Home Page for the TeradataForum
 

Archives of the TeradataForum

Message Posted: Sat, 06 Oct 2001 @ 11:42:59 GMT


     
  <Prev Next>  
<<First
<Prev
Next> Last>>  


Subj:   Join question
 
From:   Anomy Anom

<-- Anonymously Posted: Thursday, October 04, 2001 14:23 ->

I'm not a join expert so I'm baffled about this.

ni_cktid is non-unique PI of circuit, clli_cd is unique PI of location Why is step 2 distributing this to all-amps and causing an all- amps join in step 3? I thought this would be a 2-amp join.

replace macro a_kcr046
  (  ni_cktid     (integer),
     ckt_date     (integer),
     ckt_time     (integer)
   )
as (
  select clli_cd, lata_cd (char(3))
    from location
    where circuit.ni_cktid = :ni_cktid and
          circuit.ckt_date = :ckt_date and
          circuit.ckt_time = :ckt_time and
          circuit.msg_loc_offa = location.clli_cd;
   );

Explanation
--------------------------------------------------
 
  1)First, we lock CORPDBP1.LOCATIONT for access, and we lock corpdbp1.CIRCUITT for access.  
  2)Next, we do a single-AMP RETRIEVE step from corpdbp1.CIRCUITT by way of the primary index "corpdbp1.CIRCUITT.NI_CKTID = 1" with a residual condition of ("(corpdbp1.CIRCUITT.CKT_TIME = 1) AND (corpdbp1.CIRCUITT.CKT_DATE = 1)") into Spool 2, which is redistributed by hash code to all AMPs. Then we do a SORT to order Spool 2 by row hash. The size of Spool 2 is estimated with low confidence to be 16 rows. The estimated time for this step is 0.03 seconds.  
  3)We do an all-AMPs JOIN step from CORPDBP1.LOCATIONT by way of a RowHash match scan with no residual conditions, which is joined to Spool 2 (Last Use). CORPDBP1.LOCATIONT and Spool 2 are joined using a merge join, with a join condition of ("CORPDBP1.LOCATIONT.CLLI_CD = Spool_2.MSG_LOC_OFFA"). The result goes into Spool 1, which is built locally on the AMPs. The size of Spool 1 is estimated with index join confidence to be 16 rows. The estimated time for this step is 0.63 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 0.66 seconds.  



     
  <Prev Next>  
<<First
<Prev
Next> Last>>  
 
 
 
 
 
 
 
 
  
  Top Home Privacy Feedback  
 
 
Copyright for the TeradataForum (TDATA-L), Manta BlueSky    
Copyright 2016 - All Rights Reserved    
Last Modified: 27 Dec 2016