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List:       postgresql-sql
Subject:    Re: [SQL] materialize
From:       Tom Lane <tgl () sss ! pgh ! pa ! us>
Date:       2007-11-26 21:53:45
Message-ID: 4140.1196114025 () sss ! pgh ! pa ! us
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Ehab Galal <ehabgalal123@hotmail.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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