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Re: Why performance improvement on converting subselect

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Rajesh Kumar Mallah <mallah(at)trade-india(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Why performance improvement on converting subselect
Date: 2003-07-31 03:21:38
Message-ID: 27221.1059621698@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Rajesh Kumar Mallah <mallah(at)trade-india(dot)com> writes:
> Below are the plans for two cases. I dont know how to read them accurately
> can u please explain them.

Well, they're the same plan, as far as they go.  I suppose that the
runtime difference must come from choosing a different plan inside the
most_recent_edition() function, which we cannot see in the explain
output.  As before, turning on logging of verbose query plans is the
only way to look at what the function is doing.

> Also can anyone point to some documentation
> oriented towards understanding explain analyze output?

http://www.postgresql.org/docs/view.php?version=7.3&idoc=0&file=performance-tips.html

			regards, tom lane

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