags,
iLoop, pWLoop, &revMask) ){
case 1: /* Yes. pFrom+pWLoop does satisfy the ORDER BY clause */
isOrdered = 1;
isOrderedValid = 1;
break;
case 0: /* No. pFrom+pWLoop will require a separate sort */
isOrdered = 0;
isOrderedValid = 1;
rCost = sqlite3LogEstAdd(rCost, rSortCost);
break;
default: /* Cannot tell yet. Try again on the next iteration */
break;
}
}else{
revMask = pFrom->revLoop;
}
/* Check to see if pWLoop should be added to the mxChoice best so far */
for(jj=0, pTo=aTo; jj<nTo; jj++, pTo++){
if( pTo->maskLoop==maskNew
&& pTo->isOrderedValid==isOrderedValid
&& ((pTo->rCost<=rCost && pTo->nRow<=nOut) ||
(pTo->rCost>=rCost && pTo->nRow>=nOut))
){
testcase( jj==nTo-1 );
break;
}
}
if( jj>=nTo ){
if( nTo>=mxChoice && rCost>=mxCost ){
#ifdef WHERETRACE_ENABLED
if( sqlite3WhereTrace&0x4 ){
sqlite3DebugPrintf("Skip %s cost=%-3d,%3d order=%c\n",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
}
#endif
continue;
}
/* Add a new Path to the aTo[] set */
if( nTo<mxChoice ){
/* Increase the size of the aTo set by one */
jj = nTo++;
}else{
/* New path replaces the prior worst to keep count below mxChoice */
jj = mxI;
}
pTo = &aTo[jj];
#ifdef WHERETRACE_ENABLED
if( sqlite3WhereTrace&0x4 ){
sqlite3DebugPrintf("New %s cost=%-3d,%3d order=%c\n",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
}
#endif
}else{
if( pTo->rCost<=rCost && pTo->nRow<=nOut ){
#ifdef WHERETRACE_ENABLED
if( sqlite3WhereTrace&0x4 ){
sqlite3DebugPrintf(
"Skip %s cost=%-3d,%3d order=%c",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
sqlite3DebugPrintf(" vs %s cost=%-3d,%d order=%c\n",
wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
}
#endif
testcase( pTo->rCost==rCost );
continue;
}
testcase( pTo->rCost==rCost+1 );
/* A new and better score for a previously created equivalent path */
#ifdef WHERETRACE_ENABLED
if( sqlite3WhereTrace&0x4 ){
sqlite3DebugPrintf(
"Update %s cost=%-3d,%3d order=%c",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
sqlite3DebugPrintf(" was %s cost=%-3d,%3d order=%c\n",
wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
}
#endif
}
/* pWLoop is a winner. Add it to the set of best so far */
pTo->maskLoop = pFrom->maskLoop | pWLoop->maskSelf;
pTo->revLoop = revMask;
pTo->nRow = nOut;
pTo->rCost = rCost;
pTo->isOrderedValid = isOrderedValid;
pTo->isOrdered = isOrdered;
memcpy(pTo->aLoop, pFrom->aLoop, sizeof(WhereLoop*)*iLoop);
pTo->aLoop[iLoop] = pWLoop;
if( nTo>=mxChoice ){
mxI = 0;
mxCost = aTo[0].rCost;
mxOut = aTo[0].nRow;
for(jj=1, pTo=&aTo[1]; jj<mxChoice; jj++, pTo++){
if( pTo->rCost>mxCost || (pTo->rCost==mxCost && pTo->nRow>mxOut) ){
mxCost = pTo->rCost;
mxOut = pTo->nRow;
mxI = jj;
}
}
}
}
}
#ifdef WHERETRACE_ENABLED
if( sqlite3WhereTrace>=2 ){
sqlite3DebugPrintf("---- after round %d ----\n", iLoop);
for(ii=0, pTo=aTo; ii<nTo; ii++, pTo++){
sqlite3DebugPrintf(" %s cost=%-3d nrow=%-3d order=%c",
wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
if( pTo->isOrderedValid && pTo->isOrdered ){
sqlite3DebugPrintf(" rev=0x%llx\n", pTo->revLoop);
}else{
sqlite3DebugPrintf("\n");
}
}
}
#endif
/* Swap the roles of aFrom and aTo for the next generation */
pFrom = aTo;
aTo = aFrom;
aFrom = pFrom;
nFrom = nTo;
}
if( nFrom==0 ){
sqlite3ErrorMsg(pParse, "no query solution");
sqlite3DbFree(db, pSpace);
return SQLITE_ERROR;
}
/* Find the lowest cost path. pFrom will be left pointing to that path */
pFrom = aFrom;
for(ii=1; ii<nFrom; ii++){
if( pFrom->rCost>aFrom[ii].rCost ) pFrom = &aFrom[ii];
