Re: query produces 1 GB temp file
Tom Lane <tgl@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Greg Stark <gsstark@mit.edu>
Cc: Dirk Lutzebaeck <lutzeb@aeccom.com>, pgsql-performance@postgresql.org
Date: 2005-02-05T22:41:24Z
Lists: pgsql-performance
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