Re: [HACKERS] Slow count(*) again...

On Thu, Feb 03, 2011 at 12:44:23PM -0500, Chris Browne wrote:
> mladen(dot)gogala(at)vmsinfo(dot)com (Mladen Gogala) writes:
> > Hints are not even that complicated to program. The SQL parser should
> > compile the list of hints into a table and optimizer should check
> > whether any of the applicable access methods exist in the table. If it
> > does - use it. If not, ignore it. This looks to me like a
> > philosophical issue, not a programming issue.
>
> It's worth looking back to what has already been elaborated on in the
> ToDo.
>
> http://wiki.postgresql.org/wiki/Todo
> -----------------------------------
> Optimizer hints (not wanted)
>
> Optimizer hints are used to work around problems in the optimizer and
> introduce upgrade and maintenance issues. We would rather have the
> problems reported and fixed. We have discussed a more sophisticated
> system of per-class cost adjustment instead, but a specification remains
> to be developed.

And as to the 'wait around for a new version to fix that': there are
constantly excellent examples of exactly this happening, all the time
with PostgreSQL - most recent example I've seen -
http://archives.postgresql.org/pgsql-performance/2011-01/msg00337.php

The wait often isn't long, at all.

Ross
--
Ross Reedstrom, Ph.D. reedstrm(at)rice(dot)edu
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