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Archives of the TeradataForum
Message Posted: Wed, 04 Aug 2004 @ 09:09:23 GMT
| Subj: | | Re: Sampling of Pages |
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| From: | | Victor Sokovin |
Stephan,
My own background with DB2 is next to zero but based on the description of pages you have provided I would think that the Teradata principle of
proportional sampling is pretty close to that used by DB2. At least as the mathematical statistics is concerned. Instead of simple sampling a
stratified version is used. In case of DB2 it's based on pages; in case of TD it's the AMPs. Proportional samples will most likely not be robust
to chi-square (you could probably measure that and compare to what you have on DB2, if you need to) but the I/O is significantly reduced. You are
right about AMPs as the entities representing parallelism in TD but in this case they have the second function of natural data stratification.
Regards,
Victor
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