}
assert( pWInfo->nLevel==nLoop );
/* Load the lowest cost path into pWInfo */
for(iLoop=0; iLoop<nLoop; iLoop++){
WhereLevel *pLevel = pWInfo->a + iLoop;
pLevel->pWLoop = pWLoop = pFrom->aLoop[iLoop];
pLevel->iFrom = pWLoop->iTab;
pLevel->iTabCur = pWInfo->pTabList->a[pLevel->iFrom].iCursor;
}
if( (pWInfo->wctrlFlags & WHERE_WANT_DISTINCT)!=0
&& (pWInfo->wctrlFlags & WHERE_DISTINCTBY)==0
&& pWInfo->eDistinct==WHERE_DISTINCT_NOOP
&& nRowEst
){
Bitmask notUsed;
int rc = wherePathSatisfiesOrderBy(pWInfo, pWInfo->pResultSet, pFrom,
WHERE_DISTINCTBY, nLoop-1, pFrom->aLoop[nLoop-1], &notUsed);
if( rc==1 ) pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
}
if( pFrom->isOrdered ){
if( pWInfo->wctrlFlags & WHERE_DISTINCTBY ){
pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
}else{
pWInfo->bOBSat = 1;
pWInfo->revMask = pFrom->revLoop;
}
}
pWInfo->nRowOut = pFrom->nRow;
/* Free temporary memory and return success */
sqlite3DbFree(db, pSpace);
return SQLITE_OK;
}
/*
** Most queries use only a single table (they are not joins) and have
** simple == constraints against indexed fields. This routine attempts
** to plan those simple cases using much less ceremony than the
** general-purpose query planner, and thereby yield faster sqlite3_prepare()
** times for the common case.
**
** Return non-zero on success, if this query can be handled by this
** no-frills query planner. Return zero if this query needs the
** general-purpose query planner.
*/
static int whereShortCut(WhereLoopBuilder *pBuilder){
WhereInfo *pWInfo;
struct SrcList_item *pItem;
WhereClause *pWC;
WhereTerm *pTerm;
WhereLoop *pLoop;
int iCur;
int j;
Table *pTab;
Index *pIdx;
pWInfo = pBuilder->pWInfo;
if( pWInfo->wctrlFlags & WHERE_FORCE_TABLE ) return 0;
assert( pWInfo->pTabList->nSrc>=1 );
pItem = pWInfo->pTabList->a;
pTab = pItem->pTab;
if( IsVirtual(pTab) ) return 0;
if( pItem->zIndex ) return 0;
iCur = pItem->iCursor;
pWC = &pWInfo->sWC;
pLoop = pBuilder->pNew;
pLoop->wsFlags = 0;
pTerm = findTerm(pWC, iCur, -1, 0, WO_EQ, 0);
if( pTerm ){
pLoop->wsFlags = WHERE_COLUMN_EQ|WHERE_IPK|WHERE_ONEROW;
pLoop->aLTerm[0] = pTerm;
pLoop->nLTerm = 1;
pLoop->u.btree.nEq = 1;
/* TUNING: Cost of a rowid lookup is 10 */
pLoop->rRun = 33; /* 33==sqlite3LogEst(10) */
}else{
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
assert( pLoop->aLTermSpace==pLoop->aLTerm );
assert( ArraySize(pLoop->aLTermSpace)==4 );
if( pIdx->onError==OE_None
|| pIdx->pPartIdxWhere!=0
|| pIdx->nColumn>ArraySize(pLoop->aLTermSpace)
) continue;
for(j=0; j<pIdx->nColumn; j++){
pTerm = findTerm(pWC, iCur, pIdx->aiColumn[j], 0, WO_EQ, pIdx);
if( pTerm==0 ) break;
pLoop->aLTerm[j] = pTerm;
}
if( j!=pIdx->nColumn ) continue;
pLoop->wsFlags = WHERE_COLUMN_EQ|WHERE_ONEROW|WHERE_INDEXED;
if( (pItem->colUsed & ~columnsInIndex(pIdx))==0 ){
pLoop->wsFlags |= WHERE_IDX_ONLY;
}
pLoop->nLTerm = j;
pLoop->u.btree.nEq = j;
pLoop->u.btree.pIndex = pIdx;
/* TUNING: Cost of a unique index lookup is 15 */
pLoop->rRun = 39; /* 39==sqlite3LogEst(15) */
break;
}
}
if( pLoop->wsFlags ){
pLoop->nOut = (LogEst)1;
pWInfo->a[0].pWLoop = pLoop;
pLoop->maskSelf = getMask(&pWInfo->sMaskSet, iCur);
pWInfo->a[0].iTabCur = iCur;
pWInfo->nRowOut = 1;
if( pWInfo->pOrderBy ) pWInfo->bOBSat = 1;
if( pWInfo->wctrlFlags & WHERE_WANT_DISTINCT ){
pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
}
#ifdef SQLITE_DEBUG
pLoop->cId = '0';
#endif
return 1;
}
return 0;
