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Re: Are unreferenced TOASTed values retrieved?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: William Blunn <bill+postgresql(at)blunn(dot)org>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Are unreferenced TOASTed values retrieved?
Date: 2009-10-21 19:12:35
Message-ID: 2495.1256152355@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
William Blunn <bill+postgresql(at)blunn(dot)org> writes:
> Will the query engine retrieve the entire row (including 10 megabytes of 
> out-of-line TOASTed data) for every row, and then pick out column 
> "name", and take an age to do so,

No.  That's pretty much the whole point of the TOAST mechanism;
out-of-line values are not fetched unless actually needed.  See
http://developer.postgresql.org/pgdocs/postgres/storage-toast.html

			regards, tom lane

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