rownum导致sql不能进行谓词推入

背景

案件(13405_RI-再保结算查询导出太慢)，造成性能慢的原因是执行以下sql时，每次执行平均需要消耗2秒，

画面上，点击一次导出按钮，就会发起数以百记的调用。

SQL执行代码段

select * from t_policy_payment_writeoff where policysn = 'PB12345';

t_policy_payment_writeoff为视图，其代码为：

create or replace view t_policy_payment_writeoff as
select rownum as id, t."WRITEOFFAMOUT",t."POLICYSN"
 from (
select sum(b.realamount) writeoffamout, b.custseq policysn
        --保费回写视图
          from ciod_bp.mm_writeoutstatus_to a, ciod_bp.mm_writeout_to b
         where a.id = b.id
           and a.datasource = 'RI'
           and a.status = '99'
           and a.writeouttype = '1' --回写成功的..
         group by b.custseq
 union all
 --分入转分出的业务，分出的账单找对应的分入账单的保费
select max(cat_parent.acc_writeoffsum) writeoffamout, fin.policysn
  from ciod_ri.account_catalog       cat_self,
       ciod_ri.account_catalog       cat_parent,
       ciod_ri.ri_fac_cont_reins_fin fin
 where cat_self.premium_bill_no = cat_parent.bill_no
   and cat_parent.bill_no = fin.statement_no
   and cat_self.retrocession_flag = 'T'
   and cat_parent.acc_writeoffsum <> 0
 group by fin.policysn
) t
;

SQL执行计划为

Plan hash value: 3741877562
------------------------------------------------------------------------------------------------------------------------
| Id  | Operation                          | Name                      | Rows  | Bytes |TempSpc| Cost (%CPU)| Time     |
------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                   |                           |   458K|    64M|       | 27972   (2)| 00:05:36 |
|*  1 |  VIEW                              | T_POLICY_PAYMENT_WRITEOFF |   458K|    64M|       | 27972   (2)| 00:05:36 |
|   2 |   COUNT                            |                           |       |       |       |            |          |
|   3 |    VIEW                            |                           |   458K|    59M|       | 27972   (2)| 00:05:36 |
|   4 |     UNION-ALL                      |                           |       |       |       |            |          |
|   5 |      HASH GROUP BY                 |                           |   458K|    24M|    59M| 23812   (2)| 00:04:46 |
|*  6 |       HASH JOIN                    |                           |   458K|    24M|    12M| 17447   (2)| 00:03:30 |
|*  7 |        TABLE ACCESS FULL           | MM_WRITEOUTSTATUS_TO      |   458K|  7159K|       |  2938   (2)| 00:00:36 |
|   8 |        TABLE ACCESS FULL           | MM_WRITEOUT_TO            |  1241K|    48M|       | 10757   (2)| 00:02:10 |
|   9 |      HASH GROUP BY                 |                           |   795 | 81090 |       |  4161   (1)| 00:00:50 |
|* 10 |       HASH JOIN                    |                           |   795 | 81090 |       |  4160   (1)| 00:00:50 |
|  11 |        NESTED LOOPS                |                           |   795 | 38955 |       |  3683   (1)| 00:00:45 |
|* 12 |         TABLE ACCESS FULL          | ACCOUNT_CATALOG           |   724 |  2896 |       |  2234   (2)| 00:00:27 |
|* 13 |         TABLE ACCESS BY INDEX ROWID| ACCOUNT_CATALOG           |     1 |    45 |       |     2   (0)| 00:00:01 |
|* 14 |          INDEX UNIQUE SCAN         | PK_ACCOUNT_CATALOG        |     1 |       |       |     1   (0)| 00:00:01 |
|  15 |        TABLE ACCESS FULL           | RI_FAC_CONT_REINS_FIN     | 93390 |  4833K|       |   475   (2)| 00:00:06 |
------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - filter("POLICYSN"='PB12345')
   6 - access("A"."ID"="B"."ID")
   7 - filter("A"."WRITEOUTTYPE"='1' AND "A"."DATASOURCE"='RI' AND "A"."STATUS"='99')
  10 - access("CAT_PARENT"."BILL_NO"="FIN"."STATEMENT_NO")
  12 - filter("CAT_SELF"."PREMIUM_BILL_NO" IS NOT NULL AND "CAT_SELF"."RETROCESSION_FLAG"='T')
  13 - filter("CAT_PARENT"."ACC_WRITEOFFSUM"<>0)
  14 - access("CAT_SELF"."PREMIUM_BILL_NO"="CAT_PARENT"."BILL_NO")

分析

根据执行计划中，ID=7与ID=15,MM_WRITEOUTSTATUS_TO与RI_FAC_CONT_REINS_FIN 是全表扫描方式去访问表。
谓词条件是 where policysn = 'PB12345';
然后我们可以在MM_WRITEOUTSTATUS_TO表的字段CUSTSEQ建立索引
RI_FAC_CONT_REINS_FIN表的字段POLICYSN建立索引，使其能进行谓词推入，并进行索引访问。
但是视图t_policy_payment_writeoff 有rownum 字段，会阻止进行谓词推入，所以我们可以改写该视图。

