Re: Seqscan in MAX(index_column)

Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Neil Conway wrote:
> >> In general, I don't think this is worth doing.
>
> > It is possible it isn't worth doing. Can the INSERT/DELETE
> > incrementing/decrementing the cached count work reliabily?
>
> I don't even see how the notion of a single cached value makes
> theoretical sense, when in principle every transaction may have
> a different idea of the correct answer.
>
> You could doubtless maintain a fairly good approximate total this
> way, and that would be highly useful for some applications ...
> but it isn't COUNT(*).

With MVCC allowing multiple rows with only one visible, I thought the
INSERT/DELETE system would work --- once the delete becomes visible, the
change becomes visible.

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