_optimizer_nlj_hj_adaptive_join in oracle 19.3

 _optimizer_nlj_hj_adaptive_join in oracle 19.3

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Symptoms

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After upgrade to oracle 19.x running a complex query with nested joins can fail with the following error:

ORA-07445: exception encountered: core dump [qkacco()+91] [SIGSEGV]

The Call Stack Trace in the associated incident trace file shows:

   ... qkacco <- qkajoi <- qkaqkn <- qkadrv ...

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Solution

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Upgrade to oracle 19.10

Or

ALTER SESSION SET "_optimizer_nlj_hj_adaptive_join"=FALSE;

Per oracle Technote ORA-7445 [qkacco] when Running a Complex Query with Nested Joins (Doc ID 2664281.1)

Other steps to try are:

  1) "_optimizer_nlj_hj_adaptive_join"=FALSE;  The queries will not use adaptive join features.
  -OR-
  2) optimizer_adaptive_plans=FALSE;  The optimizer will not create adaptive plans.
  -OR-
  3) optimizer_features_enable = '11.2.0.4';    Optimizer features are run as they were in 11.2, avoiding this error.