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From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Greco <David_Greco@harte-hanks.com>
cc: Andrew Dunstan <andrew@dunslane.net>,
	"pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: SOLVED - RE: Poor performance using CTE
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Comments: In-reply-to David Greco <David_Greco@harte-hanks.com>
	message dated "Wed, 14 Nov 2012 16:18:42 +0000"
Date: Wed, 14 Nov 2012 11:29:03 -0500
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David Greco <David_Greco@harte-hanks.com> writes:
> Thanks, that did the trick. Though I'm still not clear as to why. 

PG treats WITH as an optimization fence --- the WITH query will be
executed pretty much as-is.  It may be that Oracle flattens the query
somehow; though if you're using black-box functions in both cases,
it's not obvious where the optimizer could get any purchase that way.

			regards, tom lane