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Message Posted: Wed, 27 Jan 2016 @ 14:49:57 GMT

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Subj:   Re: PI hashing while moving data between tables
From:   Myrna, James

Question was:

While moving data between two tables having the same PI via Insert/Select, does TD Optimizer hash the values on PI again while inserting data into the target table? Or does TD move the data AMP-Locally and does not rehash the values ?


If you run an Explain you can see that the data is AMP local, there is no data redistribution.

          3) We do an all-AMPs RETRIEVE step from xxxxxxxxx by
               way of an all-rows scan with no residual conditions into Spool 1
               (all_amps) (compressed columns allowed), which is built locally on
               the AMPs.  The input table will not be cached in memory, but it is
               eligible for synchronized scanning.  The result spool file will
               not be cached in memory.

            4) We do an all-AMPs MERGE into xxxxxxxx from Spool
               1 (Last Use).



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