| Index with NVL [message #483222] |
Fri, 19 November 2010 05:07  |
ss1_3
Messages: 4
Registered: December 2009
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Junior Member |
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I have a query which had a join:
a.c1=b.c1 and a.c2=@var
where @var is user supplied input at runtime
We had a index on a.c2 . The CBO would use this index to generate an opitimised query plan.
We found some records from table "b" were dropping due to inner join. So we made a change in join. It'd be like
a.c1(+)=b.c1 and nvl(a.c2,@var)=@var
This query is no longer using the index, instead its doing a full table scan causing the query to slowdown.
I have tried creating index on
nvl(a.c2,'31-dec-9999')
But the CBO won't use it.Anyway to create index on this col so that full table scan can be avoided?
Thanks
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| Re: Index with NVL [message #483244 is a reply to message #483241] |
Fri, 19 November 2010 08:00  |
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Michel Cadot
Messages: 68647
Registered: March 2007
Location: Nanterre, France, http://...
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Senior Member
Account Moderator |
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Quote:I have tried creating index on
nvl(a.c2,'31-dec-9999')
But the CBO won't use it.
First, because '31-dec-9999' is not a date but a string.
Quote:Anyway to create index on this col so that full table scan can be avoided?
Why do you think FTS is bad?
Regards
Michel
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