On 19 Mar 2014 at 12:45, Simon Slavin <slav...@bigfraud.org> wrote:
> On 19 Mar 2014, at 11:21am, Tim Streater <t...@clothears.org.uk> wrote:
>
>> So I could do: $dbh = new sqlite3 ($dbname, SQLITE_OPEN_READONLY); ??
>
> Yes. I think that's the way you're meant to do it if you really do want
> readonly.
>
>> 3) Is the lock always released if I do $dbh->close(); ?
>>
>>> No longer need to answer this, but it brings up the fact that, if you
>>> haven't
>>> already released the lock by closing all the transactions on the database,
>>> the
>>> ->close() will fail because you have unfinished work. So that's another
>>> reason to be fussy about using transactions correctly.
>>
>> So suppose I have this sequence (ignoring any error handling for clarity):
>>
>> $dbh = new sqlite3 ($database);
>> $res = $dbh->query ('select ...');
>>
>> while (true)
>> {
>> $reg = $res->fetchArray (SQLITE3_ASSOC);
>> if ($reg===false) break;
>> // Do stuff with this row of results - may take some minutes
>> $dbh->exec ('update ...');
>> // Do more stuff - may take some minutes
>> $dbh->exec ('update ...');
>> }
>>
>> $res->finalize ();
>> $dbh->close ();
>>
>> then is the locking issue not so much the distance between the "new" and the
>> dbclose, as the distance between the query and its finalize() ? If this is
>> the case then I can simply gather the results I need from the select and do
>> the time-consuming loop as a separate step.
>
> Correct. While your query is running (until you have finalized or reset it)
> you have a lock on the database.
Thanks - that's clarified it properly. Means I can fix it more simply, and
without lots of opens/closes.
--
Cheers -- Tim
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