Home Page for the TeradataForum

Archives of the TeradataForum

Message Posted: Fri, 12 Oct 2001 @ 07:50:08 GMT

  <Prev Next>   <<First <Prev

Subj:   Re: Value Ordered Indexes
From:   David Wellman


600 million rows is a reasonably large table but (as with all things Teradata) whether or not an index is used is down to the optimiser at run time. A couple of questions;

- how many AMPs on your system? i.e. how many rows per AMP for this table? If it's 'too few' (no, I don't have any numbers) then the NUSI is basically never going to be used.

- during your tests, how many rows were estimated to be returned? Again, 'too many' and the NUSI will be rejected in favour of an FTS.

A recent email thread here indicated that anything more than (I think) 2-3% of the table - 12-18 million rows in your case - will mean an FTS. I think this may also be affected by the number of data blocks in the table and hence is affected by the row size.



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