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Message Posted: Mon, 20 Jan 2004 @ 07:08:03 GMT

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Subj:   Re: Query Optimization with Inner Joins
From:   Hough, David A

  4) We execute the following steps in parallel.
       1) We do an all-AMPs RETRIEVE step from DATABASE_1.temp by
          way of an all-rows scan with a condition of ("(NOT
          (DATABASE_1.temp.SESSION_ID IS NULL ))") into Spool 2
          (all_amps), which is redistributed by hash code to all AMPs.
          The size of Spool 2 is estimated with no confidence to be 114
          rows.  The estimated time for this step is 0.03 seconds.

This piece of the join plan is terrible. Try collecting stats on the PI for the small table and try to get the confidence above 'none'. Also consider altering the index and join columns to 'NOT NULL'.

/dave hough

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