利用ordered hints优化SQL

SQL_ID  4g70n3k9bqc5v, child number 0
-------------------------------------
MERGE INTO YJBZH_GRXDFHZMXJL GRXDFHZMXJL USING ( SELECT A.AGMT_ID AS
AGMT_ID, B.CUST_NAME AS CUST_NAME FROM DWF.F_AGT_CADB_BOOK_H A,
DWF.F_AGT_SAVB_BASICINFO_H B WHERE A.START_DT <= TO_DATE(:B1
,'yyyy-mm-dd') AND A.END_DT > TO_DATE(:B1 ,'yyyy-mm-dd') AND B.START_DT
<= TO_DATE(:B1 ,'yyyy-mm-dd') AND B.END_DT > TO_DATE(:B1 ,'yyyy-mm-dd')
AND A.MASTER_CARD_NO = B.AGMT_ID ) SAVB_BASICINFO ON (
RTRIM(GRXDFHZMXJL.DFZH) = SAVB_BASICINFO.AGMT_ID AND CJRQ =
TO_CHAR(TO_DATE(:B1 , 'YYYY-MM-DD'),'yyyymmdd') ) WHEN MATCHED THEN
UPDATE SET GRXDFHZMXJL.DFHM = SAVB_BASICINFO.CUST_NAME
 
Plan hash value: 2923259190
 
---------------------------------------------------------------------------------------------------------
| Id  | Operation                      | Name                   | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------------------------
|   0 | MERGE STATEMENT                |                        |       |       | 44331 (100)|          |
|   1 |  MERGE                         | YJBZH_GRXDFHZMXJL      |       |       |            |          |
|   2 |   VIEW                         |                        |       |       |            |          |
|   3 |    NESTED LOOPS                |                        |     1 |  1862 | 44331   (1)| 00:08:52 |
|   4 |     NESTED LOOPS               |                        |    15 |  1862 | 44331   (1)| 00:08:52 |
|   5 |      MERGE JOIN CARTESIAN      |                        |     1 |  1808 | 44313   (1)| 00:08:52 |
|*  6 |       TABLE ACCESS FULL        | YJBZH_GRXDFHZMXJL      |     1 |  1762 | 26057   (1)| 00:05:13 |
|   7 |       BUFFER SORT              |                        |  2120K|    93M| 18256   (2)| 00:03:40 |
|*  8 |        TABLE ACCESS FULL       | F_AGT_SAVB_BASICINFO_H |  2120K|    93M| 18256   (2)| 00:03:40 |
|*  9 |      INDEX RANGE SCAN          | F_AGT_CADB_BOOK_H_IDX2 |    15 |       |     2   (0)| 00:00:01 |
|* 10 |     TABLE ACCESS BY INDEX ROWID| F_AGT_CADB_BOOK_H      |     1 |    54 |    18   (0)| 00:00:01 |
---------------------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   6 - filter("CJRQ"=TO_CHAR(TO_DATE(:B1,'YYYY-MM-DD'),'yyyymmdd'))
   8 - filter(("B"."START_DT"<=TO_DATE(:B1,'yyyy-mm-dd') AND
              "B"."END_DT">TO_DATE(:B1,'yyyy-mm-dd')))
   9 - access("A"."AGMT_ID"=RTRIM("GRXDFHZMXJL"."DFZH") AND
              "A"."END_DT">TO_DATE(:B1,'yyyy-mm-dd') AND "A"."END_DT" IS NOT NULL)
  10 - filter(("A"."MASTER_CARD_NO" IS NOT NULL AND "A"."START_DT"<=TO_DATE(:B1,'yyyy-mm-dd')
              AND "A"."MASTER_CARD_NO"="B"."AGMT_ID"))
 select count(*) from YJBZH_GRXDFHZMXJL
--0
 后来发现多个merge在一个会话里,添加日志后表数据有20W+
 select count(*) from dwf.F_AGT_SAVB_BASICINFO_H B where (("B"."START_DT"<=TO_DATE(20131231,'yyyy-mm-dd') AND
              "B"."END_DT">TO_DATE(20131231,'yyyy-mm-dd')))
 ---返回了1071795条记录

