Selecting from FMIOI - performance question

[Former Member]

When I select from FMIOI using one fund (FONDS) and one fund center (FISTL) (let's call it fund center 1), I get results very quickly (within seconds). If I use the same fund and a different fund center (let's call it fund center 2), I still get results back quickly. But if I use the same fund as above and both fund centers 1 and 2 as selection criteria, it takes a long time to get results back. I see this behavior in both my custom program and when using SE16. Can anyone explain why selecting from FMIOI with two fund centers causes such a performance problem when individually the fund centers return with no problem?

[Former Member]

I can't prove it, but my best guess is that the database optimizer gets confused. And unfortunately it doesn't take much either as you have seen yourself. I have seen the same behaviour with other tables, where selection_time(1) + selection_time(2) << selection_time(1+2).

The database could perform one selection, then the next one, take a coffee break, and still return results much quicker than it does when selecting for both criteria.

[KjetilKilhavn]

I can't prove it, but my best guess is that the database optimizer gets confused. And unfortunately it doesn't take much either as you have seen yourself. I have seen the same behaviour with other tables, where selection_time(1) + selection_time(2) << selection_time(1+2).

The database could perform one selection, then the next one, take a coffee break, and still return results much quicker than it does when selecting for both criteria.