Re: materialize

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Ehab Galal <ehabgalal123(at)hotmail(dot)com>
Cc: "pgsql-sql(at)postgresql(dot)org" <pgsql-sql(at)postgresql(dot)org>
Subject: Re: materialize
Date: 2007-11-26 21:53:45
Message-ID: 4140.1196114025@sss.pgh.pa.us
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Ehab Galal <ehabgalal123(at)hotmail(dot)com> writes:
> I was wondering why do we need the Materialize node in the plan below when i explain a query?

It's cheaper to scan a materialized rowset many times than a raw table
--- we don't need to re-access shared memory nor re-check row visibility.

regards, tom lane

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