Posted by lsllcm on 11/26/07 14:56

Hi All,

I have one question about many "or" operation make system choose
incorrect index

There is one table TT (
C1 VARCHAR(15) NOT NULL,
C2 VARCHAR(15) NOT NULL,
C3 VARCHAR(15) NOT NULL,
C4 VARCHAR(15) NOT NULL
C5 VARCHAR2(200),
)

Primary Key TT_PK (C1, C2, C3, C4)

SELECT C1, C2, C3, C4 FROM TT WHERE C1 = 'TEST' AND ((C2 =
'07RES' AND C3 = '00000' AND C4 = '02383') OR (C2 = '07RES' AND
C3 = '00000' AND C4 = '02382') OR (C2 = '07RES' AND C3 = '00000'
AND C4 = '02381') OR (C2 = '07RES' AND C3 = '00000' AND C4 =
'02380') OR (C2 = '07RES' AND C3 = '00000' AND C4 = '02379') OR
(C2 = '07RES' AND C3 = '00000' AND C4 = '02378') OR (C2 = '07RES'
AND C3 = '00000' AND C4 = '02377') OR (C2 = '07RES' AND C3 =
'00000' AND C4 = '02376') OR (C2 = '07RES' AND C3 = '00000' AND
C4 = '02375') OR (C2 = '07RES' AND C3 = '00000' AND C4 =
'02374') OR (C2 = '07RES' AND C3 = '00000' AND C4 = '02373') OR
(C2 = '07RES' AND C3 = '00000' AND C4 = '02372')
.... about 100 or operations
OR (C2 = '07COM' AND C3 = '00000' AND C4 = '00618') OR (C2 =
'07COM' AND C3 = '00000' AND C4 = '00617') OR (C2 = '07COM' AND
C3 = '00000' AND C4 = '00616') OR (C2 = '07COM' AND C3 = '00000'
AND C4 = '00608') )

The system choose index prefix, and query all index leaf with
C1='TEST'

Prefix: [dbo].[TT].C1 = 'TEST'

After I reduce the OR operators to 50, it use choose

Prefix: [dbo].[TT].C1, [dbo].[TT].C2,[dbo].[TT].C3,[dbo].[TT].C4=
'TEST, '07RES', '00000', '02383'
Then Merge Join, it is very quick,

Can anyone help on this, do I have to reduce the OR operator to 50?

Thanks in advance!

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