[firebird-support] Composite index - issue or not existing feature?

[liviuslivius liviusliv...@poczta.onet.pl [firebird-support]]

Hi,
 
simple table
 
CREATE TABLE XXX(
A INTEGER
, B INTEGER
, CONSTRAINT UK_XXX__A__B UNIQUE(A, B)
)
commit;
 
SELECT * FROM dbo.XXX X WHERE X.A BETWEEN 2 AND 30 AND X.B BETWEEN 5 AND 60  
 
Select Expression
    -> Filter
        -> Table "XXX" as "X" Access By ID
            -> Bitmap
                -> Index "UK_XXX__A__B" Range Scan (lower bound: 1/2, upper 
bound: 1/2)
 
As you can see only A key is used but B key should be also used.
I am missing something?
Is this issue in Firebird3 or this is not existing feature?
 
AFAIK in MSSQL this work ok
 
regards,
Karol Bieniaszewski