RE: Histograms - SIZE clause & num_buckets anomaly (with a piggyback question)

From: Wolfgang Breitling <breitliw_at_centrexcc.com>
Date: Tue, 03 Aug 2004 10:17:23 -0600
Message-Id: <6.1.0.6.2.20040803094827.02fcdd68@pop.centrexcc.com>

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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Received on Tue Aug 03 2004 - 11:13:32 CDT