Re: Planning large IN lists

Is this a TODO?

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Tom Lane wrote:
> Neil Conway <neilc(at)samurai(dot)com> writes:
> > When planning queries with a large IN expression in the WHERE clause,
> > the planner transforms the IN list into a scalar array expression. In
> > clause_selectivity(), we estimate the selectivity of the ScalarArrayExpr
> > by calling scalararraysel(), which in turn estimates the selectivity of
> > *each* array element in order to determine the selectivity of the array
> > expression as a whole.
>
> > This is quite inefficient when the IN list is large.
>
> That's the least of the problems. We really ought to convert such cases
> into an IN (VALUES(...)) type of query, since often repeated indexscans
> aren't the best implementation.
>
> regards, tom lane
>
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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
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