优化

1）增加索引

create index CIOD_BP.IDX_CUSTSEQ_1 on CIOD_BP.MM_WRITEOUT_TO (CUSTSEQ);
create index ciod_ri.IDX_POLICYSN_1 on ciod_ri.RI_FAC_CONT_REINS_FIN (POLICYSN);

2）改写视图,去掉rownum as id 字段

create or replace view t_policy_payment_writeoff as
select  t."WRITEOFFAMOUT",t."POLICYSN"
 from (
select sum(b.realamount) writeoffamout, b.custseq policysn
        --保费回写视图
          from ciod_bp.mm_writeoutstatus_to a, ciod_bp.mm_writeout_to b
         where a.id = b.id
           and a.datasource = 'RI'
           and a.status = '99'
           and a.writeouttype = '1' --回写成功的..
         group by b.custseq
 union all
 --分入转分出的业务，分出的账单找对应的分入账单的保费
select max(cat_parent.acc_writeoffsum) writeoffamout, fin.policysn
  from ciod_ri.account_catalog       cat_self,
       ciod_ri.account_catalog       cat_parent,
       ciod_ri.ri_fac_cont_reins_fin fin
 where cat_self.premium_bill_no = cat_parent.bill_no
   and cat_parent.bill_no = fin.statement_no
   and cat_self.retrocession_flag = 'T'
   and cat_parent.acc_writeoffsum <> 0
 group by fin.policysn
) t

3）原sql改成

select rownum as id,b.* from t_policy_payment_writeoff b where policysn = 'PB12345';
#执行计划
----------------------------------------------------------------------------------------------------------
| Id  | Operation                        | Name                  | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                 |                       |     2 |   270 |  2252   (2)| 00:00:28 |
|   1 |  VIEW                            |                       |     2 |   270 |  2252   (2)| 00:00:28 |
|   2 |   UNION-ALL                      |                       |       |       |            |          |
|   3 |    SORT GROUP BY NOSORT          |                       |     1 |    57 |    11   (0)| 00:00:01 |
|*  4 |     TABLE ACCESS BY INDEX ROWID  | MM_WRITEOUTSTATUS_TO  |     1 |    16 |     3   (0)| 00:00:01 |
|   5 |      NESTED LOOPS                |                       |     2 |   114 |    11   (0)| 00:00:01 |
|   6 |       TABLE ACCESS BY INDEX ROWID| MM_WRITEOUT_TO        |     2 |    82 |     5   (0)| 00:00:01 |
|*  7 |        INDEX RANGE SCAN          | IDX_CUSTSEQ_1         |     2 |       |     3   (0)| 00:00:01 |
|*  8 |       INDEX RANGE SCAN           | IDX_WRITEOUTSTATUS_1  |     1 |       |     2   (0)| 00:00:01 |
|   9 |    SORT GROUP BY NOSORT          |                       |     1 |   102 |  2241   (2)| 00:00:27 |
|* 10 |     HASH JOIN                    |                       |     1 |   102 |  2241   (2)| 00:00:27 |
|  11 |      NESTED LOOPS                |                       |     2 |   196 |     7   (0)| 00:00:01 |
|  12 |       TABLE ACCESS BY INDEX ROWID| RI_FAC_CONT_REINS_FIN |     2 |   106 |     3   (0)| 00:00:01 |
|* 13 |        INDEX RANGE SCAN          | IDX_POLICYSN_1        |     2 |       |     1   (0)| 00:00:01 |
|* 14 |       TABLE ACCESS BY INDEX ROWID| ACCOUNT_CATALOG       |     1 |    45 |     2   (0)| 00:00:01 |
|* 15 |        INDEX UNIQUE SCAN         | PK_ACCOUNT_CATALOG    |     1 |       |     1   (0)| 00:00:01 |
|* 16 |      TABLE ACCESS FULL           | ACCOUNT_CATALOG       |   724 |  2896 |  2234   (2)| 00:00:27 |
----------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
   4 - filter("A"."WRITEOUTTYPE"='1' AND "A"."DATASOURCE"='RI' AND "A"."STATUS"='99')
   7 - access("B"."CUSTSEQ"='PB12345')
   8 - access("A"."ID"="B"."ID")
  10 - access("CAT_SELF"."PREMIUM_BILL_NO"="CAT_PARENT"."BILL_NO")
  13 - access("FIN"."POLICYSN"='PB12345')
  14 - filter("CAT_PARENT"."ACC_WRITEOFFSUM"<>0)
  15 - access("CAT_PARENT"."BILL_NO"="FIN"."STATEMENT_NO")
  16 - filter("CAT_SELF"."PREMIUM_BILL_NO" IS NOT NULL AND "CAT_SELF"."RETROCESSION_FLAG"='T')

优化后

SQL运行时间降至：0.034s