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Message Posted: Thu, 01 Nov 2012 @ 12:52:47 GMT

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Subj:   Re: Question on soft "RI" in Teradata
From:   Koushik Chandra

Hi Vincent,

Thanks for the example.

Could you also please let me know that the following explain plan will be same or not, if the RI is HARD RI instead of SOFT RI.

  1)First, we lock a distinct TESTDB."pseudo table" for read on a RowHash to prevent global deadlock for TESTDB.c.  
  2)Next, we lock TESTDB.c for read.  
  3)We do an all-AMPs RETRIEVE step from TESTDB.c by way of an all-rows scan with a condition of ("NOT (TESTDB.c.col1 IS NULL)") into Spool 1 (all_amps), which is built locally on the AMPs. The size of Spool 1 is estimated with low confidence to be 48 rows (1,776 bytes). The estimated time for this step is 0.01 seconds.  
  4)Finally, we send out an END TRANSACTION step to all AMPs involved in processing the request.  
  ->The contents of Spool 1 are sent back to the user as the result of statement 1. The total estimated time is 0.01 seconds.  


Koushik Chandra
IBM India Private Ltd.

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