Subject Re: [firebird-support] Query optimization help
Author Kjell Rilbe
Aage Johansen wrote:

> Kjell Rilbe wrote:
> > As I understand it, the problem is that it will repeat the subquery for
> > each record in the outer query and that the low index selectivity of the
> > subquery indices causes these subqueries to execute rather sluggishly.
> Maybe not quite. I think Fb is waisting time on indexes which add less
> than nothing to performance.

Couldn't Firebird be made to detect this problem automatically? Or
perhaps the way it evaluates index statistics could be adjusted to
reduce that the risk of this occurring. It does happen in too many
situations as it is now. It wouldn't be a big problem if it rarely
happened, but now I seem to run into it on some 10-50% of all queries I
create. I don't know about you, but I personally don't think that's good

Kjell Rilbe
Adressmarknaden AM AB
E-post: kjell.rilbe@...
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