> Would collecting table statistics not enough?

If the default value of the CASCADE parameter is TRUE, executing GATHER_TABLE_STATS gathers the statistics for both the table and the index. Hence, it might be enough. Be careful, however, that also partition-level statistics are re-gathered. So, it depends what do you want to achieve and how much time you have to do it…

HTH
Chris

I know this is an old post but I was wondering if we really need to manually gather global level index statistics. Would collecting table statistics not enough?

sql> CREATE TABLE t5 (n1 number, n2 number)
2 PARTITION BY RANGE (n1) (
3 PARTITION p1 VALUES LESS THAN (11),
4 PARTITION p2 VALUES LESS THAN (21)
5 );

Table created.

sql>> INSERT INTO t5
2 SELECT rownum, rownum
3 FROM dual
4 connect by level commit;

Commit complete.

sql> CREATE INDEX i ON t5 (n2) LOCAL;

Index created.

sql> SELECT partition_name, global_stats, distinct_keys
2 FROM user_ind_statistics
3 WHERE index_name = ‘I’;

PARTITION_NAME GLO DISTINCT_KEYS
—————————— — ————-
NO 10
P1 NO 10
P2 NO 10

sql> exec dbms_stats.gather_table_stats(user, ‘T5′);

PL/SQL procedure successfully completed.

sql>> SELECT partition_name, global_stats, distinct_keys
2 FROM user_ind_statistics
3 WHERE index_name = ‘I’;

PARTITION_NAME GLO DISTINCT_KEYS
—————————— — ————-
YES 20
P1 YES 10
P2 YES 10

Best regards

Mohamed Houri