From: Tom Lane <tgl@sss.pgh.pa.us>
To: Adnan DURSUN <a_dursun@hotmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Why does not perform index combination
Date: Thu, 16 Feb 2006 12:27:36 -0500
Message-ID: <29367.1140110856@sss.pgh.pa.us> (raw)
In-Reply-To: <BAY106-DAV1906100D639F6AE4BBA692FAFB0@phx.gbl>
References: <BAY106-DAV1906100D639F6AE4BBA692FAFB0@phx.gbl>
"Adnan DURSUN" <a_dursun@hotmail.com> writes:
> I have query for a report. Explain analyze result is below. The =
> execution plan tells that it would use "t_koltuk_islem_pkey" index on =
> table "t_koltuk_islem" to scan. However, there is another index on table =
> "t_koltuk_islem" on column "islem_tarihi" that can be combined on plan. =
> Why doesn't optimizer choice that ? It prefer to perform a filter on =
> column "islem_tarihi" ... Why ?
Probably thinks that the extra index doesn't add enough selectivity to
be worth scanning. It's probably right, too --- maybe with a narrower
date range the answer would be different.
I think the main problem in this plan is the poor estimation of the size
of the d1/s join. Are your stats up to date on those tables? Maybe
boosting the statistics target for one or both would help.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, a_dursun@hotmail.com
Subject: Re: Why does not perform index combination
In-Reply-To: <29367.1140110856@sss.pgh.pa.us>
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