/ Check-in [25585069]
Login

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Clarify an assert in sqlite3WalExclusiveMode().
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 255850699ddbf4aad8cc3223aefbada35daa0703
User & Date: dan 2010-06-04 18:38:00
Context
2010-06-05
11:53
Add extra coverage test cases for wal.c. No changes to production code. check-in: f9d4ae0e user: dan tags: trunk
2010-06-04
18:38
Clarify an assert in sqlite3WalExclusiveMode(). check-in: 25585069 user: dan tags: trunk
17:16
Remove an unnecessary branch from wal.c. check-in: 8e54786c user: dan tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/wal.c.

2444
2445
2446
2447
2448
2449
2450

2451





2452


2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
** not actually change anything.  The pager uses this to see if it
** should acquire the database exclusive lock prior to invoking
** the op==1 case.
*/
int sqlite3WalExclusiveMode(Wal *pWal, int op){
  int rc;
  assert( pWal->writeLock==0 );

  /* pWal->readLock is usually set, but might be -1 if there was a prior OOM */





  assert( pWal->readLock>=0 || pWal->lockError );


  if( op==0 ){
    if( pWal->exclusiveMode ){
      pWal->exclusiveMode = 0;
      if( pWal->readLock>=0 
       && walLockShared(pWal, WAL_READ_LOCK(pWal->readLock))!=SQLITE_OK
      ){
        pWal->exclusiveMode = 1;
      }
      rc = pWal->exclusiveMode==0;
    }else{
      /* Already in locking_mode=NORMAL */
      rc = 0;
    }







>
|
>
>
>
>
>

>
>



<
|
<







2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463

2464

2465
2466
2467
2468
2469
2470
2471
** not actually change anything.  The pager uses this to see if it
** should acquire the database exclusive lock prior to invoking
** the op==1 case.
*/
int sqlite3WalExclusiveMode(Wal *pWal, int op){
  int rc;
  assert( pWal->writeLock==0 );

  /* pWal->readLock is usually set, but might be -1 if there was a 
  ** prior error while attempting to acquire are read-lock. This cannot 
  ** happen if the connection is actually in exclusive mode (as no xShmLock
  ** locks are taken in this case). Nor should the pager attempt to
  ** upgrade to exclusive-mode following such an error.
  */
  assert( pWal->readLock>=0 || pWal->lockError );
  assert( pWal->readLock>=0 || (op<=0 && pWal->exclusiveMode==0) );

  if( op==0 ){
    if( pWal->exclusiveMode ){
      pWal->exclusiveMode = 0;

      if( walLockShared(pWal, WAL_READ_LOCK(pWal->readLock))!=SQLITE_OK ){

        pWal->exclusiveMode = 1;
      }
      rc = pWal->exclusiveMode==0;
    }else{
      /* Already in locking_mode=NORMAL */
      rc = 0;
    }

Changes to test/wal2.test.

417
418
419
420
421
422
423






424
425
426
427
428
429
430
...
713
714
715
716
717
718
719












































720
721
722
723
724
725
726
#
#   wal2-6.3.*: Changing back to rollback mode from WAL mode after setting 
#               locking_mode=exclusive.
#
#   wal2-6.4.*: Check that xShmLock calls are omitted in exclusive locking
#               mode.
#






do_test wal2-6.1.1 {
  file delete -force test.db test.db-wal test.db-journal
  sqlite3 db test.db
  execsql {
    Pragma Journal_Mode = Wal;
    Pragma Locking_Mode = Exclusive;
  }
................................................................................
    SELECT * FROM t2;
  }
} {normal exclusive I II III IV}
do_test wal2-6.5.3 {
  execsql { PRAGMA wal_checkpoint }
} {}
db close













































#-------------------------------------------------------------------------
# Test a theory about the checksum algorithm. Theory was false and this
# test did not provoke a bug.
#
file delete -force test.db test.db-wal test.db-journal
do_test wal2-7.1.1 {







>
>
>
>
>
>







 







>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>







417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
...
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
#
#   wal2-6.3.*: Changing back to rollback mode from WAL mode after setting 
#               locking_mode=exclusive.
#
#   wal2-6.4.*: Check that xShmLock calls are omitted in exclusive locking
#               mode.
#
#   wal2-6.5.*: 
#
#   wal2-6.6.*: Check that if the xShmLock() to reaquire a WAL read-lock when
#               exiting exclusive mode fails (i.e. SQLITE_IOERR), then the
#               connection silently remains in exclusive mode.
#
do_test wal2-6.1.1 {
  file delete -force test.db test.db-wal test.db-journal
  sqlite3 db test.db
  execsql {
    Pragma Journal_Mode = Wal;
    Pragma Locking_Mode = Exclusive;
  }
................................................................................
    SELECT * FROM t2;
  }
} {normal exclusive I II III IV}
do_test wal2-6.5.3 {
  execsql { PRAGMA wal_checkpoint }
} {}
db close

proc lock_control {method filename handle spec} {
  foreach {start n op type} $spec break
  if {$op == "lock"} { return SQLITE_IOERR }
  return SQLITE_OK
}
do_test wal2-6.6.1 {
  testvfs T
  T script lock_control
  T filter {}
  sqlite3 db test.db -vfs T
  execsql { PRAGMA locking_mode = exclusive }
  execsql { INSERT INTO t2 VALUES('V', 'VI') }
} {}
do_test wal2-6.6.2 {
  execsql { PRAGMA locking_mode = normal }
  T filter xShmLock
  execsql { INSERT INTO t2 VALUES('VII', 'VIII') }
} {}
do_test wal2-6.6.3 {
  # At this point the connection should still be in exclusive-mode, even
  # though it tried to exit exclusive-mode when committing the INSERT
  # statement above. To exit exclusive mode, SQLite has to take a read-lock 
  # on the WAL file using xShmLock(). Since that call failed, it remains
  # in exclusive mode.
  #
  sqlite3 db2 test.db -vfs T
  catchsql { SELECT * FROM t2 } db2
} {1 {database is locked}}
do_test wal2-6.6.2 {
  db2 close
  T filter {}
  execsql { INSERT INTO t2 VALUES('IX', 'X') }
} {}
do_test wal2-6.6.3 {
  # This time, we have successfully exited exclusive mode. So the second
  # connection can read the database.
  sqlite3 db2 test.db -vfs T
  catchsql { SELECT * FROM t2 } db2
} {0 {I II III IV V VI VII VIII IX X}}

db close
db2 close
T delete

#-------------------------------------------------------------------------
# Test a theory about the checksum algorithm. Theory was false and this
# test did not provoke a bug.
#
file delete -force test.db test.db-wal test.db-journal
do_test wal2-7.1.1 {