Ed, Dan opened a ticket. I agree the documentation isn't clear on the Exlusive locking state.
Not really sure, if this is by design or a bug at this stage. I do think its a great feature of the Shared cache mode to allow table level locking. But I'm curious with this table level locking what would happen if two threads performed writes to two seperate tables concurrently using only a begin immediate. Thread a writes to tab1, Thread b writes to tab2, (Is this allowed ? or is a sqlite_locked kicked returned?) If it is allowed then would there be two journal files concurrently existing? And What happens during a crash with two journals ? This gets complicated very quickly. Ken Ed Pasma <[EMAIL PROTECTED]> wrote: Hello,` Empirically I found that it is exactly true. Must admit I'm confused but may it is in line with the Shared-Cache locking model. This does not mention the EXCLUSIVE locking state. The most 'secure' locking state it mentions is a write-transaction and this can coexist with read-transactions from others. Thus "begin exclusive" starts a write-transaction and the on-going read does not interfere. The error message seems to clarify the situation further: database table is locked. Thus the collision occurs at the table-level. And yes, taking different tables for read and write, it does not occur. Practically this may not help very much. But may be the following does in case you have a busy_timeout setting. When having Shared-Cache mode enabled, the timeout setting appears to be ignored by SQLite. This makes locking situations surface rather soon, also when there is no dead-lock. The situation may be handled by a programmatic retry? Regards, Ed Op 19-dec-2007, om 19:12 heeft Ken het volgende geschreven: > Some additional info: > > when the sqlite_lock is returned there is another thread that > appears to be reading the same table. Does the sqlite3 step return > sqlite_locked in this case? > > Thanks, > Ken > > > Ken wrote: > While using the new 3.5.4 sqlite3_enable_shared_cache I ran into a > strange lock situation. > > SQLITE_LOCK is returned from an insert statement, even though > the thread/connection performed a successful "begin exclusive" > transaction. > > begin exclusive > insert into table... ---> returns SQLITE_LOCKED > > Is it possible for both connections to begin exclusive transactions > whilst having the shared cache anabled? > > Thanks, > ken > > ----------------------------------------------------------------------------- To unsubscribe, send email to [EMAIL PROTECTED] -----------------------------------------------------------------------------
