Re: Histogram Q

*grin* Kinda. As far as I know, we do not gather any explicit stats on the system objects. But I have 40 objects from this query:

  1 select TABLE_NAME,COLUMN_NAME,NUM_DISTINCT,NUM_NULLS,SAMPLE_SIZE   2 from dba_tab_cols where NUM_BUCKETS = 1 and HISTOGRAM = 'HEIGHT BALANCED'
  3* and owner in ('SYS','SYSTEM')

According to dba_histograms, they all have 1 row (as you mentioned). Not a big deal, just another quirkiness. A good thing the density is not "height balanced". =)

On 12/13/06, Wolfgang Breitling <breitliw_at_centrexcc.com> wrote:
>
> Charles,
>
> I suspect you are referring to the case when you (or size skewonly)
> collect a histogram requesting more than 1 bucket for a column with
> num_distinct=1 (all rows have the same value for that column). You'll get a
> histogram with one single row in dba_histograms - a 'size 1' "histogram" has
> two rows in dba_histogram - which is really a frequency histogram (as it
> should be when size > num_distinct) but is labelled a HB histogram in
> dba_tab_columns.histogram.
>
> At 10:29 AM 12/13/2006, Charles Schultz wrote:
>
> Be careful with that. It is possible to have a height-balanced histogram
> with one bucket, according some of those views. Granted, it is not really a
> histogram at all, but the views have some funky logic in them.
>
> On 12/13/06, *Allen, Brandon* < Brandon.Allen_at_oneneck.com> wrote:
> You are correct - 1 bucket = "no histogram". You can also query for
> user_tab_columns.histogram = 'NONE' to confirm.
>
> Regards
>
> Wolfgang Breitling
> Centrex Consulting Corporation
> www.centrexcc.com
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-- 
Charles Schultz

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