}
/*
** Generate the beginning of the loop used for WHERE clause processing.
** The return value is a pointer to an opaque structure that contains
** information needed to terminate the loop. Later, the calling routine
** should invoke sqlite3WhereEnd() with the return value of this function
** in order to complete the WHERE clause processing.
**
** If an error occurs, this routine returns NULL.
**
** The basic idea is to do a nested loop, one loop for each table in
** the FROM clause of a select. (INSERT and UPDATE statements are the
** same as a SELECT with only a single table in the FROM clause.) For
** example, if the SQL is this:
**
** SELECT * FROM t1, t2, t3 WHERE ...;
**
** Then the code generated is conceptually like the following:
**
** foreach row1 in t1 do \ Code generated
** foreach row2 in t2 do |-- by sqlite3WhereBegin()
** foreach row3 in t3 do /
** ...
** end \ Code generated
** end |-- by sqlite3WhereEnd()
** end /
**
** Note that the loops might not be nested in the order in which they
** appear in the FROM clause if a different order is better able to make
** use of indices. Note also that when the IN operator appears in
** the WHERE clause, it might result in additional nested loops for
** scanning through all values on the right-hand side of the IN.
**
** There are Btree cursors associated with each table. t1 uses cursor
** number pTabList->a[0].iCursor. t2 uses the cursor pTabList->a[1].iCursor.
** And so forth. This routine generates code to open those VDBE cursors
** and sqlite3WhereEnd() generates the code to close them.
**
** The code that sqlite3WhereBegin() generates leaves the cursors named
** in pTabList pointing at their appropriate entries. The [...] code
** can use OP_Column and OP_Rowid opcodes on these cursors to extract
** data from the various tables of the loop.
**
** If the WHERE clause is empty, the foreach loops must each scan their
** entire tables. Thus a three-way join is an O(N^3) operation. But if
** the tables have indices and there are terms in the WHERE clause that
** refer to those indices, a complete table scan can be avoided and the
** code will run much faster. Most of the work of this routine is checking
** to see if there are indices that can be used to speed up the loop.
**
** Terms of the WHERE clause are also used to limit which rows actually
** make it to the "..." in the middle of the loop. After each "foreach",
** terms of the WHERE clause that use only terms in that loop and outer
** loops are evaluated and if false a jump is made around all subsequent
** inner loops (or around the "..." if the test occurs within the inner-
** most loop)
**
** OUTER JOINS
**
** An outer join of tables t1 and t2 is conceptally coded as follows:
**
** foreach row1 in t1 do
** flag = 0
** foreach row2 in t2 do
** start:
** ...
** flag = 1
** end
** if flag==0 then
** move the row2 cursor to a null row
** goto start
** fi
** end
**
** ORDER BY CLAUSE PROCESSING
**
** pOrderBy is a pointer to the ORDER BY clause (or the GROUP BY clause
** if the WHERE_GROUPBY flag is set in wctrlFlags) of a SELECT statement
** if there is one. If there is no ORDER BY clause or if this routine
** is called from an UPDATE or DELETE statement, then pOrderBy is NULL.
*/
WhereInfo *sqlite3WhereBegin(
Parse *pParse, /* The parser context */
SrcList *pTabList, /* FROM clause: A list of all tables to be scanned */
Expr *pWhere, /* The WHERE clause */
ExprList *pOrderBy, /* An ORDER BY clause, or NULL */
ExprList *pResultSet, /* Result set of the query */
u16 wctrlFlags, /* One of the WHERE_* flags defined in sqliteInt.h */
