Statistics automatically gathered on indexes?

Question

I haven't paid much attention to this in the past, but I notice in XE that user_indexes
is automatically populated when you create an index - num_rows, last_analyzed,
etc. I suppose the simple act of creating the index collects enough data to
provide those statistics, and Oracle uses them instead of throwing them away.
Below is output from a simple script run in XE creating a table and four indexes.
user_indexes.last_analyzed is not null even without any explicit
gathering of statistics. num_rows, etc. are all populated...
This does NOT happen in Enterprise 9.2.0.4...
SQL> drop table pkt2;
Table dropped.
SQL> create table pkt2 as
2 select rownum row_num, rownum / object_id not_row_num, 2 * rownum / object_id not_row_num2
3 from all_objects
4 /
Table created.
SQL>
SQL> select table_name, last_analyzed from user_tables where table_name = 'PKT2';
TABLE_NAME LAST_ANAL
PKT2
SQL> create unique index pkt2_1_udx on pkt2(row_num);
Index created.
SQL> create index pkt2_2_idx on pkt2(not_row_num);
Index created.
SQL> create index pkt2_3_idx on pkt2(row_num, not_row_num);
Index created.
SQL> create index pkt2_4_idx on pkt2(row_num, not_row_num, not_row_num2);
Index created.
SQL> select index_name, last_analyzed, num_rows, leaf_blocks, clustering_factor
2 from user_indexes where table_name = 'PKT2';
INDEX_NAME LAST_ANAL NUM_ROWS LEAF_BLOCKS CLUSTERING_FACTOR
PKT2_3_IDX 27-NOV-05 4794 25 36
PKT2_4_IDX 27-NOV-05 4794 40 36
PKT2_1_UDX 27-NOV-05 4794 10 36
PKT2_2_IDX 27-NOV-05 4794 23 2322

Answer 1

that is normal behaviour in 10g