From: Kevin Grittner <Kevin.Grittner@wicourts.gov>
To: Greg Stark <gsstark@mit.edu>
Cc: pgsql-performance@postgresql.org
Subject: Re: Good News re count(*) in 8.1
Date: Thu, 23 Feb 2006 12:54:52 -0600
Message-ID: <43FDB09C.EE98.0025.0@wicourts.gov> (raw)
In-Reply-To: <87irr6zq7j.fsf@stark.xeocode.com>
References: <43FC4384.EE98.0025.0@wicourts.gov>
<87irr6zq7j.fsf@stark.xeocode.com>
>>> On Wed, Feb 22, 2006 at 9:52 pm, in message
<87irr6zq7j.fsf@stark.xeocode.com>, Greg Stark <gsstark@mit.edu> wrote:
> "Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
>
>> There have been several times that I have run a SELECT COUNT(*) on
an entire
>> table on all central machines. On identical hardware, with identical
data,
>> and equivalent query loads, the PostgreSQL databases have responded
with a
>> count in 50% to 70% of the time of the commercial product, in spite
of the
>> fact that the commercial product does a scan of a non- clustered
index while
>> PostgreSQL scans the data pages.
>
> I take it these are fairly narrow rows? The big benefit of index-
only scans
> come in when you're scanning extremely wide tables, often counting
rows
> matching some indexed criteria.
I'm not sure what you would consider "fairly narrow rows" -- so see the
attached. This is the VACUUM ANALYZE VERBOSE output for the largest
table, from last night's regular maintenance run.
-Kevin
Attachments:
CaseHist-vacuum-analyze.txt (application/octet-stream, 1.5K) download
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To: pgsql-performance@postgresql.org
Cc: Kevin.Grittner@wicourts.gov, gsstark@mit.edu
Subject: Re: Good News re count(*) in 8.1
In-Reply-To: <43FDB09C.EE98.0025.0@wicourts.gov>
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