int iIdxCur /* If WHERE_ONETABLE_ONLY is set, index cursor number */
){
int nByteWInfo; /* Num. bytes allocated for WhereInfo struct */
int nTabList; /* Number of elements in pTabList */
WhereInfo *pWInfo; /* Will become the return value of this function */
Vdbe *v = pParse->pVdbe; /* The virtual database engine */
Bitmask notReady; /* Cursors that are not yet positioned */
WhereLoopBuilder sWLB; /* The WhereLoop builder */
WhereMaskSet *pMaskSet; /* The expression mask set */
WhereLevel *pLevel; /* A single level in pWInfo->a[] */
WhereLoop *pLoop; /* Pointer to a single WhereLoop object */
int ii; /* Loop counter */
sqlite3 *db; /* Database connection */
int rc; /* Return code */
/* Variable initialization */
db = pParse->db;
memset(&sWLB, 0, sizeof(sWLB));
sWLB.pOrderBy = pOrderBy;
/* Disable the DISTINCT optimization if SQLITE_DistinctOpt is set via
** sqlite3_test_ctrl(SQLITE_TESTCTRL_OPTIMIZATIONS,...) */
if( OptimizationDisabled(db, SQLITE_DistinctOpt) ){
wctrlFlags &= ~WHERE_WANT_DISTINCT;
}
/* The number of tables in the FROM clause is limited by the number of
** bits in a Bitmask
*/
testcase( pTabList->nSrc==BMS );
if( pTabList->nSrc>BMS ){
sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
return 0;
}
/* This function normally generates a nested loop for all tables in
** pTabList. But if the WHERE_ONETABLE_ONLY flag is set, then we should
** only generate code for the first table in pTabList and assume that
** any cursors associated with subsequent tables are uninitialized.
*/
nTabList = (wctrlFlags & WHERE_ONETABLE_ONLY) ? 1 : pTabList->nSrc;
/* Allocate and initialize the WhereInfo structure that will become the
** return value. A single allocation is used to store the WhereInfo
** struct, the contents of WhereInfo.a[], the WhereClause structure
** and the WhereMaskSet structure. Since WhereClause contains an 8-byte
** field (type Bitmask) it must be aligned on an 8-byte boundary on
** some architectures. Hence the ROUND8() below.
*/
nByteWInfo = ROUND8(sizeof(WhereInfo)+(nTabList-1)*sizeof(WhereLevel));
pWInfo = sqlite3DbMallocZero(db, nByteWInfo + sizeof(WhereLoop));
if( db->mallocFailed ){
sqlite3DbFree(db, pWInfo);
pWInfo = 0;
goto whereBeginError;
}
pWInfo->nLevel = nTabList;
pWInfo->pParse = pParse;
pWInfo->pTabList = pTabList;
pWInfo->pOrderBy = pOrderBy;
pWInfo->pResultSet = pResultSet;
pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
pWInfo->wctrlFlags = wctrlFlags;
pWInfo->savedNQueryLoop = pParse->nQueryLoop;
pMaskSet = &pWInfo->sMaskSet;
sWLB.pWInfo = pWInfo;
sWLB.pWC = &pWInfo->sWC;
sWLB.pNew = (WhereLoop*)(((char*)pWInfo)+nByteWInfo);
assert( EIGHT_BYTE_ALIGNMENT(sWLB.pNew) );
whereLoopInit(sWLB.pNew);
#ifdef SQLITE_DEBUG
sWLB.pNew->cId = '*';
#endif
/* Split the WHERE clause into separate subexpressions where each
** subexpression is separated by an AND operator.
*/
initMaskSet(pMaskSet);
whereClauseInit(&pWInfo->sWC, pWInfo);
sqlite3ExprCodeConstants(pParse, pWhere);
whereSplit(&pWInfo->sWC, pWhere, TK_AND);
sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
/* Special case: a WHERE clause that is constant. Evaluate the
** expression and either jump over all of the code or fall thru.
*/
if( pWhere && (nTabList==0 || sqlite3ExprIsConstantNotJoin(pWhere)) ){
sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, SQLITE_JUMPIFNULL);
pWhere = 0;
}
/* Special case: No FROM clause
*/
if( nTabList==0 ){
if( pOrderBy ) pWInfo->bOBSat = 1;
if( wctrlFlags & WHERE_WANT_DISTINCT ){
pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
}
}
/* Assign a bit from the bitmask to every term in the FROM clause.
