Dan Kennedy <danielk1977-re5jqeeqqe8avxtiumw...@public.gmane.org> writes:
> On Aug 17, 2010, at 1:48 AM, Nikolaus Rath wrote:
>
>> Hello,
>>
>> The script below fails with
>>
>> Deadlock detected when executing 'DELETE FROM foo WHERE id=2'
>>
>> What I think should be happening instead is this:
>>
>> - When executing statement 1, the main thread obtains a SHARED lock.
>
>> - When executing statement 2, the main thread briefly obtains an
>> EXCLUSIVE lock. After statement 2 is executed, the EXCLUSIVE lock is
>> released and the main thread continues to hold the SHARED lock
>> (since
>> statement 1 is still active)
>
> Quite correct.
Hmm. That's quite the opposite of what Igor said in his mail. Who is
right now?
>> - Thread 2 wants to get an EXCLUSIVE lock but it can't. So the busy
>> handlers waits for the main thread to release it's lock.
>
> While waiting, thread 2 is holding a PENDING lock.
Is there any way to convince thread 2 not to hold the pending lock while
waiting? I tried to disable setbusytimeout() and do a manual wait as
follows (in void execute()):
rc=sqlite3_prepare_v2(db, s, -1, &stmt, NULL);
assert(rc==SQLITE_OK);
rc=sqlite3_step(stmt);
if (rc == SQLITE_BUSY) {
printf("Busy, retrying '%s'\n", s);
rc=sqlite3_finalize(stmt);
if(rc!=SQLITE_OK){
printf("Error finalizing '%s': %s\n", s, sqlite3_errmsg(db));
exit(1);
}
sleep(2);
rc=sqlite3_prepare_v2(db, s, -1, &stmt, NULL);
assert(rc==SQLITE_OK);
rc=sqlite3_step(stmt);
}
but now I'm getting an error when finalizing the statement:
Busy, retrying 'UPDATE foo SET id=42 WHERE id=5'
Error finalizing 'UPDATE foo SET id=42 WHERE id=5': database is locked
On the other hand, if I do not finalize the statement but just wait for
2 seconds before calling sqlite3_step() again, I get the same error as
before (so I reasoned that to get rid of the PENDING lock I have to
finalize the statement).
Best,
-Nikolaus
--
»Time flies like an arrow, fruit flies like a Banana.«
PGP fingerprint: 5B93 61F8 4EA2 E279 ABF6 02CF A9AD B7F8 AE4E 425C
_______________________________________________
sqlite-users mailing list
sqlite-users@sqlite.org
http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
