From: Gregory Stark <stark@enterprisedb.com>
To: Karl Wright <kwright@metacarta.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: Performance query about large tables, lots of concurrent access
Date: Tue, 19 Jun 2007 16:46:20 +0100
Message-ID: <873b0o7xrn.fsf@oxford.xeocode.com> (raw)
In-Reply-To: <4677ECA9.3000402@metacarta.com>
References: <4676DD57.7070304@metacarta.com>
<14291.1182221811@sss.pgh.pa.us>
<4677B831.8060704@metacarta.com>
<27690.1182263794@sss.pgh.pa.us>
<4677ECA9.3000402@metacarta.com>
"Karl Wright" <kwright@metacarta.com> writes:
>> In this case it looks like the planner is afraid that that's exactly
>> what will happen --- a cost of 14177 suggests that several thousand row
>> fetches are expected to happen, and yet it's only predicting 5 rows out
>> after the filter. It's using this plan anyway because it has no better
>> alternative, but you should think about whether a different index
>> definition would help.
Another index won't help if the reason the cost is so high isn't because the
index isn't very selective but because there are lots of dead tuples.
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
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To: pgsql-performance@postgresql.org
Cc: stark@enterprisedb.com, kwright@metacarta.com, tgl@sss.pgh.pa.us
Subject: Re: Performance query about large tables, lots of concurrent access
In-Reply-To: <873b0o7xrn.fsf@oxford.xeocode.com>
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