Re: Postgres optimizer choosing wrong index

From: Jack Orenstein <jack(dot)orenstein(at)hds(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Postgres optimizer choosing wrong index
Date: 2008-10-28 14:36:00
Message-ID: 49072350.3040505@hds.com
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Tom Lane wrote:
> Jack Orenstein <jack(dot)orenstein(at)hds(dot)com> writes:
>> EXPLAIN says that the correct index is being used -- it didn't used
>> to. However, pg_stat* says otherwise. In my test, I have exactly one
>> dh value. Running EXPLAIN with this value produces a plan using idx_dh
>> (the correct index), but pg_stats says that idx_dn is being used (see
>> psql session below).
>
> Yeah, if you are using cached plans (via PREPARE or plpgsql functions)
> then the plan stays the same for the life of the session ... pre 8.3
> that is.

Thank you.

One of the great things about postgres is being able to understand things all
the way down with the patient help of the actual developers.

Jack

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