Re: why does count take so long?

How about keeping counts of inserts, deletes and updates per table per
transaction as part of the live statistics?

Tom Lane wrote:
>
> I said:
> > Greg Stark <gsstark(at)mit(dot)edu> writes:
> >> Things like count(*) could use int4 until it overflows though.
>
> > I don't see a reasonable way for an aggregate to change state datatype
> > on the fly; otherwise this would be a great solution.
>
> On the other hand, the cost is imposed by the generic aggregate
> definition that says the aggregate state transition function is an
> ordinary function. This is fine for user-defined aggregates, but there
> is no law that says that all the built-in aggregates must use that same
> API. We could probably invent some API that allows COUNT(*) to keep its
> running count someplace where it needn't be re-palloc'd on every cycle.
> Something to think about for 7.5 (too late for 7.4 I fear).
>
> regards, tom lane
>
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