>take longer than 5 seconds. These reads are being done by PHP using the
>PDO driver for sqlite3. My understanding of the problem is that the PHP
>reader is holding a SHARED lock for longer than 5 seconds, so while the
>C program can acquire a PENDING lock, it can not get the EXCLUSIVE lock
>inside of 5 seconds and thus times out.
I've also used the PDO driver in the past and it took me a while to realise
that the SHARED lock was not being released by PDO/SQlite under after it
tried to retrieve the next row and failed. So in the following example loop:
(Run SQL select statement)
while (fetchArray())
{
/* Long time spent processing here */
}
The SHARED lock is held until the end of the while loop instead of releasing
before the loop (which I was expecting). Obviously if you have a significant
amount of processing in the loop, its not difficult to get writer
starvation.
A question to those who know - when (in terms of which C API call) does
SQLite release the SHARED lock after a read?
And a general survey to everyone... in your applications, what is the
'standard' practice to handle a SELECT statement that may return more than a
few rows? Can temporary tables be used without still holding the
database-level lock?
Sorry Mark, I've noticed I've diverged from your question a tad.
Thanks
Nick
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