[firebird-support] Understand query plan Filter after Filter

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

Hi,
 
what does it mean if below i have twice -> Filter -> Filter?
 
 
Select Expression
    -> Filter
        -> Nested Loop Join (outer)
            -> Filter
                -> Table "RDB$DATABASE" as "X RDB$DATABASE" Full Scan
            -> Filter
                -> Filter
                    -> Table "RDB$RELATION_FIELDS" as "RF" Access By ID
                        -> Bitmap
                            -> Index "RDB$INDEX_4" Range Scan (full match)
Select Expression
    -> Filter
        -> Nested Loop Join (outer)
            -> Filter
                -> Table "RDB$RELATIONS" as "R" Full Scan
            -> Filter
                -> Table "RDB$DATABASE" as "Y RDB$DATABASE" Full Scan
 
Karol Bieniaszewski