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Re: SELECT performance problem

From: "Dave Dutcher" <dave(at)tridecap(dot)com>
To: "'Glenn Sullivan'" <glenn(dot)sullivan(at)varianinc(dot)com>,<pgsql-performance(at)postgresql(dot)org>
Subject: Re: SELECT performance problem
Date: 2007-02-20 23:46:56
Message-ID: 002701c75549$680881b0$8300a8c0@tridecap.com (view raw or flat)
Thread:
Lists: pgsql-performance
Did you run ANALYZE on your data after importing it into 8.2.3?  Is there an
index on the seqfil column?  If so, you should post the output of EXPLAIN
ANALYZE from both systems if possible.


> -----Original Message-----
> From: pgsql-performance-owner(at)postgresql(dot)org 
> [mailto:pgsql-performance-owner(at)postgresql(dot)org] On Behalf Of 
> Glenn Sullivan
> Sent: Tuesday, February 20, 2007 5:22 PM
> To: pgsql-performance(at)postgresql(dot)org
> Subject: [PERFORM] SELECT performance problem
> 
> 
> I am updating from 7.4.5 to 8.2.3.  I have noticed a significant
> slowdown in simple searches such as
>      "select filename from vnmr_data where seqfil = 'sems';"
> This returns 12 rows out of 1 million items in the table.
> On 7.4.5, this takes about 1.5 seconds.  On 8.2.3, it is taking
> about 9 seconds.
> 
> I have played with different values of:
> work_mem, temp_buffers, shared_buffers and effective_cache_size
> and none of them make any difference.
> 
> I am running on redhat Linux 4   64bit.
> 
> Any ideas?
> 
> Glenn
> 
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