需要优化的SQL
SELECT *
FROM (SELECT A.*, ROWNUM R
FROM (SELECT DISTINCT A.NDOCID AS NDOCID,
TO_CHAR(NVL(A.DMODIFYDATE, A.DCREATEDATE),
'yyyy-MM-dd hh24:mi:ss') AS DMODIFYDATE,
NVL(A.CURTITLE, ' ') AS CTITLE,
A.DMODIFYDATE AS DM,
A.DCREATEDATE,
A.CURTITLE,
A.NPROCID,
A.NPROCSTATUS,
A.NDOCSORTID,
A.NMANAGERID,
GW.CDOCPRIORITY,
GW.CFWDW,
GW.WENHAO,
GW.CDOCUTYPE,
COUNT(A.NDOCID) OVER() AS ROWNUMBER
FROM WF_DOC_GW A,
(SELECT NDOCID,
NJJCD,
CBT AS CTITLE,
CFWDW,
NVL(CDOCFROM, '本单位发文') AS CDOCFROM,
NVL(CDOCPRIORITY, 100) AS CDOCPRIORITY,
NVL(CFWZH, '无文号') AS WENHAO,
CDOCUTYPE,
CFWYDW
FROM WF_DOC_GW_SHOUWEN SW
UNION ALL
SELECT NDOCID,
NJJCD,
CBT AS CTITLE,
CFWDW,
NVL(CDOCFROM, '本单位发文') AS CDOCFROM,
NVL(CDOCPRIORITY, 0) AS CDOCPRIORITY,
NVL(CWENHAO, '无文号') AS WENHAO,
CDOCUTYPE,
CFWYDW
FROM WF_DOC_GW_FAWEN FW) GW
WHERE ((A.NPROCID = 20 AND A.NPROCSTATUS = 1) OR
(A.NPROCID <> 20))
AND (A.NSTATE = 0 OR (A.NSTATE = 2 AND A.NDOCSORTID = 1))
AND A.NDOCSORTID IN (1, 2)
AND ((INSTR(',' || A.CPROCUSERLIST || ',',
',' || '4301' || ',') > 0 AND
A.NDOCID NOT IN
(SELECT GI.SRC_NDOCID
FROM WF_DOC_GW_INNER GI
WHERE GI.SRC_USERID = 4301
AND GI.RETURNSTATUS IS NULL
AND GI.SRC_NDOCID IS NOT NULL)) OR
A.NPROCUID = 4301)
AND (A.NMSGID = 0 OR
(A.NMSGID IS NOT NULL AND A.NFWQBOPT = 10))
AND GW.NDOCID = A.NDOCID
ORDER BY A.DMODIFYDATE DESC, GW.CDOCPRIORITY DESC) A
WHERE ROWNUM <= 13) B
WHERE R > 0
执行计划
------------------------------------------------------------------------- | Id | Operation | Name | E-Rows | ------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | |* 1 | VIEW | | 13 | |* 2 | COUNT STOPKEY | | | | 3 | VIEW | | 261 | |* 4 | SORT UNIQUE STOPKEY | | 261 | | 5 | WINDOW BUFFER | | 261 | |* 6 | FILTER | | | |* 7 | HASH JOIN | | 90557 | |* 8 | TABLE ACCESS FULL | WF_DOC_GW | 84010 | | 9 | VIEW | | 261K| | 10 | UNION-ALL | | | | 11 | TABLE ACCESS FULL | WF_DOC_GW_SHOUWEN | 242K| | 12 | TABLE ACCESS FULL | WF_DOC_GW_FAWEN | 18876 | |* 13 | TABLE ACCESS BY INDEX ROWID| WF_DOC_GW_INNER | 1 | |* 14 | INDEX RANGE SCAN | IDX_INNER_SRCDOCID | 2 | -------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("R">0)
2 - filter(ROWNUM<=13)
4 - filter(ROWNUM<=13)
6 - filter(((INSTR(','||"A"."CPROCUSERLIST"||',',',4301,')>0 AND IS NULL) OR "A"."NPROCUID"=4301))
8 - filter((("A"."NSTATE"=0 OR ("A"."NSTATE"=2 AND "A"."NDOCSORTID"=1)) AND ("A"."NPROCID"<>20 OR
("A"."NPROCSTATUS"=1 AND "A"."NPROCID"=20)) AND ("A"."NMSGID"=0 OR ("A"."NFWQBOPT"=10 AND "A"."NMSGID" IS NOT
NULL)) AND INTERNAL_FUNCTION("A"."NDOCSORTID")))
12 - access("NDOCID"="A"."NDOCID")
14 - access("NDOCID"="A"."NDOCID")
15 - filter(("GI"."SRC_USERID"=4301 AND "GI"."RETURNSTATUS" IS NULL))
16 - access("GI"."SRC_NDOCID"=:B1)
filter("GI"."SRC_NDOCID" IS NOT NULL)
