Identify the reason why the optimizer chose different execution plans.

Examine the parameter for your database instance: You generated the execution plan for
the following query in the plan table and noticed that the nested loop join was done. After
actual execution of the query, you notice that the hash join was done in the execution plan:
Identify the reason why the optimizer chose different execution plans.

Examine the parameter for your database instance: You generated the execution plan for
the following query in the plan table and noticed that the nested loop join was done. After
actual execution of the query, you notice that the hash join was done in the execution plan:
Identify the reason why the optimizer chose different execution plans.

A.
The optimizer used a dynamic plan for the query.

B.
The optimizer chose different plans because automatic dynamic sampling was enabled.

C.
The optimizer used re-optimization cardinality feedback for the query.

D.
The optimizer chose different plan because extended statistics were created for the
columns used.



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Vasya Pupkin

Vasya Pupkin

sorry, C – right

Prisco

Prisco

A is correct, the only resource that changes the plan during the execution are the dynamic plans.
B is wrong, dynamic sampling is only enable if the parameter optimizer_dynamic_sampling is 11.
C is wrong, re-optimization only work on the next execution of the SQL.

CC Noll

CC Noll

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Nitya

Nitya

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