我执行execute dbms_stats.gather_table_stats(ownname => 'ACMS',tabname => 'NEW_CDR' ,estimate_percent => null ,method_opt => 'for all columns' ,cascade => true);
得到的结果是
SQL> SELECT INDEX_NAME, NUM_ROWS, SAMPLE_SIZE, DISTINCT_KEYS FROM USER_INDEXES WHERE TABLE_NAME = 'NEW_CDR';
INDEX_NAME
NUM_ROWS SAMPLE_SIZE DISTINCT_KEYS
------------------------------ ---------- ----------- -------------
NEW_CDR_INDEX_CDB
2760084 2784231 2775593
SYS_C003585_1
2703117485340 2703117
10 rows selected.
SQL>SELECT COUNT(DISTINCT ID)FROM new_cdr;
COUNT(DISTINCTID)
-----------------
2784316
ID为主键,从结果看,主键上的索引是使用的估算,而我使用的compute,不是estimate
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