Allow to use index when GROUP BY on field which has DESCENDING index
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Key: CORE-4529
URL: http://tracker.firebirdsql.org/browse/CORE-4529
Project: Firebird Core
Issue Type: Improvement
Reporter: Pavel Zotov
SQL> recreate table t(x int, y int); commit;
SQL> insert into t select rand()*5, rand()*5 from rdb$types, rdb$types; commit;
SQL> create DESCENDING index t_x_desc on t(x); commit;
SQL> set planonly;
SQL> select x,max(y) from t group by x;
PLAN SORT (T NATURAL) -- ? :(
SQL> select x,min(y) from t group by x;
PLAN SORT (T NATURAL) -- ? :(
SQL> set planonly;
SQL> drop index t_x_desc; commit;
---------- compare when ASC index on this field: --------
SQL> create index t_x_asc on t(x); commit;
SQL> set planonly;
SQL> select x,max(y) from t group by x;
PLAN (T ORDER T_X_ASC)
SQL> select x,min(y) from t group by x;
PLAN (T ORDER T_X_ASC)
SQL> set planonly;
SQL> drop index t_x_asc; commit;
PS. LI-T3.0.0.31288
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