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Archives of the TeradataForum
Message Posted: Wed, 19 Nov 2003 @ 09:55:36 GMT
| Subj: | | Re: Join Index usage |
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| From: | | Vivek Pandey |
I hope this example will clarify the doubt.
ct t1 ( a int , b int);
create join index j1 as sel b from t1;
create view v1 as locking t1 for access sel b from t1;
explain sel b from v1;
Explanation
-------------------------------------------------- | | 1) First, we lock DR_DWH_LM_GH.J1 for access, and we lock DR_DWH_LM_GH.t1 for access.
2) Next, we do an all-AMPs RETRIEVE step from DR_DWH_LM_GH.J1 by way of an all-rows scan with no residual conditions into Spool 1
(group_amps), which is built locally on the AMPs. The size of Spool 1 is estimated with low confidence to be 10 rows. The estimated time
for this step is 0.56 seconds.
3) 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 0.56 seconds.
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Thanks, Vivek.
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