**
** When assigning bitmask values to FROM clause cursors, it must be
** the case that if X is the bitmask for the N-th FROM clause term then
** the bitmask for all FROM clause terms to the left of the N-th term
** is (X-1). An expression from the ON clause of a LEFT JOIN can use
** its Expr.iRightJoinTable value to find the bitmask of the right table
** of the join. Subtracting one from the right table bitmask gives a
** bitmask for all tables to the left of the join. Knowing the bitmask
** for all tables to the left of a left join is important. Ticket #3015.
**
** Note that bitmasks are created for all pTabList->nSrc tables in
** pTabList, not just the first nTabList tables. nTabList is normally
** equal to pTabList->nSrc but might be shortened to 1 if the
** WHERE_ONETABLE_ONLY flag is set.
*/
for(ii=0; ii<pTabList->nSrc; ii++){
createMask(pMaskSet, pTabList->a[ii].iCursor);
}
#ifndef NDEBUG
{
Bitmask toTheLeft = 0;
for(ii=0; ii<pTabList->nSrc; ii++){
Bitmask m = getMask(pMaskSet, pTabList->a[ii].iCursor);
assert( (m-1)==toTheLeft );
toTheLeft |= m;
}
}
#endif
/* Analyze all of the subexpressions. Note that exprAnalyze() might
** add new virtual terms onto the end of the WHERE clause. We do not
** want to analyze these virtual terms, so start analyzing at the end
** and work forward so that the added virtual terms are never processed.
*/
exprAnalyzeAll(pTabList, &pWInfo->sWC);
if( db->mallocFailed ){
goto whereBeginError;
}
/* If the ORDER BY (or GROUP BY) clause contains references to general
** expressions, then we won't be able to satisfy it using indices, so
** go ahead and disable it now.
*/
if( pOrderBy && (wctrlFlags & WHERE_WANT_DISTINCT)!=0 ){
for(ii=0; ii<pOrderBy->nExpr; ii++){
Expr *pExpr = sqlite3ExprSkipCollate(pOrderBy->a[ii].pExpr);
if( pExpr->op!=TK_COLUMN ){
pWInfo->pOrderBy = pOrderBy = 0;
break;
}else if( pExpr->iColumn<0 ){
break;
}
}
}
if( wctrlFlags & WHERE_WANT_DISTINCT ){
if( isDistinctRedundant(pParse, pTabList, &pWInfo->sWC, pResultSet) ){
/* The DISTINCT marking is pointless. Ignore it. */
pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
}else if( pOrderBy==0 ){
/* Try to ORDER BY the result set to make distinct processing easier */
pWInfo->wctrlFlags |= WHERE_DISTINCTBY;
pWInfo->pOrderBy = pResultSet;
}
}
/* Construct the WhereLoop objects */
WHERETRACE(0xffff,("*** Optimizer Start ***\n"));
if( nTabList!=1 || whereShortCut(&sWLB)==0 ){
rc = whereLoopAddAll(&sWLB);
if( rc ) goto whereBeginError;
/* Display all of the WhereLoop objects if wheretrace is enabled */
#ifdef WHERETRACE_ENABLED
if( sqlite3WhereTrace ){
WhereLoop *p;
int i;
