From: Tom Lane <tgl@sss.pgh.pa.us>
To: Craig James <craig_james@emolecules.com>
Cc: valiouk@yahoo.co.uk, psql performance <pgsql-performance@postgresql.org>
Subject: Re: Perl/DBI vs Native
Date: Mon, 21 Jul 2008 14:44:32 -0400
Message-ID: <16163.1216665872@sss.pgh.pa.us> (raw)
In-Reply-To: <4884C633.5050506@emolecules.com>
References: <768129.60859.qm@web25802.mail.ukl.yahoo.com>
<4884C633.5050506@emolecules.com>
Craig James <craig_james@emolecules.com> writes:
> Valentin Bogdanov wrote:
>> I have ran quite a few tests comparing how long a query takes to
>> execute from Perl/DBI as compared to psql/pqlib. No matter how many
>> times I run the test the results were always the same.
>>
>> I run a SELECT all on a fairly big table and enabled the
>> log_min_duration_statement option. With psql postgres consistently
>> logs half a second while the exact same query executed with Perl/DBI
>> takes again consistently 2 seconds.
> The problem may be that your two tests are not equivalent. When Perl
> executes a statement, it copies the *entire* result set back to the
> client before it returns the first row.
Sure, but so does psql (unless you've turned on the magic FETCH_COUNT
setting). I think the theories about prepared versus literal statements
were more promising; but I don't know DBI well enough to know exactly
what it was sending to the server.
regards, tom lane
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, craig_james@emolecules.com
Subject: Re: Perl/DBI vs Native
In-Reply-To: <16163.1216665872@sss.pgh.pa.us>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox