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Archives of the TeradataForum
Message Posted: Wed, 14 Oct 2009 @ 10:11:03 GMT
| Subj: | | Re: Stats not being used by optimizer |
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| From: | | Dieter Noeth |
prahlad.k.patidar wrote:
| | We have a complex query running against Teradata 12. | |
| | When I see explain plan for this after running diagnostic helpstats on for session, it recommends certain sets of collumns for stats
collection but stats for all those columns exists. | |
| | Still why is it giving these recommendation? All stats are up to date. | |
There was a problem with helpstats recommending existing stats. But i think this should have been fixed already.
| | What could be reason, it optimizer not reading stats properly? if so then can we say stats collected on columns used by joins and
where clause do not always help. | |
If the optimizer can't use existing stats (e.g. because there's a calculation on that column ) the confidence level will go down to "no
confidence".
Dieter
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