Easy test case:
CREATE TABLE TEST_SKIP
(
C1 NUMBER NOT NULL,
C2 NUMBER NOT NULL,
C3 NUMBER NULL
);
CREATE UNIQUE INDEX TESTSKIP1
ON TEST_SKIP(C1,C2);
select --+ index_ss(test_skip, )
c1,c2,c3
from test_skip
where c2 = 10;
OPERATION OPTIONS OBJECT_NAME
SELECT STATEMENT [NULL] [NULL]
TABLE ACCESS BY INDEX ROWID TEST_SKIP
INDEX SKIP SCAN TESTSKIP1
Regards,
Waleed
-----Original Message-----
Sent: Wednesday, May 28, 2003 7:00 AM
To: Multiple recipients of list ORACLE-L
Okay, I have a developer here who has been reading the docs (this can
be dangerous!)
we are adding functionality to one of our applications, this will
involve using multiple fulfillment houses, so we'll be adding the
fulfillment vendor id to the order table. Easy, this is not a problem.
We want to be able to search by order date and by fulfillment vendor
id/order date
Traditional design would be to add two indexes: one on order date, and
a concatenated one on fulfillment vendor id/order date.
The developer is telling me to create a "skip scan index" instead of
two different ones. MY reading in the FM tells me that skip scan index
is not a type of index, but rather a way Oracle uses to use an index
even if the leftmost column is not in the query.
Is there any benefit in my building only the one index? Our order
volume is not so high (and never will be) that there is a visible
performance impact if I have the two indices.
This is 9i, 9.2.0.1, will be upgrading to 9.2.0.2 in the near future.
Solaris
Any suggestions/comments/war stories would be appreciated. I know I've
seen Jonathan post on skip scan indexes before but I can't find the
specific reference at the moment.
Rachel
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