Hi Richard, Yes, only one thread is working on the database first time. So even if I am opening more handles, I work only with one of the handles to run some PRAGMA statements and to check the structural integrity of database. If tables, or columns are missing I will run some DROP TABLE IF EXISTS statements, and CREATE TABLE within a transaction. The pseudo-code would be:
1. open 1 handle 2. on handle 1 - perform one SQL SELECT statement 3. on handle 1 - start a transaction and create some tables 4.a. On handle 1 - PRAGMA temp_store=MEMORY 4.b. On handle 1 - PRAGMA locking_mode=EXCLUSIVE 4.c. On handle 1 - PRAGMA main.journal_mode=WAL 5. open another 4 db connections If step 4 would be executed before step 2, I have immediately after BEGIN TRANSACTION a database lock. But, after I enable the WAL mode the consequent transactions (in any other threads) will go in database lock. I can include the SQLite traces. The code used to open the the database is: int res = sqlite3_open_v2( m_FilePath.getBuffer(), &dbHandle, SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_WAL|SQLITE_OPEN_FULLMUTEX|SQLITE_OPEN_PRIVATECACHE, NULL ); and for the next four handles: res = sqlite3_open_v2( m_FilePath.getBuffer(), &secondaryDbHandle, SQLITE_OPEN_READWRITE|SQLITE_OPEN_FULLMUTEX|SQLITE_OPEN_PRIVATECACHE, NULL ); Regards, Sandu Buraga >> On Mon, Nov 11, 2013 at 12:33 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. >>> >> >> There can only be a single connection open on the database file when you >> change it to WAL mode. Did you try to change to WAL mode while holding >> multiple connections open? >> >> >The above is not quite correct. >There can be multiple connections open, but none of the other connections >can have any kind of lock. Are you sure that you don't have another thread >trying to read the database file when you enter WAL mode? The easiest way >to ensure this is to put the database in WAL mode when the first thread >connects, and before any other threads have even opened. _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
