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Re: XMLPARSE() evaluated multiple times?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Tim Landscheidt <tim(at)tim-landscheidt(dot)de>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: XMLPARSE() evaluated multiple times?
Date: 2009-07-20 19:54:03
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Tim Landscheidt <tim(at)tim-landscheidt(dot)de> writes:
> It seems that XMLPARSE() is called for every row without
> PostgreSQL realizing that it is IMMUTABLE.

Indeed, the system doesn't consider it immutable.  None of the examples
you show would benefit if it did, though.

I believe there are GUC-parameter dependencies that prevent us from
treating it as truly immutable, but if you want to ignore that
consideration and force constant-folding anyway, you could wrap it
in a SQL function that's marked as IMMUTABLE.

			regards, tom lane

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