该条SQL执行后的结果集只有2条数据，WF_DOC_GW_SHOUWEN数据量有24万，NDOCID是主键，从执行计划看，走的是全表扫描，和预期结果不符合，应该走的是唯一索引才对，优化的思路是先关联WF_DOC_GW和WF_DOC_GW_INNER，计算出结果集后，再关联WF_DOC_GW_SHOUWEN，这样就会走唯一索引，使用push_subq可以达到想要到想过，修改后的SQL如下
SELECT *
FROM (SELECT A.*, ROWNUM R
FROM (SELECT /*+ push_subq(@tmp)*/
DISTINCT A.NDOCID AS NDOCID,
TO_CHAR(NVL(A.DMODIFYDATE, A.DCREATEDATE),
'yyyy-MM-dd hh24:mi:ss') AS DMODIFYDATE,
NVL(A.CURTITLE, ' ') AS CTITLE,
A.DMODIFYDATE AS DM,
A.DCREATEDATE,
A.CURTITLE,
A.NPROCID,
A.NPROCSTATUS,
A.NDOCSORTID,
A.NMANAGERID,
GW.CDOCPRIORITY,
GW.CFWDW,
GW.WENHAO,
GW.CDOCUTYPE,
COUNT(A.NDOCID) OVER() AS ROWNUMBER
FROM WF_DOC_GW A,
(SELECT NDOCID,
NJJCD,
CBT AS CTITLE,
CFWDW,
NVL(CDOCFROM, '本单位发文') AS CDOCFROM,
NVL(CDOCPRIORITY, 100) AS CDOCPRIORITY,
NVL(CFWZH, '无文号') AS WENHAO,
CDOCUTYPE,
CFWYDW
FROM WF_DOC_GW_SHOUWEN SW
UNION ALL
SELECT NDOCID,
NJJCD,
CBT AS CTITLE,
CFWDW,
NVL(CDOCFROM, '本单位发文') AS CDOCFROM,
NVL(CDOCPRIORITY, 0) AS CDOCPRIORITY,
NVL(CWENHAO, '无文号') AS WENHAO,
CDOCUTYPE,
CFWYDW
FROM WF_DOC_GW_FAWEN FW) GW
WHERE ((A.NPROCID = 20 AND A.NPROCSTATUS = 1) OR
(A.NPROCID <> 20))
AND (A.NSTATE = 0 OR (A.NSTATE = 2 AND A.NDOCSORTID = 1))
AND A.NDOCSORTID IN (1, 2)
AND ((INSTR(',' || A.CPROCUSERLIST || ',',
',' || '4301' || ',') > 0 AND
A.NDOCID NOT IN
(SELECT /*+ qb_name(tmp)*/
GI.SRC_NDOCID
FROM WF_DOC_GW_INNER GI
WHERE GI.SRC_USERID = 4301
AND GI.RETURNSTATUS IS NULL
AND GI.SRC_NDOCID IS NOT NULL)) OR
A.NPROCUID = 4301)
AND (A.NMSGID = 0 OR
(A.NMSGID IS NOT NULL AND A.NFWQBOPT = 10))
AND GW.NDOCID = A.NDOCID
ORDER BY A.DMODIFYDATE DESC, GW.CDOCPRIORITY DESC) A
WHERE ROWNUM <= 13) B
WHERE R > 0
------------------------------------------------------------------------------------------------------------ | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------------------------------------ | 0 | SELECT STATEMENT | | 13 | 9984 | 2518 (1)| 00:00:31 | |* 1 | VIEW | | 13 | 9984 | 2518 (1)| 00:00:31 | |* 2 | COUNT STOPKEY | | | | | | | 3 | VIEW | | 244 | 179K| 2518 (1)| 00:00:31 | |* 4 | SORT UNIQUE STOPKEY | | 244 | 63928 | 2517 (1)| 00:00:31 | | 5 | WINDOW BUFFER | | 244 | 63928 | 2518 (1)| 00:00:31 | | 6 | NESTED LOOPS | | 244 | 63928 | 2516 (1)| 00:00:31 | |* 7 | TABLE ACCESS FULL | WF_DOC_GW | 242 | 27588 | 1547 (2)| 00:00:19 | |* 8 | TABLE ACCESS BY INDEX ROWID | WF_DOC_GW_INNER | 1 | 17 | 2 (0)| 00:00:01 | |* 9 | INDEX RANGE SCAN | IDX_INNER_SRCDOCID | 2 | | 1 (0)| 00:00:01 | | 10 | VIEW | | 1 | 148 | 4 (0)| 00:00:01 | | 11 | UNION ALL PUSHED PREDICATE | | | | | | | 12 | TABLE ACCESS BY INDEX ROWID| WF_DOC_GW_SHOUWEN | 1 | 49 | 2 (0)| 00:00:01 | |* 13 | INDEX UNIQUE SCAN | PK_WF_DOC_GW_SHOUWEN | 1 | | 1 (0)| 00:00:01 | | 14 | TABLE ACCESS BY INDEX ROWID| WF_DOC_GW_FAWEN | 1 | 38 | 2 (0)| 00:00:01 | |* 15 | INDEX UNIQUE SCAN | PK_WF_DOC_GW_FAWEN | 1 | | 1 (0)| 00:00:01 |
优化前的逻辑读是12000，优化后的逻辑读降到了5000，还是蛮有效果的