5. 创建完成后分析索引
但是接下来还有一件事。创建完成后要分析索引，否则就是走了索引，查询速度也会很慢。
SQL> explain plan for select count(*) from stat_submit_center where recordtime>trunc(sysdate);
Explained.
SQL> @?/rdbms/admin/utlxplp.sql
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost | Pstart| Pstop |
-------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 9 | 4 | | |
| 1 | SORT AGGREGATE | | 1 | 9 | | | |
| 2 | PARTITION RANGE ALL | | | | | 1 | 50 |
|* 3 | INDEX FAST FULL SCAN| IDX_SUBMIT_RECORDTIME | 8878K| 76M| 4 | 1 | 50 |
-------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - filter("STAT_SUBMIT_CENTER"."RECORDTIME">TRUNC(SYSDATE@!))
Note: cpu costing is off
16 rows selected.
SQL> set autotrace on explain
SQL> set timing on
SQL> select count(*) from stat_submit_center where recordtime>trunc(sysdate);
aa^Cselect count(*) from stat_submit_center where recordtime>trunc(sysdate)
*
ERROR at line 1:
ORA-01013: user requested cancel of current operation
Elapsed: 00:11:49.85
SQL>
SQL> set autotrace off
上面可以看到，因为没有分析索引，虽然它走的是新建的IDX_SUBMIT_RECORDTIME索引，但是查询速度很慢，10分钟后也没有结果。下面我们分析一下：
SQL> Analyze index IDX_SUBMIT_RECORDTIME estimate statistics;
Index analyzed.
Elapsed: 00:00:06.84
SQL> set autotrace on explain
SQL> select count(*) from stat_submit_center where recordtime>trunc(sysdate);
COUNT(*)
----------
926736
Elapsed: 00:00:05.37
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=4360 Card=1 Bytes=9)
1 0 SORT (AGGREGATE)
2 1 PARTITION RANGE (ALL)
3 2 INDEX (RANGE SCAN) OF 'IDX_SUBMIT_RECORDTIME' (NON-UNI
QUE) (Cost=4360 Card=8878740 Bytes=79908660)
SQL> set autotrace off
索引分析之后，查询时间为5分钟左右，效率大大提高。
至此，完成全部操作。
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