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Re: EXPLAIN PLAN

From: Gregory Pucka <puckag_at_sprintmail.com>
Date: 1997/02/05
Message-ID: <32F91E33.5A9A@sprintmail.com>#1/1

Tad Davis wrote:
>
> What percentage do you use when you run ANALYZE with the ESTIMATE option?
> So far I've only gotten one response to that question. Larger samples do
> seem to improve performance, but there must be a point of diminishing
> returns.
>

You should estimate at least 15 to 20%. Anything less then that and you could end up with some skewed statistics. If the percent or the number rows you specify is over 50% Oracle will compute the statistics because there would be very little time savings.

> Second, the manual is clear that when you say ANALYZE TABLE, Oracle
> automatically analyzes the indexes too. I'm relying on that; should I?

The indexes do get analyzed. If you want to check just query the dba_indexes view and you will see the number of distinct keys, blevel, leaf_blocks, ......

>
> --
> Tad Davis 215-898-7864 voice
> (davist_at_isc.upenn.edu) 215-898-0386 fax
 

-- 
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Received on Wed Feb 05 1997 - 00:00:00 CST

Original text of this message

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