From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Greco <David_Greco@harte-hanks.com>
Cc: Andrew Dunstan <andrew@dunslane.net>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: SOLVED - RE: Poor performance using CTE
Date: Wed, 14 Nov 2012 11:29:03 -0500
Message-ID: <20462.1352910543@sss.pgh.pa.us> (raw)
In-Reply-To: <187F6C10D2931A4386EE8E58E13857F61291D897@BY2PRD0811MB415.namprd08.prod.outlook.com>
References: <187F6C10D2931A4386EE8E58E13857F61291D897@BY2PRD0811MB415.namprd08.prod.outlook.com>
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
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, David_Greco@harte-hanks.com, andrew@dunslane.net
Subject: Re: SOLVED - RE: Poor performance using CTE
In-Reply-To: <20462.1352910543@sss.pgh.pa.us>
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