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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

Artifact de967898652e71de7e5bc1659e4edabaca4a2f7b:


# 2007 December 20
#
# 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.
#
#***********************************************************************
#
# $Id: tkt2854.test,v 1.2 2008/05/20 13:17:28 shane Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl
db close

ifcapable !shared_cache {
  finish_test
  return
}

set ::enable_shared_cache [sqlite3_enable_shared_cache 1]

# Open 3 database connections. Connection "db" and "db2" share a cache.
# Connection "db3" has its own cache.
#
do_test tkt2854-1.1 {
  sqlite3 db test.db
  sqlite3 db2 test.db

  # This is taken from shared.test.  The Windows VFS expands 
  # ./test.db (and test.db) to be the same thing so the path
  # matches and they share a cache.  By changing the case 
  # for Windows platform, we get around this and get a separate
  # connection.
  if {$::tcl_platform(platform)=="unix"} {
    sqlite3 db3 ./test.db
  } else {
    sqlite3 db3 TEST.DB
  }

  db eval {
    CREATE TABLE abc(a, b, c);
  }
} {}

# Check that an exclusive lock cannot be obtained if some other 
# shared-cache connection has a read-lock on a table.
#
do_test tkt2854-1.2 {
  execsql { 
    BEGIN;
    SELECT * FROM abc;
  } db2
} {}
do_test tkt2854-1.3 {
  catchsql { BEGIN EXCLUSIVE } db
} {1 {database is locked}}
do_test tkt2854-1.4 {
  execsql { SELECT * FROM abc } db3
} {}
do_test tkt2854-1.5 {
  catchsql { INSERT INTO abc VALUES(1, 2, 3) } db3
} {1 {database is locked}}
do_test tkt2854-1.6 {
  execsql { COMMIT } db2
} {}

# Check that an exclusive lock prevents other shared-cache users from
# starting a transaction.
#
do_test tkt2854-1.7 {
  set ::DB2 [sqlite3_connection_pointer db2]
  set ::STMT1 [sqlite3_prepare $DB2 "SELECT * FROM abc" -1 TAIL]
  set ::STMT2 [sqlite3_prepare $DB2 "BEGIN EXCLUSIVE" -1 TAIL]
  set ::STMT3 [sqlite3_prepare $DB2 "BEGIN IMMEDIATE" -1 TAIL]
  set ::STMT4 [sqlite3_prepare $DB2 "BEGIN" -1 TAIL]
  set ::STMT5 [sqlite3_prepare $DB2 "COMMIT" -1 TAIL]
  execsql { BEGIN EXCLUSIVE } db
} {}
do_test tkt2854-1.8 {
  catchsql { BEGIN EXCLUSIVE } db2
} {1 {database schema is locked: main}}
do_test tkt2854-1.9 {
  catchsql { BEGIN IMMEDIATE } db2
} {1 {database schema is locked: main}}
do_test tkt2854-1.10 {
  # This fails because the schema of main cannot be verified.
  catchsql { BEGIN } db2
} {1 {database schema is locked: main}}

# Check that an exclusive lock prevents other shared-cache users from
# reading the database. Use stored statements so that the error occurs
# at the b-tree level, not the schema level.
#
do_test tkt2854-1.11 {
  list [sqlite3_step $::STMT1] [sqlite3_finalize $::STMT1]
} {SQLITE_ERROR SQLITE_LOCKED}
do_test tkt2854-1.12 {
  list [sqlite3_step $::STMT2] [sqlite3_finalize $::STMT2]
} {SQLITE_BUSY SQLITE_BUSY}
do_test tkt2854-1.13 {
  list [sqlite3_step $::STMT3] [sqlite3_finalize $::STMT3]
} {SQLITE_BUSY SQLITE_BUSY}
do_test tkt2854-1.14 {
  # A regular "BEGIN" doesn't touch any databases. So it succeeds.
  list [sqlite3_step $::STMT4] [sqlite3_finalize $::STMT4]
} {SQLITE_DONE SQLITE_OK}
do_test tkt2854-1.15 {
  # As does a COMMIT.
  list [sqlite3_step $::STMT5] [sqlite3_finalize $::STMT5]
} {SQLITE_DONE SQLITE_OK}

# Try to read the database using connection "db3" (which does not share
# a cache with "db"). The database should be locked.
do_test tkt2854-1.16 {
  catchsql { SELECT * FROM abc } db3
} {1 {database is locked}}
do_test tkt2854-1.17 {
  execsql { COMMIT } db
} {}
do_test tkt2854-1.18 {
  execsql { SELECT * FROM abc } db2
} {}

# Check that if an attempt to obtain an exclusive lock fails because an
# attached db cannot be locked, the internal exclusive flag used by
# shared-cache users is correctly cleared.
do_test tkt2854-1.19 {
  file delete -force test2.db test2.db-journal
  sqlite3 db4 test2.db
  execsql { CREATE TABLE def(d, e, f) } db4
  execsql { ATTACH 'test2.db' AS aux } db
} {}
do_test tkt2854-1.20 {
  execsql {BEGIN IMMEDIATE} db4
  catchsql {BEGIN EXCLUSIVE} db
} {1 {database is locked}}
do_test tkt2854-1.21 {
  execsql {SELECT * FROM abc} db2
} {}

db close
db2 close
db3 close
db4 close
sqlite3_enable_shared_cache $::enable_shared_cache
finish_test