Recursive Branch Optimizer Changes from 18c
(Doc ID 2749387.1)
Last updated on MARCH 30, 2021
Applies to:Oracle Database - Enterprise Edition - Version 22.214.171.124.0 and later
Information in this document applies to any platform.
Some statements may not complete on 18c when they were working with adequate response in 12c. If the Statement uses Common Table Expression and performs adequately in 12c but not 19c then this may be the problem you are encountering. The execution plan will be different in 19c and cost may also be much higher.
Additionally, if the initialization parameter in 18c for (ALTER SYSTEM SET optimizer_features_enable='126.96.36.199' SCOPE=BOTH; --originally 18.1.0) is set the execution plan may change back to an acceptable one.
An upgrade or change in the Optimizer environment.
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