Query with Analytic Windowing Function, Such as ROW_NUMBER OVER PARTITION BY, is Slower in Release 12.1.0.2 (Doc ID 2118138.1)

Last updated on MAY 10, 2016

Applies to:

Oracle Database - Enterprise Edition - Version 12.1.0.2 and later
Information in this document applies to any platform.

Symptoms

On 12.1.0.2, a query containing an analytic windowing function (such as ROW_NUMBER () OVER PARTITION BY) is performing poorly.  Following is an example:

Notice how the cardinality estimate at line one has changed from one to 77,330.

Changes

There may have been a recent upgrade to Oracle Database Release 12.1.0.2.  The performance of the query is worse now than it was on the prior release.

Cause

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