SQL>analyze index index_name validate structure;

SQL> SELECT blocks, pct_used, distinct_keys
2 lf_rows, del_lf_rows
3 FROM index_stats;
BLOCKS PCT_USED LF_ROWS DEL_LF_ROWS
------ --------- -------- ------------
25 11 14 0
1 row selected.
Reorganize the index if it has a high proportion of deleted rows, for example, when the
ratio of DEL_LF_ROWS to LF_ROWS exceeds 30%.

LF_ROWS ：叶子数

DEL_LF_ROWS：删除的叶子数

要在同一个session中查看，否则看不见数据。