Re: Slow query to get last created row using CURRVAL

On Sat, Dec 4, 2010 at 1:35 PM, Marti Raudsepp <marti(at)juffo(dot)org> wrote:
> On Sat, Dec 4, 2010 at 13:56, Mathieu De Zutter <mathieu(at)dezutter(dot)org> wrote:
>> I have no idea why in some cases the index scan is not considered.
>> Does anyone have an idea?
>
> I guess that it's because the currval() function is volatile -- its
> value has to be tested for again each row.
>
> Try this instead:
> SELECT user_id FROM log_event WHERE id = (SELECT CURRVAL('log_event_id_seq'));
>
> This will assure that there's only one call to currval().

OK, that makes a lot of sense. Your suggestion solves my problem.

Thanks!

Mathieu