Charles H. Woloszynski wrote:
>
>
> Richard Huxton wrote:
>
> >Depends on usage patterns and how you build your application. There are a
> >couple of oddities with workarounds: count() and max() aren't very optimised
> >for example.
> >
> You can 'fix' the max() SNAFU with a new query of the form
> "select field from tbl limit 1 order by field desc" (not precise
> syntax, but the idea is correct)
>
> I call it a SNAFU since it I hate to have to change queries from
> something obvious to a more obscure format just to work around
> an optimizer issue.
>
> Not sure if there is an equivalent query to make count() work
> faster
The problem with optimizing COUNT() is that different backends have
different tuple views, meaning the count from one backend could be
different than from another backend. I can't see how to optimize that.
Does oracle do it? Maybe by looking their redo segements. We don't
have those because redo is stored in the main table.
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
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