On 18/06/2020 02:10, Dmitry Yemanov wrote: > 17.06.2020 21:34, Adriano dos Santos Fernandes wrote: >> >> So it's about this, correct? >> >> -- Uses two index segments >> select registro_sec_roest from dp_registro_oest where registro_pri_roest >> = 1 and registro_sec_roest = 1; >> >> -- Uses one index segment - more generalization of IN problem >> select registro_sec_roest from dp_registro_oest where registro_pri_roest >> = 1 and registro_sec_roest in (1, 2); >> >> -- Uses one index segment - IN problem >> select registro_sec_roest from dp_registro_oest where registro_pri_roest >> = 1 and (registro_sec_roest = 1 or registro_sec_roest is null); > > All cases use two segments. However, this: > Looks like an empty table causes different behavior for (n1 = 1 and (n2 = 2 or n2 = 3)) to ((n1 = 1 and n2 = 2) or (n1 = 1 and n2 = 3)).
I suppose something like a Conditional Bitmap may work, where T12 is index on T (N1, N2): select * from t where (n1 = 1 and (n2 = 1 or n2 is null)) or (n1 = 1 and ? is null) Select Expression -> Filter -> Table "T" Access By ID -> ***Conditional*** Bitmap Or // was Bitmap Or -> Bitmap Or -> Bitmap -> Index "T12" Range Scan (full match) -> Bitmap -> Index "T12" Range Scan (full match) -> Bitmap -> Index "T12" Range Scan (partial match: 1/2) Adriano Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