static char zLabel[] = "0123456789abcdefghijklmnopqrstuvwyxz"
"ABCDEFGHIJKLMNOPQRSTUVWYXZ";
for(p=pWInfo->pLoops, i=0; p; p=p->pNextLoop, i++){
p->cId = zLabel[i%sizeof(zLabel)];
whereLoopPrint(p, pTabList);
}
}
#endif
wherePathSolver(pWInfo, 0);
if( db->mallocFailed ) goto whereBeginError;
if( pWInfo->pOrderBy ){
wherePathSolver(pWInfo, pWInfo->nRowOut+1);
if( db->mallocFailed ) goto whereBeginError;
}
}
if( pWInfo->pOrderBy==0 && (db->flags & SQLITE_ReverseOrder)!=0 ){
pWInfo->revMask = (Bitmask)(-1);
}
if( pParse->nErr || NEVER(db->mallocFailed) ){
goto whereBeginError;
}
#ifdef WHERETRACE_ENABLED
if( sqlite3WhereTrace ){
int ii;
sqlite3DebugPrintf("---- Solution nRow=%d", pWInfo->nRowOut);
if( pWInfo->bOBSat ){
sqlite3DebugPrintf(" ORDERBY=0x%llx", pWInfo->revMask);
}
switch( pWInfo->eDistinct ){
case WHERE_DISTINCT_UNIQUE: {
sqlite3DebugPrintf(" DISTINCT=unique");
break;
}
case WHERE_DISTINCT_ORDERED: {
sqlite3DebugPrintf(" DISTINCT=ordered");
break;
}
case WHERE_DISTINCT_UNORDERED: {
sqlite3DebugPrintf(" DISTINCT=unordered");
break;
}
}
sqlite3DebugPrintf("\n");
for(ii=0; ii<pWInfo->nLevel; ii++){
whereLoopPrint(pWInfo->a[ii].pWLoop, pTabList);
}
}
#endif
/* Attempt to omit tables from the join that do not effect the result */
if( pWInfo->nLevel>=2
&& pResultSet!=0
&& OptimizationEnabled(db, SQLITE_OmitNoopJoin)
){
Bitmask tabUsed = exprListTableUsage(pMaskSet, pResultSet);
if( sWLB.pOrderBy ) tabUsed |= exprListTableUsage(pMaskSet, sWLB.pOrderBy);
while( pWInfo->nLevel>=2 ){
WhereTerm *pTerm, *pEnd;
pLoop = pWInfo->a[pWInfo->nLevel-1].pWLoop;
if( (pWInfo->pTabList->a[pLoop->iTab].jointype & JT_LEFT)==0 ) break;
if( (wctrlFlags & WHERE_WANT_DISTINCT)==0
&& (pLoop->wsFlags & WHERE_ONEROW)==0
){
break;
}
if( (tabUsed & pLoop->maskSelf)!=0 ) break;
pEnd = sWLB.pWC->a + sWLB.pWC->nTerm;
for(pTerm=sWLB.pWC->a; pTerm<pEnd; pTerm++){
if( (pTerm->prereqAll & pLoop->maskSelf)!=0
&& !ExprHasProperty(pTerm->pExpr, EP_FromJoin)
){
break;
}
}
if( pTerm<pEnd ) break;
WHERETRACE(0xffff, ("-> drop loop %c not used\n", pLoop->cId));
pWInfo->nLevel--;
nTabList--;
}
}
WHERETRACE(0xffff,("*** Optimizer Finished ***\n"));
pWInfo->pParse->nQueryLoop += pWInfo->nRowOut;
/* If the caller is an UPDATE or DELETE statement that is requesting
** to use a one-pass algorithm, determine if this is appropriate.
** The one-pass algorithm only works if the WHERE clause constrains
** the statement to update a single row.
*/
assert( (wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0
&& (pWInfo->a[0].pWLoop->wsFlags & WHERE_ONEROW)!=0 ){
pWInfo->okOnePass = 1;
pWInfo->a[0].pWLoop->wsFlags &= ~WHERE_IDX_ONLY;
