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Re: Help interpreting explain analyze output

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Ole Tange <postgresql(dot)org(at)tange(dot)dk>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Help interpreting explain analyze output
Date: 2004-08-15 18:13:39
Message-ID: 28313.1092593619@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Ole Tange <postgresql(dot)org(at)tange(dot)dk> writes:
> As I read it the output tells me what was done during the milliseconds:

No, you have a fundamental misconception here.  The notation means that
the first output row from a plan step was delivered after X
milliseconds, and the last row after Y milliseconds.

The "gap" you are looking at is the time to do the Sort (since a sort
can't deliver the first output row until it's finished the sort).

It is gonna take a while to sort 175000 rows ... but possibly increasing
sort_mem would help.

			regards, tom lane

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