239 lines
7.4 KiB
Plaintext
239 lines
7.4 KiB
Plaintext
# 2009 March 11
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#
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# The author disclaims copyright to this source code. In place of
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# a legal notice, here is a blessing:
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#
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# May you do good and not evil.
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# May you find forgiveness for yourself and forgive others.
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# May you share freely, never taking more than you give.
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#
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#***********************************************************************
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#
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# Test a race-condition that shows up in shared-cache mode.
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#
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# $Id: thread005.test,v 1.5 2009/03/26 14:48:07 danielk1977 Exp $
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set testdir [file dirname $argv0]
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source $testdir/tester.tcl
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if {[run_thread_tests]==0} { finish_test ; return }
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ifcapable !shared_cache {
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finish_test
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return
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}
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db close
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# Use shared-cache mode for these tests.
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#
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set ::enable_shared_cache [sqlite3_enable_shared_cache]
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sqlite3_enable_shared_cache 1
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#-------------------------------------------------------------------------
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# This test attempts to hit the race condition fixed by commit [6363].
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#
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proc runsql {zSql {db {}}} {
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set rc SQLITE_OK
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while {$rc=="SQLITE_OK" && $zSql ne ""} {
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set STMT [sqlite3_prepare_v2 $db $zSql -1 zSql]
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while {[set rc [sqlite3_step $STMT]] eq "SQLITE_ROW"} { }
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set rc [sqlite3_finalize $STMT]
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}
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return $rc
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}
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do_test thread005-1.1 {
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sqlite3 db test.db
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db eval { CREATE TABLE t1(a, b) }
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db close
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} {}
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for {set ii 2} {$ii < 500} {incr ii} {
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unset -nocomplain finished
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thread_spawn finished(0) {sqlite3_open test.db}
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thread_spawn finished(1) {sqlite3_open test.db}
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if {![info exists finished(0)]} { vwait finished(0) }
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if {![info exists finished(1)]} { vwait finished(1) }
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do_test thread005-1.$ii {
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runsql { BEGIN } $finished(0)
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runsql { INSERT INTO t1 VALUES(1, 2) } $finished(0)
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# If the race-condition was hit, then $finished(0 and $finished(1)
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# will not use the same pager cache. In this case the next statement
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# can be executed succesfully. However, if the race-condition is not
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# hit, then $finished(1) will be blocked by the write-lock held by
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# $finished(0) on the shared-cache table t1 and the statement will
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# return SQLITE_LOCKED.
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#
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runsql { SELECT * FROM t1 } $finished(1)
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} {SQLITE_LOCKED}
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sqlite3_close $finished(0)
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sqlite3_close $finished(1)
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}
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#-------------------------------------------------------------------------
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# This test tries to exercise a race-condition that existed in shared-cache
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# mode at one point. The test uses two threads; each has a database connection
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# open on the same shared cache. The schema of the database is:
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#
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# CREATE TABLE t1(a INTEGER PRIMARY KEY, b UNIQUE);
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#
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# One thread is a reader and the other thread a reader and a writer. The
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# writer thread repeats the following transaction as fast as possible:
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#
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# BEGIN;
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# DELETE FROM t1 WHERE a = (SELECT max(a) FROM t1);
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# INSERT INTO t1 VALUES(NULL, NULL);
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# UPDATE t1 SET b = a WHERE a = (SELECT max(a) FROM t1);
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# SELECT count(*) FROM t1 WHERE b IS NULL;
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# COMMIT;
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#
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# The reader thread does the following over and over as fast as possible:
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#
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# BEGIN;
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# SELECT count(*) FROM t1 WHERE b IS NULL;
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# COMMIT;
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#
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# The test runs for 20 seconds or until one of the "SELECT count(*)"
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# statements returns a non-zero value. If an SQLITE_LOCKED error occurs,
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# the connection issues a ROLLBACK immediately to abandon the current
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# transaction.
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#
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# If everything is working correctly, the "SELECT count(*)" statements
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# should never return a value other than 0. The "INSERT" statement
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# executed by the writer adds a row with "b IS NULL" to the table, but
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# the subsequent UPDATE statement sets its "b" value to an integer
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# immediately afterwards.
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#
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# However, before the race-condition was fixed, if the reader's SELECT
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# statement hit an error (say an SQLITE_LOCKED) at the same time as the
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# writer was executing the UPDATE statement, then it could incorrectly
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# rollback the statement-transaction belonging to the UPDATE statement.
