Hi, It is strange because it seems that the WAL journal mode was enabled:
Trace 1: before setting WAL mode ================= Filename: /mnt/share/testApp/myDB.db State: WRITER_CACHEMOD errCode=0 Lock: EXCLUSIVE Locking mode: locking_mode=exclusive Journal mode: journal_mode=delete Backing store: tempFile=0 memDb=0 useJournal=1 Journal: journalOff=66056 journalHdr=0 Size: dbsize=35 dbOrigSize=35 dbFileSize=35 Trace 2: after setting WAL mode ================= Filename: /mnt/share/testApp/myDB.db State: WRITER_CACHEMOD errCode=0 Lock: EXCLUSIVE Locking mode: locking_mode=exclusive Journal mode: journal_mode=wal Backing store: tempFile=0 memDb=0 useJournal=1 Journal: journalOff=66056 journalHdr=0 Size: dbsize=35 dbOrigSize=35 dbFileSize=35 So why do we have EXCLUSIVE LOCK requests on the database file? Regards, Sandu On Mon, Nov 11, 2013 at 6:33 PM, Sandu Buraga <sandu.bur...@gmail.com>wrote: > Hi, > > I took your advice and now I am setting only once the journal_mode=WAL, > also locking_mode=EXCLUSIVE and temp_store=MEMORY. But still it doesn't > work, and I get DB locks immediately. I enabled SQLite traces, and I also > added some supplementary traces when the WAL is set. Even if the > journal_mode=WAL pragma seems to be successful, I don't think that the WAL > works because I see no wal file on the disk, also I should have some WAL > related traces, which are not present. > > Below are the SQLite traces, and it can be seen that 3.x locking model it > is used, instead of WAL. Somewhere a thread tries to get a READ SHARED > lock, but on the database there is already an EXCLUSIVE lock. Normally this > should not occur, because the reader should be able to use the database and > WAL file. The auto-checkpoint for the WAL failed is 1000 pages, so it > should not be immediately. > > > OPENX 11 /mnt/share/testApp/myDB.db 0402 > fcntl unknown pid=233565 tid=20 11 1 0 > fcntl unknown pid=233565 tid=20 11 2 0 > OPEN 11 /mnt/share/testApp/myDB.db > OPEN 139631224 /mnt/share/testApp/myDB.db > OPEN 139631856 /mnt/share/testApp/myDB.db > OPENX 12 /mnt/share/testApp/myDB.db 02 > fcntl unknown pid=233565 tid=20 12 1 0 > fcntl unknown pid=233565 tid=20 12 2 0 > OPEN 12 /mnt/share/testApp/myDB.db > OPEN 139746432 /mnt/share/testApp/myDB.db > OPEN 139627904 /mnt/share/testApp/myDB.db > OPENX 13 /mnt/share/testApp/myDB.db 02 > fcntl unknown pid=233565 tid=20 13 1 0 > fcntl unknown pid=233565 tid=20 13 2 0 > OPEN 13 /mnt/share/testApp/myDB.db > OPEN 139547936 /mnt/share/testApp/myDB.db > OPEN 139811888 /mnt/share/testApp/myDB.db > OPENX 14 /mnt/share/testApp/myDB.db 02 > fcntl unknown pid=233565 tid=20 14 1 0 > fcntl unknown pid=233565 tid=20 14 2 0 > OPEN 14 /mnt/share/testApp/myDB.db > OPEN 139943040 /mnt/share/testApp/myDB.db > OPEN 139544616 /mnt/share/testApp/myDB.db > OPENX 15 /mnt/share/testApp/myDB.db 02 > fcntl unknown pid=233565 tid=20 15 1 0 > fcntl unknown pid=233565 tid=20 15 2 0 > OPEN 15 /mnt/share/testApp/myDB.db > OPEN 139585952 /mnt/share/testApp/myDB.db > OPEN 139586584 /mnt/share/testApp/myDB.db > LOCK 11 SHARED was NONE(NONE,0) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741824 1 125195948 0 > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741826 510 125195948 0 > fcntl pid=233565 tid=20 11 SETLK UNLCK 1073741824 1 125195948 0 > LOCK 11 SHARED ok (unix) > UNLOCK 11 0 was 1(1,1) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK UNLCK 0 0 138882344 0 > CLOSE 139631224 > UNLOCK 11 0 was 0(0,0) pid=233565 tid=20 (unix) > CLOSE -1 > OPENX 11 /mnt/share/testApp/myDB.db 0402 > fcntl unknown pid=233565 tid=20 11 1 0 > fcntl unknown pid=233565 tid=20 11 2 0 > OPEN 11 /mnt/share/testApp/myDB.db > LOCK 11 SHARED was NONE(NONE,0) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741824 1 138848960 0 > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741826 510 