>> First thing I would try, _especially_ since you use inner joins, would
>> be changing the order of the tables: Instead of
>> SELECT a.id, b.id FROM a JOIN b WHERE ...
>> try
>> SELECT a.id, b.id FROM b JOIN a WHERE ...
>
>
> The order of tables in an inner join is not significant to the
> Firebird optimizer.

That may be so in theory, but in practice it _is_ significant.

>> Second thing, it's been my experience that inner joins tend to be much
>> slower than outer joins with Firebird (probably a problem with my
>> optimizations, but the end result is that I am getting much better
>> performance from SELECT a.id, b.id FROM a LEFT JOIN b WHERE ... than
>> from SELECT a.id, b.id FROM a JOIN b WHERE ...
>
> You really ought to look at the plans and the index statistics.
> What your seeing is not normal.

Again, it may not be normal in theory, but it is common in practice.
Sure, plans are the problem, but every time I checked them, they seemed
quite reasonable.

> My recollection is that an outer join with conditions on both
> tables is turned into an inner join.

Again, maybe. But it still tends to improve the performance a lot.

Pepak