Re: So, is COUNT(*) fast now?

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От Tom Lane
Тема Re: So, is COUNT(*) fast now?
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Msg-id 20908.1319339688@sss.pgh.pa.us
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Ответ на Re: So, is COUNT(*) fast now?  (Robert Haas <robertmhaas@gmail.com>)
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Robert Haas <robertmhaas@gmail.com> writes:
> On Fri, Oct 21, 2011 at 3:55 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Robert Haas <robertmhaas@gmail.com> writes:
>>> Anyhow, here's the scoop.  On my desktop machine running F14, running
>>> SELECT sum(1) FROM pgbench_accounts in a tight loop, 60 s worth of
>>> oprofile data:
>>> 176830   13.0801  postgres                 postgres                 ExecProject

>> Hm, that's weird.  In both these cases, I'd have expected that
>> ExecProject would get optimized away thanks to selection of a physical
>> tlist for the scan node.  Wonder if that got broken ...

> If it did, it looks like it wasn't recent.  I set up the same test
> case on my MacBook using REL9_1_STABLE and REL9_0_STABLE and set a
> breakpoint on ExecProject().  Both back-branches appear to also call
> ExecProject() for every tuple.

Oh, the ExecProject calls are coming from advance_aggregates().
Move along, nothing to see here ...
        regards, tom lane


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