Horton

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

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@postgresql.org
Date: 2011-10-21T19:52:46Z
Lists: pgsql-hackers

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  1. Remove pg_upgrade dependency on the 'postgres' database existing in the

On Fri, Oct 21, 2011 at 3:07 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> [ oprofile results ]

*grovels through the line-by-line results*

Hmm, I guess there is a bit of a hotspot in StoreIndexTuple, which is
probably being folded into IndexOnlyNext in the per-function timings:

    ExecClearTuple(slot);
    for (i = 0; i < nindexatts; i++)
        values[i] = index_getattr(itup, i + 1, itupdesc, &isnull[i]);
    ExecStoreVirtualTuple(slot);

If I'm reading these results right, that section is about 3% of the
total number of samples.

Also, this line is kind of expensive:

        if (!visibilitymap_test(scandesc->heapRelation,
                                ItemPointerGetBlockNumber(tid),
                                &node->ioss_VMBuffer))

Around 2%.  But I don't see any way to avoid that, or even make it cheaper.

-- 
Robert Haas
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