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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Composite indices and skip scanning
As always the choice between using a skip scan or FTS is a CBO decision and
will largely depend on the nature of the object statistics and the SQL.
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Boyle, Christopher J.
Sent: Thursday, April 15, 2004 9:11 AM
To: oracle-l_at_freelists.org
Subject: Composite indices and skip scanning
Oracle 9.2.0.2.0=20
I have an intersection table composed of PK_TABLE_A, PK_TABLE_B which is being used to handle a M:M relationship between A and B. There is a unique constraint on the combination of the two entries and a corresponding index with A as the leading value. When I was trying to access table A using the PK from table B I expected it to use that index because of the 9i skip scan feature that allows for a non leading index member to still utilize the index. What I got was a FTS until I added a separate index on PK_TABLE_B only. Is there something with a unique index that prevents skip scanning? Or do I have too much blood in my caffeine and am mis-rembering how the indices should work?
Thanks,
Chris =20
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