Adaptive Execution Plan, Invoked from PL/SQL, Slower after Upgrade to 12.2
(Doc ID 2604818.1)
Last updated on DECEMBER 04, 2019
Applies to:Oracle Database - Enterprise Edition - Version 220.127.116.11 to 18.104.22.168 [Release 12.2]
Information in this document applies to any platform.
A query, invoked from a PL/SQL stored procedure, produces an adaptive execution plan which takes far more elapsed time than it had prior to database upgrade.
You notice the presence of the STATISTICS COLLECTOR operation within the execution plan, which lets you know that this is an adaptive plan. You also notice that a NESTED LOOPS operation is present.
The NESTED LOOPS operation does not appear if you set OPTIMIZER_FEATURES_ENABLE, at the session level, back to the release level, prior to upgrade.
You also notice that you cannot reproduce this slowness from SQL*Plus. Only when you invoke the query from the stored procedure does it take far more elapsed time.
You recently upgraded Oracle Database from a prior release.
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