Or sub_type 5 (=SUMMARY) that in ISQL will look:

SQL> select rdb$runtime from rdb$relations where rdb$relation_id=3;
PLAN (RDB$RELATIONS INDEX (RDB$INDEX_1))
RDB$RUNTIME
=================
6:f0
==============================================================================
RDB$RUNTIME:
?RDB$INDEX_NAME?RDB$FIELD_NAME?RDB$FIELD_POSITION RDB$TRIGGER_17 RDB$TRIG
GER_18
==============================================================================

while it should be:

SQL> select rdb$runtime from rdb$relations where rdb$relation_id=3;

RDB$RUNTIME
=================
6:f0
==============================================================================
RDB$RUNTIME:
Field id: 0
name: RDB$INDEX_NAME
Field id: 1
name: RDB$FIELD_NAME
Field id: 2
name: RDB$FIELD_POSITION
trigger_name: RDB$TRIGGER_17
trigger_name: RDB$TRIGGER_18
==============================================================================

There are built in filters from 0,1,2,3,5,6,7,8 to 1.
But some are not up to date, e.g.

SQL> select rdb$runtime from rdb$relations where rdb$relation_id=142;
==================================
142 6:1ea
==================================
RDB$RUNTIME:
Field id: 0
name: ID_ICON
*** unknown verb 21 ***
Field id: 1
name: CODE_VZP
*** unknown verb 21 ***
==================================

Ivan