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# The UPDATE statement would still be reported as successful to the user,
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# but it would have no effect on the database contents.
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#
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# Note that it has so far only proved possible to hit this race-condition
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# when using an ATTACHed database. There doesn't seem to be any reason
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# for this, other than that operating on an ATTACHed database means there
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# are a few more mutex grabs and releases during the window of time open
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# for the race-condition. Maybe this encourages the scheduler to context
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# switch or something...
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#
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forcedelete test.db test2.db
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unset -nocomplain finished
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do_test thread005-2.1 {
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sqlite3 db test.db
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execsql { ATTACH 'test2.db' AS aux }
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execsql {
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CREATE TABLE aux.t1(a INTEGER PRIMARY KEY, b UNIQUE);
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INSERT INTO t1 VALUES(1, 1);
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INSERT INTO t1 VALUES(2, 2);
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}
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db close
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} {}
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set ThreadProgram {
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proc execsql {zSql {db {}}} {
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if {$db eq ""} {set db $::DB}
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set lRes [list]
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set rc SQLITE_OK
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while {$rc=="SQLITE_OK" && $zSql ne ""} {
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set STMT [sqlite3_prepare_v2 $db $zSql -1 zSql]
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while {[set rc [sqlite3_step $STMT]] eq "SQLITE_ROW"} {
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for {set i 0} {$i < [sqlite3_column_count $STMT]} {incr i} {
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lappend lRes [sqlite3_column_text $STMT 0]
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}
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}
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set rc [sqlite3_finalize $STMT]
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}
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if {$rc != "SQLITE_OK"} { error "$rc [sqlite3_errmsg $db]" }
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return $lRes
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}
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if {$isWriter} {
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set Sql {
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BEGIN;
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DELETE FROM t1 WHERE a = (SELECT max(a) FROM t1);
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INSERT INTO t1 VALUES(NULL, NULL);
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UPDATE t1 SET b = a WHERE a = (SELECT max(a) FROM t1);
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SELECT count(*) FROM t1 WHERE b IS NULL;
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COMMIT;
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}
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} else {
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set Sql {
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BEGIN;
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SELECT count(*) FROM t1 WHERE b IS NULL;
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COMMIT;
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}
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}
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set ::DB [sqlite3_open test.db]
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execsql { ATTACH 'test2.db' AS aux }
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set result "ok"
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set finish [expr [clock_seconds]+5]
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while {$result eq "ok" && [clock_seconds] < $finish} {
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set rc [catch {execsql $Sql} msg]
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if {$rc} {
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if {[string match "SQLITE_LOCKED*" $msg]} {
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catch { execsql ROLLBACK }
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} else {
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sqlite3_close $::DB
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error $msg
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}
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} elseif {$msg ne "0"} {
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set result "failed"
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}
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}
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sqlite3_close $::DB
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set result
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}
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# There is a race-condition in btree.c that means that if two threads
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# attempt to open the same database at roughly the same time, and there
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# does not already exist a shared-cache corresponding to that database,
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# then two shared-caches can be created instead of one. Things still more
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# or less work, but the two database connections do not use the same
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# shared-cache.
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#
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# If the threads run by this test hit this race-condition, the tests
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# fail (because SQLITE_BUSY may be unexpectedly returned instead of
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# SQLITE_LOCKED). To prevent this from happening, open a couple of
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# connections to test.db and test2.db now to make sure that there are
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# already shared-caches in memory for all databases opened by the
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# test threads.
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#
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sqlite3 db test.db
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sqlite3 db test2.db
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puts "Running thread-tests for ~20 seconds"
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thread_spawn finished(0) {set isWriter 0} $ThreadProgram
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thread_spawn finished(1) {set isWriter 1} $ThreadProgram
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if {![info exists finished(0)]} { vwait finished(0) }
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if {![info exists finished(1)]} { vwait finished(1) }
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catch { db close }
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catch { db2 close }
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do_test thread005-2.2 {
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list $finished(0) $finished(1)
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} {ok ok}
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do_test thread005-2.3 {
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sqlite3 db test.db
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execsql { ATTACH 'test2.db' AS aux }
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execsql { SELECT count(*) FROM t1 WHERE b IS NULL }
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} {0}
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sqlite3_enable_shared_cache $::enable_shared_cache
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finish_test
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