SOLVED: histogram oddity: Height-balanced histograms where NDV < num_buckets
- From: "Charles Schultz" <sacrophyte@xxxxxxxxx>
- To: oracle-l <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 4 Oct 2006 12:27:01 -0500
Oracle Support has finally acknowledged that this is an unpublished internal
bug fixed in v11. As no other customers have reported the issue, much less a
performance issue, there are no plans for a backport.
The good news is that even though the buckets are mismarked (HEIGHT
BALANCED), the density of the column matches that of a FREQUENCY histogram.
At least for our situation it does.
On 8/11/06, Charles Schultz <sacrophyte@xxxxxxxxx> wrote:
Oracle 10.2.0.2, Solaris 8
Wondering if anyone could explain this. We have 105 SYS-owned tables where
num_distinct < num_buckets according to dba_tab_col_statistics (see
following query). Even weirder, some columns have 217 buckets for only 1
distinct value (verified in dba_tab_histograms). What kind of sense does
that make? Similarly, we have one application partition that exhibits the
same symptom.
select distinct table_name, column_name, num_distinct, num_buckets
from dba_tab_col_statistics where histogram = 'HEIGHT BALANCED' and
num_distinct < num_buckets
order by num_distinct,num_buckets
/
-mystified
--
Charles Schultz
--
Charles Schultz
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