From: Scott Marlowe <scott.marlowe@gmail.com>
To: Laurent Raufaste <analogue@glop.org>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: PG planning randomly ?
Date: Tue, 26 Feb 2008 14:06:24 -0600
Message-ID: <dcc563d10802261206i641a68f1w8719d42233dd489a@mail.gmail.com> (raw)
In-Reply-To: <669dc9710802260912y7fe58f9epe42fe7eb360119d8@mail.gmail.com>
References: <669dc9710802260719h61d846b3hd50b7f547bcb82c3@mail.gmail.com>
<3637.1204043502@sss.pgh.pa.us>
<669dc9710802260912y7fe58f9epe42fe7eb360119d8@mail.gmail.com>
On Tue, Feb 26, 2008 at 11:12 AM, Laurent Raufaste <analogue@glop.org> wrote:
> 2008/2/26, Tom Lane <tgl@sss.pgh.pa.us>:
>
> >
> > What PG version is this?
> >
> > If it's 8.2 or later then increasing the stats target for _comment.path
> > to 100 or more would likely help.
> >
>
> I'm using PG 8.2.4.
> We are using 100 as default_statistics_target by default and all our
> column are using this value:
> # SELECT attname,attstattarget FROM pg_attribute WHERE attrelid=16743
> AND attname='path' ;
> attname | attstattarget
> ---------+---------------
> path | -1
>
> I tried increasing the stats target with the command:
> SET default_statistics_target=1000 ;
> That's the command I launched before executing the ANALYZE showed in
> the previous mail.
> The ANALYZE were longer to complete, but it did not change the planner
> behavior (sometimes right, sometimes wrong).
You're doing it wrong. The default target affects newly created
columns / tables. You need to use alter table to change a stats
target after creation. Like so:
alter table abc alter column xyz set statistics 100;
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To: pgsql-performance@postgresql.org
Cc: scott.marlowe@gmail.com, analogue@glop.org, tgl@sss.pgh.pa.us
Subject: Re: PG planning randomly ?
In-Reply-To: <dcc563d10802261206i641a68f1w8719d42233dd489a@mail.gmail.com>
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