RE: How does DBMS_STATS select columns to generate histograms?

Hi Mladen

>Does anybody know the where clause used to select columns which=20
>will have histograms? Is there a fixed cutoff number =
(EQUALITY_PREDS>x)?
>Percentage?

Honestly I don't know exactly... In any case I have a demo, which I show = when I'm trying to explain how 'SIZE AUTO' works, where a single = statement (i.e. predicate) is enough to lead to the histogram gathering. = I also observed that the timestamp is important, i.e. old entries are = not considered (sorry, I never did extensive tests to find out after how = many days they are no more considered...).=20

Also note that the CBO only increases the counters when a statement is = parsed, i.e. the absolute value is therefore so not important....

Therefore, IMHO, they simply give a look if in the last x days the = column has been used in a predicate.=20

Corrections and addition information is highly welcome!

HTH
Chris

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