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From "Hubert Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HAWQ-850) Planner supports refineCachedPlan interface.
Date Wed, 22 Jun 2016 03:15:58 GMT
Hubert Zhang created HAWQ-850:
---------------------------------

             Summary: Planner supports refineCachedPlan interface.
                 Key: HAWQ-850
                 URL: https://issues.apache.org/jira/browse/HAWQ-850
             Project: Apache HAWQ
          Issue Type: Improvement
          Components: Core
            Reporter: Hubert Zhang
            Assignee: Lei Chang


in PBE(prepare bind execution) cases, plan will be cached, and only be generated once in postgres.
But in HAWQ since resource is dynamic or elastic, the plan maybe changed during the different
execution of PBE. Also, the file split allocation result which is stored in plan is dynamically
too, so the split-vseg mapping may also be changed.

For example, We call a plpgsql function which do "insert into t select * from t".
in Prepare we cache the plan, with fixed split-vseg mapping(e.g. 10 blocks), but after insert,
there would be 20 blocks so the old  split-vseg mapping is invalid. We need to update it.
Also when we call this function again and again, the data size of t may request more resource
to handle it than the first call, so we should recalculate the entire plan with the new vseg
number.

This function is implemented in a interface called refineCachedPlan.



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