Appendix D. System Tables - D.20 RDB$INDEX_SEGMENTS - 《Firebird 4.0 Language Reference》

D.20 RDB$INDEX_SEGMENTS

D.20 `RDB$INDEX_SEGMENTS`

RDB$INDEX_SEGMENTS stores the segments (table columns) of indexes and their positions in the key. A separate row is stored for each column in an index.

Column Name	Data Type	Description
`RDB$INDEX_NAME`	`CHAR(63)`	The name of the index this segment is related to. The master record is `RDB$INDICES.RDB$INDEX_NAME`.
`RDB$FIELD_NAME`	`CHAR(63)`	The name of a column belonging to the index, corresponding to an identifier for the table and that column in `RDB$RELATION_FIELDS.RDB$FIELD_NAME`
`RDB$FIELD_POSITION`	`SMALLINT`	The column position in the index. Positions are numbered left-to-right, starting at zero
`RDB$STATISTICS`	`DOUBLE PRECISION`	The last known (calculated) selectivity of this column in the index. The higher the number, the lower the selectivity.