Re: Slow update with simple query

Jens Schipkowski a écrit :
> On Wed, 13 Dec 2006 13:23:41 +0100, Arnaud Lesauvage <thewild@freesurf.fr>
>> Why is this query better than the other one ? Because it runs the
>> "(field IN ('some','other') AND field2 = 'Y')" once and then executes
>> the join with the resulting set ?
> True. The Subselect in FROM clause will be executed once and will be
> joined using the condition at where clause. So your condition at t2 is not
> executed for each row in t1(2mio records) but for each row in t2(1k
> records). And the boolean value is already set during update.

OK Jens, thanks for clarifying this.
I thought the planner could guess what to do in such cases.

Regards
--
Arnaud