Unexpected Poor Execution Plan When Non-Popular Value Missing from Histogram
(Doc ID 1563752.1)
Last updated on FEBRUARY 03, 2019
Applies to:Oracle Database - Enterprise Edition - Version 18.104.22.168 to 22.214.171.124 [Release 11.2]
Information in this document applies to any platform.
A poor plan is chosen for predicates on certain columns.
For example, the majority of the time, the CBO chooses an INDEX UNIQUE SCAN on a primary key index, but for certain column values it will choose a less efficient INDEX RANGE SCAN on another index which contains the same leading columns contained within the primary key index.
SQLT report shows in Observation Section:
10053 trace will show:
Note: Buckets (Number of histograms) is less than NDV(Number of Distinct Values) for Frequency Histogram
To view full details, sign in with your My Oracle Support account.
Don't have a My Oracle Support account? Click to get started!
In this Document