> Before going much further, I suggest that you find and read the
> section on blob filters in the doc set, and look at some of the
> sample filters in filters.c in the jrd module of the firebird code.

We didn't go the BLOB filter way because we found it to be poorly
documented and while asking for support in this group a while ago
people have indicated that BLOB filters are not the way to go.

Anyway, the solution we worked out based on UDF and a view works nice
(it really does produce the expected bitmaps) and currently only
suffers from the mentioned disadvantage. (... it suffers very much
though...)

Mirco