From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
Cc: | Martijn van Oosterhout <kleptog(at)svana(dot)org>, Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: WITH RECUSIVE patches 0723 |
Date: | 2008-07-28 23:18:14 |
Message-ID: | 395.1217287094@sss.pgh.pa.us |
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Lists: | pgsql-hackers pgsql-patches |
Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> Tom Lane wrote:
>> My thought is that we could optimize away materialization in cases where
>> we can tell it's not needed (no volatile functions and/or no multiple
>> scans of the subquery). But not being able to do it means we've
>> implemented the feature incorrectly.
> I'm not sure how much work that would involve, but none of this means we
> can't have the feature for 8.4, right? Just that there is more work to do.
I would be *extremely* surprised if we don't find ourselves improving
the optimization of WITH clauses long after 8.4. We're still working on
outer joins, remember ;-). My point here is just that the base case
before optimization has to behave per spec. Optimizing more later is
good, fixing deliberately introduced non-compliance not so good.
regards, tom lane
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