Stephan Szabo wrote:
>
>
> I think you'd want to move the entire query excepting the lastml where
> condition into a single subselect in the outer from with the lastml
> condition on the outside:
> select * from (<old query minus lastml condition>) as blah where
> lastml=2;
>
> However, I don't think this changes the computation that it's doing
> (simple example explains still show two subquery runs).
>
Yep, that works. I wasn't familiar with how the subselect in the from part works.
But as
you say an explain still shows it doing the index scan twice.
From the postgres docs:
A sub-SELECT can appear in the FROM clause. This acts as though its output were
created as a temporary table for the duration of this single SELECT command. Note that
the
sub-SELECT must be surrounded by parentheses, and an alias must be provided for it.
So does postgres actually use a temporary table behind the scenses? It appears not.
--
Joseph Shraibman
[EMAIL PROTECTED]
Increase signal to noise ratio. http://www.targabot.com
---------------------------(end of broadcast)---------------------------
TIP 6: Have you searched our list archives?
http://www.postgresql.org/search.mpl
