Submitted by: Reginald Poyau (rpoyau)

Is related to CORE4927

How to reproduce:
1> run isql
> create table test1 (id integer not null primary key, tms timestamp default current_timestamp);
> create table test2 (id integer not null primary key, tms timestamp default current_timestamp);
> alter table test1 add occurred integer computed by (case when tms < current_timestamp then 1 else 0 end);
> create index test1_idx0 on test1 computed by (case when tms < current_timestamp then 1 else 0 end);
> alter table test2 add occurred integer;
> create index test2_idx0 on test2(occurred);
> insert into test1(id) values(1);
> insert into test2(id) values(1);
> commit;
> set plan;
select * from test1 where occurred = 1;

PLAN (TEST1 INDEX (TEST1_IDX0))
> select * from test2 where occurred = 1;

PLAN (TEST2 INDEX (TEST2_IDX0))
> select * from (select * from test1 union select * from test2) where occurred = 1;

PLAN (TEST1 NATURAL)
PLAN (TEST2 INDEX (TEST2_IDX0))

      ID         TMS     OCCURRED

============ =========== ============
1 18-SEP-2015 1

> commit;
> create view test_view as select * from test1 union select * from test2;
> select * from test_view where occurred = 1;

PLAN (TEST_VIEW TEST1 NATURAL)
PLAN (TEST_VIEW TEST2 INDEX (TEST2_IDX0))

      ID         TMS     OCCURRED

============ =========== ============
1 18-SEP-2015 1
>

Notice that subselect on union on test1 and test2 index TEST1_IDX0 did not get used.
Notice that select test_view also did not use TEST1_IDX0 index.

Commits: 6e50d9b FirebirdSQL/fbt-repository@395f5be