Re: sane number of the table partitions in DWH
- From: Riyaj Shamsudeen <riyaj.shamsudeen@xxxxxxxxx>
- To: Milen Kulev <makulev@xxxxxxx>
- Date: Wed, 1 Apr 2009 08:39:56 -0500
Hello Milen
>> Partioning pruning is obviously not for free
Of course. I didn't mean that partition pruning is free and my statement
was in the scope of hard parsing only, not execution. Let me clarify this
further:
Let's say that partition count is higher and partition pruning is done
at parse time (meaning use of literal variables on partition keys). Then
during parse time Optimizer must choose the correct partition comparing
boundaries of partitions. My point was that, as long as, your buffer_cache
and shared_pool are decently sized,selection of a partition at parse step is
not costly. Further to the point, rowcache aids hugely for this.
I guess, I should have used the term 'partition selection at parse time'.
Of course, I didn't consider 'partition pruning' at execution time with the
details provided.
Actual, partition pruning at execution step is a completely different
matter :-)
Reposting due to overquoting..
Cheers
Riyaj Shamsudeen
Principal DBA,
Ora!nternals - http://www.orainternals.com
Specialists in Performance, Recovery and EBS11i
Blog: http://orainternals.wordpress.com
>
> >> Partioning pruning is obviously not for free
>
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