| From: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
|---|---|
| To: | tv(at)fuzzy(dot)cz |
| Cc: | "Davenport, Julie" <JDavenport(at)ctcd(dot)edu>, "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: query taking much longer since Postgres 8.4 upgrade |
| Date: | 2011-03-21 16:49:39 |
| Message-ID: | AANLkTimmUk2Br3C50FiFAYSAEGLamoc9tFiw8j0s+sdf@mail.gmail.com |
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| Lists: | pgsql-general |
On Mon, Mar 21, 2011 at 11:32 AM, <tv(at)fuzzy(dot)cz> wrote:
>> Incredible! Setting enable_nestloop off temporarily for the run of this
>> script made it run in less than a minute (had been running in 10 or 11
>> minutes). I think you have found a solution for many of my slow running
>> scripts that use these same type of joins. Thanks again.
>> Julie
>
> Nice. Can you post EXPLAIN ANALYZE again, so that we can see why this plan
> was evaluated as as more expensive before disabling nested loops?
well the problem is obvious -- the planner is estimating ~ 250 loops,
when it in fact has to do ~ 60k. That's a two orders of magnitude
miss.
merlin
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