Cherie,
Very interesting...
Is there a recommendation for determining the correct
number of buckets for each histogram? (I'm cut off
from metalink at the moment)
Thanks,
Scott Shafer
San Antonio, TX
- Cherie_Machler_at_gelco.com wrote:
> Listers,
>
> Here's an interesting fact about histograms that I
> was unaware of (and I bet
> most
> of you are unaware of too).
>
> When a table is just plain analyzed, histograms are
> automatically created
> with a bucket size of 1 for each column in each
> table. You can see these
> buckets/histograms by querying the dba_tab_columns
> table and the
> dba_tab_histograms(Oracle 8+) or the dba_histograms
> (pre-Oracle8) table .
>
> Apparently a single-bucket histogram is the same as
> having no histogram.
> There is basically no effect on the explain plan
> when you have a single-bucket
> histogram because all of the possible values for the
> histogram are in the
> same bucket.
>
> I discovered this from an obscure newsgroup post
> while searching Metalink.
>
> Cherie
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Received on Wed Aug 16 2000 - 12:58:56 CDT
