MERGE Statement poor performance due to use of NESTED LOOPS instead HASH JOIN OUTER because of multiple filter predicates
Last updated on MARCH 14, 2018
Applies to:Oracle Database - Enterprise Edition - Version 220.127.116.11 to 18.104.22.168 [Release 11.2 to 12.2]
Information in this document applies to any platform.
Merge statement cannot use HASH JOIN OUTER when there are multiple filter predicates in the join clause. There is an OR operator between those predicates.
Nested loop join is used instead which makes the statement never ending.
The problem manifests as well with UPDATE and DELETE.
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