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Home -> Community -> Usenet -> c.d.o.server -> Re: Creating and validating a histogram
tdry_at_yet2.com wrote:
>
> I have a column that is holding true/false type values and 99% of the
> values are true and yet we are regularly looking for those which are
> false. Of course, the answer is to create a histogram which will let
> the cost based optimizer intelligently do the correct thing. My problem
> is that the execution plan is not changing after I analyze the column.
> I'm also not sure how to interpret the contents of user_histograms and
> user_tab_columns to validate that the histogram really exists.
>
> Here are the two different commands that I've used to generate the
> histograms:
>
> analyze index tablea_idx compute statistics
> for columns true_false size 2;
>
> analyze table tablea compute statistics
> for columns true_false size 2;
>
> Both statements generate the same data in user_tab_columns with a
> "num_buckets" value of 1. Below are the values in user_histograms after
> running the two analyze commands respectively:
>
> table column endpoint number
> TABLEA TRUE_FALSE 0
> TABLEA TRUE_FALSE 1
>
> TABLEA TRUE_FALSE 15
> TABLEA TRUE_FALSE 1371
>
> The database version is 7.3.4. Any thoughts?
>
> -Tim
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
Some other options:
both you give you very small and very fast indexes..
HTH
--
"Some days you're the pigeon, and some days you're the statue." Received on Wed Jan 05 2000 - 07:16:11 CST
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