以下语句完全正确,但COST较高,原因是因为AEH、AEC、AC、ACSN几张表都有数百万条记录,
由于采用了HASH连接,尝试采用优化索引等多种方式,但是由于记录过多,表的查询条件相对较少,
COST下降幅度始终很有限,COST提高到1000出头已经很尽力了。
Select Count(Tmp.Id)
From (Select Rownum As Id, t.Entry_Id, t.Container_Id, Con.Container_Num
From AEC t
Inner Join AEH Head On t.Entry_Id = Head.Entry_Id
Inner Join AC Con On t.Container_Id = Con.Id And Head.Deleted_Flag = '0' And Con.Deleted_Flag = '0') Tmp
Inner Join ACSN Constatus On Tmp.Container_Id = Constatus.Container_Id And
Constatus.Px_Operation_Status <> '0'
And Tmp.Entry_Id = :B2
And Tmp.Container_Num = :B1
SELECT STATEMENT, GOAL = ALL_ROWS Cost=3519 Cardinality=1 Bytes=62
SORT AGGREGATE Cardinality=1 Bytes=62
MERGE JOIN Cost=3519 Cardinality=51 Bytes=3162
TABLE ACCESS BY INDEX ROWID Object owner=TEST Object name=ACSN Cost=774 Cardinality=49 Bytes=343
INDEX FULL SCAN Object owner=TEST Object name=FK_A_C_C_S_P Cost=6 Cardinality=1849
SORT JOIN Cost=2745 Cardinality=1470 Bytes=80850
VIEW Object owner=TEST Cost=2744 Cardinality=1470 Bytes=80850
COUNT
HASH JOIN Cost=2744 Cardinality=1470 Bytes=94080
NESTED LOOPS Cost=1494 Cardinality=1470 Bytes=64680
INDEX FAST FULL SCAN Object owner=TEST Object name=IDX_A_E_C Cost=5 Cardinality=1470 Bytes=33810
TABLE ACCESS BY INDEX ROWID Object owner=TEST Object name=AEH Cost=2 Cardinality=1 Bytes=21
INDEX UNIQUE SCAN Object owner=TEST Object name=PK_AEH Cost=1 Cardinality=1
TABLE ACCESS FULL Object owner=TEST Object name=A_CO Cost=1220 Cardinality=1005299 Bytes=20105980
但再细看可以发现有如下苗头:
And Tmp.Entry_Id = :B2
And Tmp.Container_Num = :B1
两个条件是等AEC、AEH、AC三个表HASH连接后才做的过滤,为啥不在连接前就对表做过滤,
再一查在AEH表中有Entry_Id字段,而Container_Num是AC中的一个字段,于是把这两个
条件从对TMP的外层过滤移入到AEH、AC内层过滤中,语句如下;
Select Count(Tmp.Id)
From (Select Rownum As Id, t.Entry_Id, t.Container_Id, Con.Container_Num
From AEC t
Inner Join AEH Head On t.Entry_Id = Head.Entry_Id And Head.Entry_Id = :B2 --迁移条件Head.Entry_Id = :B2到此处
Inner Join AC Con On t.Container_Id = Con.Id And Head.Deleted_Flag = '0' And Con.Deleted_Flag = '0'
And con.Container_Num = :B1) Tmp --迁移条件con.Container_Num = :B1到此处
Inner Join ACSN Constatus On Tmp.Container_Id = Constatus.Container_Id And
Constatus.Px_Operation_Status <> '0'
--And Tmp.Entry_Id = :B2
--And Tmp.Container_Num = :B1
实测结果表明,COST已经下降到了9,提升近500倍,相信这个效果是大家乐意接受的。
SELECT STATEMENT, GOAL = ALL_ROWS Cost=9 Cardinality=1 Bytes=33
SORT AGGREGATE Cardinality=1 Bytes=33
NESTED LOOPS Cost=9 Cardinality=1 Bytes=33
VIEW Object owner=TEST Cost=7 Cardinality=1 Bytes=26
COUNT
NESTED LOOPS Cost=7 Cardinality=1 Bytes=64
NESTED LOOPS Cost=5 Cardinality=1 Bytes=44
TABLE ACCESS BY INDEX ROWID Object owner=TEST Object name=AEH Cost=3 Cardinality=1 Bytes=21
INDEX UNIQUE SCAN Object owner=TEST Object name=PK_AEH Cost=2 Cardinality=1
INDEX RANGE SCAN Object owner=TEST Object name=IDX_A_E_C Cost=2 Cardinality=1 Bytes=23
TABLE ACCESS BY INDEX ROWID Object owner=TEST Object name=AC Cost=2 Cardinality=1 Bytes=20
INDEX UNIQUE SCAN Object owner=TEST Object name=IDX_C Cost=1 Cardinality=1
TABLE ACCESS BY INDEX ROWID Object owner=TEST Object name=ACSN Cost=2 Cardinality=1 Bytes=7
INDEX UNIQUE SCAN Object owner=TEST Object name=FK_A_C_C_S_P Cost=1 Cardinality=1
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