|
|
Archives of the TeradataForum
Message Posted: Fri, 19 Jan 2001 @ 14:48:46 GMT
Subj: | | Re: Unique Value Algorithm |
|
From: | | David Wellman |
Claybourne,
All of the OLAP functions generate the "all-AMP STAT function" step which will cause a redistribution (in fact two I think, one to
distribute by value and then a second one to get it back to the correct AMP ready for the merge into the target table). This may well be a
downside of using CSUM to generate sequential numbers.
However, bear in mind that the hashrow function may not generate unique values even with unique 'input' data values. I'm thinking back
to your initial email on this subject. This may be especially true when you're dealing with three integers as your input columns (do they
contain overlapping ranges of values - this'll just make it worse). But there again unique values may not be an absolute requirement for
you.
Regards,
Dave
| |