From: | "Julian Scarfe" <julian(at)avbrief(dot)com> |
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To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | <pgsql-sql(at)postgresql(dot)org> |
Subject: | Re: Ordering in an aggregate -- points to paths |
Date: | 2003-06-15 16:48:40 |
Message-ID: | 039401c3335d$f94d1760$0600a8c0@Wilbur |
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Lists: | pgsql-sql |
From: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
> Yeah, this is a fairly obvious thing to want to do with a user-written
> aggregate. It does not work in released versions, because the planner
> does not notice that the inner SELECT's output ordering matches what
> the GROUP BY needs, and so it inserts an additional Sort plan step
> above the sub-select (you can see this if you look at EXPLAIN output).
> Unfortunately, on most platforms qsort() isn't stable and will not
> preserve the ordering of its input for equal keys. So you lose the
> minor ordering by seq_no in the re-sort.
Most grateful for the rapid response Tom. Knowing that, I can work around by
iterating through the firs at the application level.
Regards
Julian Scarfe
PS: you shouldn't be working on a Sunday, it's bad for you ;-)
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