From: Tom Lane <tgl@sss.pgh.pa.us>
To: Craig A. James <cjames@modgraph-usa.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: explain analyze reports 20x more time than actual
Date: Fri, 30 Jun 2006 02:04:49 -0400
Message-ID: <20524.1151647489@sss.pgh.pa.us> (raw)
In-Reply-To: <44A4AE1A.4070308@modgraph-usa.com>
References: <448C505C.2080504@modgraph-usa.com>
<87ac8jfu7t.fsf@stark.xeocode.com>
<448E5A92.9050206@modgraph-usa.com>
<22609.1150209419@sss.pgh.pa.us>
<44A4AE1A.4070308@modgraph-usa.com>
"Craig A. James" <cjames@modgraph-usa.com> writes:
> I have a query that needs to run faster, with the obvious solution
> being to add an index. But to confirm this, I ran explain analyze.
> When I run the actual query, it consistently takes 6-7 seconds by the
> wall clock. My application with a "verbose" mode enabled reports 6.6
> seconds consistently. However, when I run EXPLAIN ANALYZE, it takes
> 120 seconds!
See recent discussions --- if you've got duff PC hardware, it seems that
reading the clock takes forever :-(. In this case I'd assume that the
cost of the seqscan (11497361 rows returned) is being overstated because
of the 2*11497361 gettimeofday calls involved.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, cjames@modgraph-usa.com
Subject: Re: explain analyze reports 20x more time than actual
In-Reply-To: <20524.1151647489@sss.pgh.pa.us>
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