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Don Burleson Blog 









Oracle statistics bugs cause poor SQL execution plans

Oracle Database Tips by Donald Burleson

MOSC note 337096.1 notes that there are bugs in the dbms_stats collection process and that these can lead to sub-optimal SQL execution plans.  To counter the bugs Oracle has introduced a new validate_stats procedure.

The validate_stats procedure

Oracle notes "The VALIDATE_STATS package helps Oracle Support and its customers to detect bugs and limitations of the statistics gathered by the DBMS_STATS package that could cause sub-optimal execution plans."  The MOSC notes provides download and execution instructions.

Related statistics bugs includes:

  • Bug 3620168 - Dbms_Stats: Method_Opt='For All Indexed Columns' Always Sets Avg_Row_Len = 100
  • Bug 4055596 - Dbms_Stats With Cascade True Not Generating Stats For Mv Index
  • Bug 4495422 - Wrong Ndv For Char Column W/Unique Values Where The First 32 Char Arent Unique

If you like Oracle tuning, you may enjoy my new book "Oracle Tuning: The Definitive Reference", over 900 pages of my favorite tuning tips & scripts. 

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.



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