138848960 0 > fcntl pid=233565 tid=20 11 SETLK UNLCK 1073741824 1 138848960 0 > LOCK 11 SHARED ok (unix) > UNLOCK 11 0 was 1(1,1) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK UNLCK 0 0 1 0 > LOCK 11 SHARED was NONE(NONE,0) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741824 1 125196700 0 > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741826 510 125196700 0 > fcntl pid=233565 tid=20 11 SETLK UNLCK 1073741824 1 125196700 0 > LOCK 11 SHARED ok (unix) > UNLOCK 11 0 was 1(1,1) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK UNLCK 0 0 2 0 > LOCK 11 SHARED was NONE(NONE,0) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741824 1 125196428 0 > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741826 510 125196428 0 > fcntl pid=233565 tid=20 11 SETLK UNLCK 1073741824 1 125196428 0 > LOCK 11 SHARED ok (unix) > UNLOCK 11 0 was 1(1,1) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK UNLCK 0 0 2 0 > LOCK 11 SHARED was NONE(NONE,0) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741824 1 125195612 0 > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741826 510 125195612 0 > fcntl pid=233565 tid=20 11 SETLK UNLCK 1073741824 1 125195612 0 > LOCK 11 SHARED ok (unix) > LOCK 11 RESERVED was SHARED(SHARED,1) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK WRLCK 1073741825 1 125195676 0 > LOCK 11 RESERVED ok (unix) > TRANSACTION 139631856 > OPENX 16 /mnt/share/testApp/myDB.nal 0402 > fcntl unknown pid=233565 tid=20 16 1 0 > fcntl unknown pid=233565 tid=20 16 2 0 > OPEN 16 /mnt/share/testApp/myDB.nal > WRITE 16 512 0 0 > APPEND 139631856 page 1 needSync=1 > APPEND 139631856 page 1 needSync=1 > APPEND 139631856 page 1 needSync=1 > APPEND 139631856 page 1 needSync=1 > APPEND 139631856 page 2 needSync=1 > APPEND 139631856 page 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needSync=1 > APPEND 139631856 page 1 needSync=1 > APPEND 139631856 page 1 needSync=1 > APPEND 139631856 page 1 needSync=1 > APPEND 139631856 page 35 needSync=1 > APPEND 139631856 page 1 needSync=1 > APPEND 139631856 page 1 needSync=1 > LOCK 11 EXCLUSIVE was RESERVED(RESERVED,1) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK WRLCK 1073741824 1 125195660 0 > fcntl pid=233565 tid=20 11 SETLK WRLCK 1073741826 510 125195660 0 > LOCK 11 EXCLUSIVE ok (unix) > DATABASE SYNC: File=/mnt/share/testApp/myDB.db zMaster= nSize=35 > APPEND 139631856 page 1 needSync=1 > READ 16 0 512 0 > SYNC journal of 139631856 > SYNC 16 > DIRSYNC /mnt/share/testApp/myDB.nal (have_fullfsync=0 fullsync=0) > fcntl unknown pid=233565 tid=20 17 1 0 > fcntl unknown pid=233565 tid=20 17 2 0 > OPENDIR 17 /mnt/share/testApp > WRITE 16 12 0 0 > SYNC journal of 139631856 > SYNC 16 > READ 11 0 24 0 > WRITE 11 65536 0 0 > STORE 139631856 page 1 hash(00000000) > WRITE 11 65536 65536 0 > STORE 139631856 page 2 hash(00000000) > WRITE 11 65536 131072 0 > STORE 139631856 page 3 hash(00000000) > WRITE 11 65536 196608 0 > STORE 139631856 page 4 hash(00000000) > WRITE 11 65536 262144 0 > STORE 139631856 page 5 hash(00000000) > WRITE 11 65536 327680 0 > STORE 139631856 page 6 hash(00000000) > WRITE 11 65536 393216 0 > STORE 139631856 page 7 hash(00000000) > WRITE 11 65536 458752 0 > STORE 139631856 page 8 hash(00000000) > WRITE 11 65536 524288 0 > STORE 139631856 page 9 hash(00000000) > WRITE 11 65536 589824 0 > STORE 139631856 page 10 hash(00000000) > WRITE 11 65536 655360 0 > STORE 139631856 page 11 hash(00000000) > WRITE 11 65536 720896 0 > STORE 139631856 page 12 hash(00000000) > WRITE 11 65536 786432 0 > STORE 139631856 page 13 hash(00000000) > WRITE 11 65536 851968 0 > STORE 139631856 page 14 hash(00000000) > WRITE 11 65536 917504 0 > STORE 139631856 page 15 hash(00000000) > WRITE 11 65536 983040 0 > STORE 139631856 page 16 hash(00000000) > WRITE 11 65536 1048576 0 > STORE 139631856 page 17 hash(00000000) > WRITE 