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Archives of the TeradataForum
Message Posted: Thu, 27 Dec 2012 @ 20:05:53 GMT
| Subj: | | Re: Maximum number of foreign key in a table in Teradata? |
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| From: | | frank.c.martinez |
If you put on 32 secondaries, I can guarantee that the optimizer will never use some, and will probably never use most of them. I think if you
ran a poll of the people on this list, you'd find not a lot of use of secondary indices. Somebody asked about Teradata architecture, and one of
the aspects of that is, a secondary index won't be used if more than a certain amount of a particular table (is it 10% or 20%?) of the table is
used. Because a full table scan is faster (think about that for a minute). And with PPI on a larger table, you can do a full scan of a small
partition in a large table much quicklier.
iv
PS: And Dieter, you never weighed in on that skewing thing. You must have better distribution queries than me. Ok, than I.
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