Re: [GENERAL] I feel the need for speed. What am I doing wrong?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: johnnnnnn <john(at)phaedrusdeinus(dot)org>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: [GENERAL] I feel the need for speed. What am I doing wrong?
Date: 2003-01-08 04:07:35
Message-ID: 645.1041998855@sss.pgh.pa.us
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johnnnnnn <john(at)phaedrusdeinus(dot)org> writes:
> On Tue, Jan 07, 2003 at 03:10:06PM -0800, Dann Corbit wrote:
>> -> Seq Scan on CNX_DS_53_SIS_STU_OPT_FEE_TB a
>> (cost=100000000.00..100112549.62 rows=6139062 width=24)

> Those big round numbers suggest that you haven't run vacuum analyze on
> all of your tables.

No; the 100000000.00 is a tipoff that he's set enable_seqscan off, but
the system is using a seqscan anyway because it cannot find any other
plan.

"SET enable_seqscan = off" does not prevent the planner from generating
seqscan plans, it just adds 100000000.00 to the cost estimate. That
will generally cause the planner to pick another plan --- if it can find
one. In this case it evidently cannot find any indexscan alternative.

regards, tom lane

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