Is this a TODO?


Tom Lane wrote:
> Neil Conway <[EMAIL PROTECTED]> 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
> ---------------------------(end of broadcast)---------------------------
> TIP 7: You can help support the PostgreSQL project by donating at

  Bruce Momjian  <[EMAIL PROTECTED]>

  + If your life is a hard drive, Christ can be your backup. +

---------------------------(end of broadcast)---------------------------
TIP 3: Have you checked our extensive FAQ?


Reply via email to