From: Tom Lane <tgl@sss.pgh.pa.us>
To: Greg Stark <gsstark@mit.edu>
Cc: Dirk Lutzebaeck <lutzeb@aeccom.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: query produces 1 GB temp file
Date: Sat, 05 Feb 2005 17:41:24 -0500
Message-ID: <29929.1107643284@sss.pgh.pa.us> (raw)
In-Reply-To: <87y8e2kb8j.fsf@stark.xeocode.com>
References: <20050205182117.0125074@mail2.aeccom.com>
<87y8e2kb8j.fsf@stark.xeocode.com>
Greg Stark <gsstark@mit.edu> writes:
> Dirk Lutzebaeck <lutzeb@aeccom.com> writes:
>> Can some please explain why the temp file is so huge? I understand
>> there are a lot of rows.
> Well that I can't explain. 22k rows of width 1361 doesn't sound so big to me
> either.
It was 700k rows to sort, not 22k. The Unique/Limit superstructure
only demanded 22k rows out from the sort, but we still had to sort 'em
all to figure out which ones were the first 22k.
> The temporary table does need to store three copies of the records at
> a given time, but still it sounds like an awful lot.
Huh?
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, gsstark@mit.edu, lutzeb@aeccom.com
Subject: Re: query produces 1 GB temp file
In-Reply-To: <29929.1107643284@sss.pgh.pa.us>
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