11 65536 1114112 0 > STORE 139631856 page 18 hash(00000000) > WRITE 11 65536 1179648 0 > STORE 139631856 page 19 hash(00000000) > WRITE 11 65536 1245184 0 > STORE 139631856 page 20 hash(00000000) > WRITE 11 65536 1310720 0 > STORE 139631856 page 21 hash(00000000) > WRITE 11 65536 1376256 0 > STORE 139631856 page 22 hash(00000000) > WRITE 11 65536 1441792 0 > STORE 139631856 page 23 hash(00000000) > WRITE 11 65536 1507328 0 > STORE 139631856 page 24 hash(00000000) > WRITE 11 65536 1572864 0 > STORE 139631856 page 25 hash(00000000) > WRITE 11 65536 1638400 0 > STORE 139631856 page 26 hash(00000000) > WRITE 11 65536 1703936 0 > STORE 139631856 page 27 hash(00000000) > WRITE 11 65536 1769472 0 > STORE 139631856 page 28 hash(00000000) > WRITE 11 65536 1835008 0 > STORE 139631856 page 29 hash(00000000) > WRITE 11 65536 1900544 0 > STORE 139631856 page 30 hash(00000000) > WRITE 11 65536 1966080 0 > STORE 139631856 page 31 hash(00000000) > WRITE 11 65536 2031616 0 > STORE 139631856 page 32 hash(00000000) > WRITE 11 65536 2097152 0 > STORE 139631856 page 33 hash(00000000) > WRITE 11 65536 2162688 0 > STORE 139631856 page 34 hash(00000000) > WRITE 11 65536 2228224 0 > STORE 139631856 page 35 hash(00000000) > SYNC 11 > COMMIT 139631856 > CLOSE -1 > UNLOCK 11 1 was 4(4,1) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741826 510 125195724 0 > fcntl pid=233565 tid=20 11 SETLK UNLCK 1073741824 2 125195724 0 > UNLOCK 11 0 was 1(1,1) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK UNLCK 0 0 125195676 0 > LOCK 11 SHARED was NONE(NONE,0) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741824 1 125195868 0 > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741826 510 125195868 0 > fcntl pid=233565 tid=20 11 SETLK UNLCK 1073741824 1 125195868 0 > LOCK 11 SHARED ok (unix) > READ 11 16 24 0 > UNLOCK 11 0 was 1(1,1) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK UNLCK 0 0 125195980 0 > OPEN 139523248 > TRANSACTION 139523248 > APPEND 139523248 page 1 needSync=1 > APPEND 139523248 page 1 needSync=1 > APPEND 139523248 page 1 needSync=1 > APPEND 139523248 page 1 needSync=1 > APPEND 139523248 page 2 needSync=1 > APPEND 139523248 page 1 needSync=1 > APPEND 139523248 page 1 needSync=1 > APPEND 139523248 page 1 needSync=1 > APPEND 139523248 page 1 needSync=1 > DATABASE SYNC: File= zMaster= nSize=2 > COMMIT 139523248 > JOURNALMODE new : 5, old : 0 > JOURNALMODE_WAL will be enabled > 27 1 0 > Temp file /mnt/share/testApp/myDB.db Shared memory support 1 > LOCK 11 SHARED was NONE(NONE,0) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741824 1 125195932 0 > fcntl pid=233565 tid=20 11 SETLK RDLCK 1073741826 510 125195932 0 > fcntl pid=233565 tid=20 11 SETLK UNLCK 1073741824 1 125195932 0 > LOCK 11 SHARED ok (unix) > READ 11 16 24 0 > LOCK 11 RESERVED was SHARED(SHARED,1) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK WRLCK 1073741825 1 125195996 0 > LOCK 11 RESERVED ok (unix) > LOCK 11 EXCLUSIVE was RESERVED(RESERVED,1) pid=233565 tid=20 (unix) > fcntl pid=233565 tid=20 11 SETLK WRLCK 1073741824 1 125195964 0 > fcntl pid=233565 tid=20 11 SETLK WRLCK 1073741826 510 125195964 0 > LOCK 11 EXCLUSIVE ok (unix) > TRANSACTION 139631856 > OPENX 16 /mnt/share/testApp/myDB.nal 0402 > fcntl unknown pid=233565 tid=20 16 1 0 > fcntl unknown pid=233565 tid=20 16 2 0 > OPEN 16 /mnt/share/testApp/myDB.nal > WRITE 16 512 0 0 > WRITE 16 4 512 0 > WRITE 16 65536 516 0 > WRITE 16 4 66052 0 > JOURNAL 139631856 page 1 needSync=1 hash(00000000) > DATABASE SYNC: File=/mnt/share/testApp/myDB.db zMaster= nSize=35 > READ 16 0 66560 0 > SYNC journal of 139631856 > SYNC 16 > DIRSYNC /mnt/share/testApp/myDB.nal (have_fullfsync=0 fullsync=0) > fcntl unknown pid=233565 tid=20 17 1 0 > fcntl unknown pid=233565 tid=20 17 2 0 > OPENDIR 17 /mnt/share/testApp > WRITE 16 12 0 0 > SYNC journal of 139631856 > SYNC 16 > READ 11 4 24 0 > WRITE 11 65536 0 0 > STORE 139631856 page 1 hash(00000000) > SYNC 11 > COMMIT 139631856 > CLOSE -1 > LOCK 13 SHARED was NONE(EXCLUSIVE,1) pid=233565 tid=16 (unix) > LOCK 13 SHARED failed (unix) > UNLOCK 13 0 was 0(4,1) pid=233565 tid=16 (unix) > ROLLBACK 139547936 > LOCK 13 SHARED was NONE(EXCLUSIVE,1) pid=233565 tid=20 (unix) > LOCK 13 SHARED failed (unix) > UNLOCK 13 0 was 0(4,1) pid=233565 tid=20 (unix) > ROLLBACK 139547936 > LOCK 13 SHARED was NONE(EXCLUSIVE,1) pid=233565 tid=20 (unix) > LOCK 13 SHARED failed (unix) > UNLOCK 13 0 was 0(4,1) pid=233565 tid=20 (unix) > ROLLBACK 139547936 > LOCK 13 SHARED was NONE(EXCLUSIVE,1) pid=233565 tid=20 (unix) > LOCK 13 SHARED failed (unix) > UNLOCK 13 0 was 0(4,1) pid=233565 tid=20 (unix) > ROLLBACK 139547936 > LOCK 13 SHARED was NONE(EXCLUSIVE,1) pid=233565 tid=20 (unix) > LOCK 13 SHARED failed (unix) > UNLOCK 13 0 was 0(4,1) pid=233565 tid=20 (unix) > ROLLBACK 139547936 > > > Regards, > Sandu Buraga > > > > Date: Thu, 31 Oct 2013 14:05:17 -0400 > From: Richard Hipp <d...@sqlite.org> > To: General Discussion of SQLite Database <sqlite-users@sqlite.org> > Subject: Re: [sqlite] Enable WAL on a QNX system > Message-ID: > <CALwJ= > mxoxoqd7jyd68l3o7ajpqsil40mrrxm4saiv9rpdkc...@mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > On Thu, Oct 31, 2013 at 9:56 AM, Sandu Buraga <sandu.bur...@gmail.com > >wrote: > > > Hi, > > > > I am using SQLite 3.7.9, and QNX 6.5.0 running on Intel x86 machine. I > am > > having a use-case with multiple readers threads and one writer thread, > all > > running in the same process. No other process is using the SQLite > database > > file. > > > > I tried to enable WAL feature, but with no success so far. Each thread > has > > it's own handle: > > > > res = sqlite3_open_v2( m_FilePath.getBuffer(), &dbHandle, > > > > SQLITE_OPEN_READWRITE|SQLITE_ > OPEN_WAL|SQLITE_OPEN_FULLMUTEX|SQLITE_OPEN_PRIVATECACHE, > > NULL ); > > > > immediately after I am making these PRAGMA statements for the new opened > > handle > > > > "PRAGMA main.journal_mode=WAL;" > > "PRAGMA temp_store=MEMORY;" > > > > So if I have 5 threads, I am calling the above sequence 5 times for each > > distinct handle > > > > (1) WAL mode is a persistent property of the database file. Set it once > from a single-threaded connection and it will stay set forever. You should > not try to set WAL mode on each connection separately. > > (2) WAL mode uses mmap() to get access to a small piece of memory that is > shared between all connections. But the mmap() is unreliable on many > version so QNX. If you must use WAL mode, first run "PRAGMA > locking_mode=EXCLUSIVE". That will prevent all processes but the first > from connecting to the database (though many threads from within that one > process can have their own individual connections). And since only a > single process is accessing the database, heap memory instead of mmap() > memory is used for the shared memory region. This trick enables WAL mode > to work reliably on QNX. > > > > > > > When the code is executed I am getting frequently "databed locked" > > messages. I tried to diagnose the issue, by enabling also the WAL traces > in > > the SQLite amalgamation, but I noticed no message, so for me it looks > like > > the WAL feature was not enabled. By analyzing the existed traces it looks > > like thread 2 - reader is getting a SHARED lock, while later process 3 - > > writer is trying to get an EXCLUSIVE lock. > > > > Any suggestion would be appreciated. > > > > Regards, > > Sandu > > _______________________________________________ > > sqlite-users mailing list > > sqlite-users@sqlite.org > > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > > > > > > -- > D. Richard Hipp > d...@sqlite.org > _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
