--- In firebird-support@yahoogroups.com, Dmitry Yemanov <dimitr@...> wrote:

>
> Actually, the real plan is the same in both v1.5 and v2.0. Versions
> prior to v2.0 simply cannot report its INDEX part, although execute it.
> The real difference is that the INDEX part seems really missing on the
> problematic host, hence the performance issue there and lack of problems
> on other v1.5 hosts. It cannot be validated visually, but symptoms speak
> for this suspicion. The possible reasons are: (1) disabled index
> BILLING_PRO_KEY or (2) outdated index statistics.
>

The index is not disabled, that was the first thing I checked. Besides, by manually forcing the plan to include the index performance returns to normal, so that would indicate that the index exists and is enabled.

I am going to try to refresh the index stats tonight, but the RDB$STATISTICS column for that index currently has a value of 4.6E-7 which I would think would be close enough to zero for all practical purposes.