Re: Slow query after upgrade to 8.4 - Mailing list pgsql-performance

From Robert Haas
Subject Re: Slow query after upgrade to 8.4
Date
Msg-id 603c8f070909271145s39eac057r78b5a1b62599c372@mail.gmail.com
Whole thread Raw
In response to Re: Slow query after upgrade to 8.4  (Jared Beck <jared@singlebrook.com>)
List pgsql-performance
On Thu, Sep 24, 2009 at 8:22 AM, Jared Beck <jared@singlebrook.com> wrote:
> Should we try to improve statistics collection for that column
> (variableid) by using ALTER TABLE ... ALTER COLUMN ... SET STATISTICS?

It's worth a try, but I'm not sure it's going to help much.  The LIKE
condition is hard for the planner to estimate at present.

>  In other words, if the row estimate were perfect would we be likely
> to get a better plan?  Or is that impossible to speculate on?

Good row estimates are the key to happiness, but I don't know whether
it will actually change the plan in this instance.

> Thanks again.  Already you've been a big help.  We love postgres and
> are very happy with our upgrade to 8.4 so far!

Glad to hear it.

...Robert

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