}
/* Open all tables in the pTabList and any indices selected for
** searching those tables.
*/
notReady = ~(Bitmask)0;
for(ii=0, pLevel=pWInfo->a; ii<nTabList; ii++, pLevel++){
Table *pTab; /* Table to open */
int iDb; /* Index of database containing table/index */
struct SrcList_item *pTabItem;
pTabItem = &pTabList->a[pLevel->iFrom];
pTab = pTabItem->pTab;
iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
pLoop = pLevel->pWLoop;
if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
/* Do nothing */
}else
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
int iCur = pTabItem->iCursor;
sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0, pVTab, P4_VTAB);
}else if( IsVirtual(pTab) ){
/* noop */
}else
#endif
if( (pLoop->wsFlags & WHERE_IDX_ONLY)==0
&& (wctrlFlags & WHERE_OMIT_OPEN_CLOSE)==0 ){
int op = pWInfo->okOnePass ? OP_OpenWrite : OP_OpenRead;
sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
testcase( !pWInfo->okOnePass && pTab->nCol==BMS-1 );
testcase( !pWInfo->okOnePass && pTab->nCol==BMS );
if( !pWInfo->okOnePass && pTab->nCol<BMS ){
Bitmask b = pTabItem->colUsed;
int n = 0;
for(; b; b=b>>1, n++){}
sqlite3VdbeChangeP4(v, sqlite3VdbeCurrentAddr(v)-1,
SQLITE_INT_TO_PTR(n), P4_INT32);
assert( n<=pTab->nCol );
}
}else{
sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
}
if( pLoop->wsFlags & WHERE_INDEXED ){
Index *pIx = pLoop->u.btree.pIndex;
KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
/* FIXME: As an optimization use pTabItem->iCursor if WHERE_IDX_ONLY */
int iIndexCur = pLevel->iIdxCur = iIdxCur ? iIdxCur : pParse->nTab++;
assert( pIx->pSchema==pTab->pSchema );
assert( iIndexCur>=0 );
sqlite3VdbeAddOp4(v, OP_OpenRead, iIndexCur, pIx->tnum, iDb,
(char*)pKey, P4_KEYINFO_HANDOFF);
VdbeComment((v, "%s", pIx->zName));
}
sqlite3CodeVerifySchema(pParse, iDb);
notReady &= ~getMask(&pWInfo->sMaskSet, pTabItem->iCursor);
}
pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
if( db->mallocFailed ) goto whereBeginError;
/* Generate the code to do the search. Each iteration of the for
** loop below generates code for a single nested loop of the VM
** program.
*/
notReady = ~(Bitmask)0;
for(ii=0; ii<nTabList; ii++){
pLevel = &pWInfo->a[ii];
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
if( (pLevel->pWLoop->wsFlags & WHERE_AUTO_INDEX)!=0 ){
constructAutomaticIndex(pParse, &pWInfo->sWC,
&pTabList->a[pLevel->iFrom], notReady, pLevel);
if( db->mallocFailed ) goto whereBeginError;
}
#endif
explainOneScan(pParse, pTabList, pLevel, ii, pLevel->iFrom, wctrlFlags);
pLevel->addrBody = sqlite3VdbeCurrentAddr(v);
notReady = codeOneLoopStart(pWInfo, ii, notReady);
pWInfo->iContinue = pLevel->addrCont;
}
/* Done. */
return pWInfo;
/* Jump here if malloc fails */
whereBeginError:
if( pWInfo ){
pParse->nQueryLoop = pWInfo->savedNQueryLoop;
whereInfoFree(db, pWInfo);
}
return 0;
}
/*
** Generate the end of the WHERE loop. See comments on
** sqlite3WhereBegin() for additional information.
*/
void sqlite3WhereEnd(WhereInfo *pWInfo){
Parse *pParse = pWInfo->pParse;
Vdbe *v = pParse->pVdbe;
int i;
WhereLevel *pLevel;
WhereLoop *pLoop;
SrcList *pTabList = pWInfo->pTabList;
sqlite3 *db = pParse->db;
/* Generate loop termination code.
