Re: Function Based Index
- From: Stefano Cislaghi <s.cislaghi@xxxxxxxxx>
- To: Brandon.Allen@xxxxxxxxxxx
- Date: Mon, 10 Sep 2012 17:58:29 +0200
I agree. Anyway if you do not provide us more information and the
query anything we might say are only theory and guessworks.
Ste
On 10 September 2012 17:48, Allen, Brandon <Brandon.Allen@xxxxxxxxxxx> wrote:
> Maybe the CBO is choosing not to use the index because the percentage of
> blocks it thinks you will need is too high? I don't know exactly how the CBO
> calculates it, but the general rule of thumb is to only use an index if
> you're going to read less than 5% of the table's blocks. If the values in
> your look up column are skewed, you could try running the query with an
> unpopular value such that Oracle will be more likely to use an index (make
> sure you flush the old plans out of the pool first), and then, if it does
> load the plan with the index, you can create a sql plan baseline to make it
> stick with that plan for future executions - that is assuming you're on 11g;
> create a stored outline if you're on 10g.
>
> Regards,
> Brandon
>
>
>
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