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Re: [PERFORMANCE] work_mem vs temp files issue

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Jaime Casanova <jcasanov(at)systemguards(dot)com(dot)ec>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, decibel <decibel(at)decibel(dot)org>, psql performance list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: [PERFORMANCE] work_mem vs temp files issue
Date: 2010-01-11 20:18:40
Message-ID: 18803.1263241120@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Jaime Casanova <jcasanov(at)systemguards(dot)com(dot)ec> writes:
> LOG:  begin tuple sort: nkeys = 1, workMem = 1024, randomAccess = f
> LOG:  switching to bounded heapsort at 641 tuples: CPU 0.08s/0.13u sec elapsed 0.25 sec
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.5", size 471010
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.10", size 81096
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.0", size 467373
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.9", size 110200
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.3", size 470011
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.8", size 157192
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.4", size 468681
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.12", size 101624
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.1", size 472285
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.11", size 100744
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.6", size 467173
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.7", size 141888
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.2", size 476227
> LOG:  temporary file: path "base/pgsql_tmp/pgsql_tmp8507.13", size 89072
> LOG:  performsort starting: CPU 0.10s/0.19u sec elapsed 0.33 sec
> LOG:  performsort done: CPU 0.10s/0.19u sec elapsed 0.33 sec
> LOG:  internal sort ended, 118 KB used: CPU 0.10s/0.19u sec elapsed 0.33 sec

Hmm.  Not clear where the temp files are coming from, but it's *not* the
sort --- the "internal sort ended" line shows that that sort never went
to disk.  What kind of plan is feeding the sort node?

			regards, tom lane

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