*/
sqlite3ExprCacheClear(pParse);
for(i=pWInfo->nLevel-1; i>=0; i--){
pLevel = &pWInfo->a[i];
pLoop = pLevel->pWLoop;
sqlite3VdbeResolveLabel(v, pLevel->addrCont);
if( pLevel->op!=OP_Noop ){
sqlite3VdbeAddOp2(v, pLevel->op, pLevel->p1, pLevel->p2);
sqlite3VdbeChangeP5(v, pLevel->p5);
}
if( pLoop->wsFlags & WHERE_IN_ABLE && pLevel->u.in.nIn>0 ){
struct InLoop *pIn;
int j;
sqlite3VdbeResolveLabel(v, pLevel->addrNxt);
for(j=pLevel->u.in.nIn, pIn=&pLevel->u.in.aInLoop[j-1]; j>0; j--, pIn--){
sqlite3VdbeJumpHere(v, pIn->addrInTop+1);
sqlite3VdbeAddOp2(v, pIn->eEndLoopOp, pIn->iCur, pIn->addrInTop);
sqlite3VdbeJumpHere(v, pIn->addrInTop-1);
}
sqlite3DbFree(db, pLevel->u.in.aInLoop);
}
sqlite3VdbeResolveLabel(v, pLevel->addrBrk);
if( pLevel->iLeftJoin ){
int addr;
addr = sqlite3VdbeAddOp1(v, OP_IfPos, pLevel->iLeftJoin);
assert( (pLoop->wsFlags & WHERE_IDX_ONLY)==0
|| (pLoop->wsFlags & WHERE_INDEXED)!=0 );
if( (pLoop->wsFlags & WHERE_IDX_ONLY)==0 ){
sqlite3VdbeAddOp1(v, OP_NullRow, pTabList->a[i].iCursor);
}
if( pLoop->wsFlags & WHERE_INDEXED ){
sqlite3VdbeAddOp1(v, OP_NullRow, pLevel->iIdxCur);
}
if( pLevel->op==OP_Return ){
sqlite3VdbeAddOp2(v, OP_Gosub, pLevel->p1, pLevel->addrFirst);
}else{
sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrFirst);
}
sqlite3VdbeJumpHere(v, addr);
}
}
/* The "break" point is here, just past the end of the outer loop.
** Set it.
*/
sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
/* Close all of the cursors that were opened by sqlite3WhereBegin.
*/
assert( pWInfo->nLevel<=pTabList->nSrc );
for(i=0, pLevel=pWInfo->a; i<pWInfo->nLevel; i++, pLevel++){
Index *pIdx = 0;
struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
Table *pTab = pTabItem->pTab;
assert( pTab!=0 );
pLoop = pLevel->pWLoop;
if( (pTab->tabFlags & TF_Ephemeral)==0
&& pTab->pSelect==0
&& (pWInfo->wctrlFlags & WHERE_OMIT_OPEN_CLOSE)==0
){
int ws = pLoop->wsFlags;
if( !pWInfo->okOnePass && (ws & WHERE_IDX_ONLY)==0 ){
sqlite3VdbeAddOp1(v, OP_Close, pTabItem->iCursor);
}
if( (ws & WHERE_INDEXED)!=0 && (ws & (WHERE_IPK|WHERE_AUTO_INDEX))==0 ){
sqlite3VdbeAddOp1(v, OP_Close, pLevel->iIdxCur);
}
}
/* If this scan uses an index, make VDBE code substitutions to read data
** from the index instead of from the table where possible. In some cases
** this optimization prevents the table from ever being read, which can
** yield a significant performance boost.
**
** Calls to the code generator in between sqlite3WhereBegin and
** sqlite3WhereEnd will have created code that references the table
** directly. This loop scans all that code looking for opcodes
** that reference the table and converts them into opcodes that
** reference the index.
*/
if( pLoop->wsFlags & (WHERE_INDEXED|WHERE_IDX_ONLY) ){
pIdx = pLoop->u.btree.pIndex;
}else if( pLoop->wsFlags & WHERE_MULTI_OR ){
pIdx = pLevel->u.pCovidx;
}
if( pIdx && !db->mallocFailed ){
int k, j, last;
VdbeOp *pOp;
last = sqlite3VdbeCurrentAddr(v);
k = pLevel->addrBody;
pOp = sqlite3VdbeGetOp(v, k);
for(; k<last; k++, pOp++){
if( pOp->p1!=pLevel->iTabCur ) continue;
if( pOp->opcode==OP_Column ){
for(j=0; j<pIdx->nColumn; j++){
if( pOp->p2==pIdx->aiColumn[j] ){
pOp->p2 = j;
pOp->p1 = pLevel->iIdxCur;
break;
}
}
assert( (pLoop->wsFlags & WHERE_IDX_ONLY)==0 || j<pIdx->nColumn );
}else if( pOp->opcode==OP_Rowid ){
pOp->p1 = pLevel->iIdxCur;
pOp->opcode = OP_IdxRowid;
}
}
}
}
/* Final cleanup
*/
pParse->nQueryLoop = pWInfo->savedNQueryLoop;
whereInfoFree(db, pWInfo);
return;
}
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