Re: why does count take so long?

Is improving count(*) <a lot if possible> on one of the TODO lists?

Jean-Luc Lachance wrote:

>How about keeping counts of inserts, deletes and updates per table per
>transaction as part of the live statistics?
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>Tom Lane wrote:
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>>I said:
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>>>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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