| From: | Robert Treat <xzilla(at)users(dot)sourceforge(dot)net> |
|---|---|
| To: | pgsql-hackers(at)postgresql(dot)org |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Subject: | Re: Index Tuning Features |
| Date: | 2006-10-10 22:56:17 |
| Message-ID: | 200610101856.17786.xzilla@users.sourceforge.net |
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| Lists: | pgsql-hackers |
On Tuesday 10 October 2006 12:06, Tom Lane wrote:
> > Similar in usage to an EXPLAIN, the RECOMMEND command would return a
> > list of indexes that need to be added to get the cheapest plan for a
> > particular query (no explain plan result though).
>
> Both of these seem to assume that EXPLAIN results, without EXPLAIN
> ANALYZE results to back them up, are sufficient for tuning. I find
> this idea a bit dubious, particularly for cases of "marginal" indexes.
>
While I agree with Tom that generally EXPLAIN is not enough for tuning, I also
know that when your dealing with queries that have run times in multiples of
hours (and the corresponding hour long index builds) EXPLAIN ANALYZE just
isn't an option. Anything that can be done to wheedle down your choices
before you have to run EXPLAIN ANALYZE is a bonus.
--
Robert Treat
Build A Brighter LAMP :: Linux Apache {middleware} PostgreSQL
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