RE: Histograms - SIZE clause & num_buckets anomaly (with a piggyback question)
- From: Wolfgang Breitling <breitliw@xxxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Tue, 03 Aug 2004 10:17:23 -0600
You have a compressed HB histogram - one with popular values - if
dba_tab_columns.num_buckets < max(dba_histograms.endpoint_number).
There is a slim theoretical chance that that condition is true for a
frequency histogram, however, in general
num_buckets = 1 ( = max(endpoint_number) ==> no histogram
num_buckets = num_distinct-1 ==> frequency histogram
num_buckets = max(endpoint_number) ==> HB histogram without popular values
( this includes case one, treating the entire value range as one big bucket)
num_buckets < max(endpoint_number) ==> HB histogram with popular values
At 06:33 AM 8/3/2004, you wrote:
>How to identify if the actual number of buckets is different from the value
>shown in NUM_BUCKETS column of USER_TAB_COLUMNS?
>
>Thanks & regards,
>Charu.
Regards
Wolfgang Breitling
Centrex Consulting Corporation
www.centrexcc.com
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