那此时ID=5 就傻逼了,实际需要至少返回1071795 然后作为驱动集去驱动ID=9 那么F_AGT_CADB_BOOK_H_IDX2 需要扫描1071795次,此时SQL肯定跑不出来

这时候关联顺序变成了YJBZH_GRXDFHZMXJL和F_AGT_SAVB_BASICINFO_H进行笛卡尔积,产生的结果集在和F_AGT_CADB_BOOK_H进行关联,但是看SQL并不是这样

正确的关联顺序是F_AGT_CADB_BOOK_H和F_AGT_SAVB_BASICINFO_H关联产生的结果集在和YJBZH_GRXDFHZMXJL关联。
添加hints:
ORDERED提示强制Oracle按照From子句中表出现的顺序进行表连接。

     通过ORDERED提示，可以避免CBO SQL解析过程中的表连接评估，从而避免Oracle产生错误的执行计划，或者强制Oracle按照我们指定的方式执行。在很多时候，当我们清楚地了解数据结构和数据分布之后，就可以通过ORDERED提示来提高SQL性能。

SQL_ID  cw628tpmjcbjv, child number 0
-------------------------------------
MERGE /*+ordered*/ INTO YJBZH_GRXDFHZMXJL GRXDFHZMXJL USING ( SELECT
A.AGMT_ID AS AGMT_ID, B.CUST_NAME AS CUST_NAME FROM
DWF.F_AGT_CADB_BOOK_H A, DWF.F_AGT_SAVB_BASICINFO_H B WHERE A.START_DT
<= TO_DATE(:B1 ,'yyyy-mm-dd') AND A.END_DT > TO_DATE(:B1 ,'yyyy-mm-dd')
AND B.START_DT <= TO_DATE(:B1 ,'yyyy-mm-dd') AND B.END_DT > TO_DATE(:B1
,'yyyy-mm-dd') AND A.MASTER_CARD_NO = B.AGMT_ID ) SAVB_BASICINFO ON (
RTRIM(GRXDFHZMXJL.DFZH) = SAVB_BASICINFO.AGMT_ID AND CJRQ =
TO_CHAR(TO_DATE(:B1 , 'YYYY-MM-DD'),'yyyymmdd') ) WHEN MATCHED THEN
UPDATE SET GRXDFHZMXJL.DFHM = SAVB_BASICINFO.CUST_NAME
 
Plan hash value: 2400855618
 
--------------------------------------------------------------------------------------------------------
| Id  | Operation             | Name                   | Rows  | Bytes |TempSpc| Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------------------------
|   0 | MERGE STATEMENT       |                        |       |       |       |   138K(100)|          |
|   1 |  MERGE                | YJBZH_GRXDFHZMXJL      |       |       |       |            |          |
|   2 |   VIEW                |                        |       |       |       |            |          |
|*  3 |    HASH JOIN          |                        |     1 |  1862 |       |   138K  (2)| 00:27:39 |
|*  4 |     TABLE ACCESS FULL | YJBZH_GRXDFHZMXJL      |     1 |  1762 |       | 26057   (1)| 00:05:13 |
|*  5 |     HASH JOIN         |                        |    11M|  1074M|   374M|   112K  (2)| 00:22:25 |
|*  6 |      TABLE ACCESS FULL| F_AGT_CADB_BOOK_H      |  5951K|   306M|       | 69245   (2)| 00:13:51 |
|*  7 |      TABLE ACCESS FULL| F_AGT_SAVB_BASICINFO_H |  2120K|    93M|       | 18256   (2)| 00:03:40 |
--------------------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   3 - access("A"."AGMT_ID"=RTRIM("GRXDFHZMXJL"."DFZH"))
   4 - filter("CJRQ"=TO_CHAR(TO_DATE(:B1,'YYYY-MM-DD'),'yyyymmdd'))
   5 - access("A"."MASTER_CARD_NO"="B"."AGMT_ID")
   6 - filter(("A"."MASTER_CARD_NO" IS NOT NULL AND "A"."START_DT"<=TO_DATE(:B1,'yyyy-mm-dd')
              AND "A"."END_DT">TO_DATE(:B1,'yyyy-mm-dd')))
   7 - filter(("B"."START_DT"<=TO_DATE(:B1,'yyyy-mm-dd') AND
              "B"."END_DT">TO_DATE(:B1,'yyyy-mm-dd')))