RE: sequential read on full-table scan?

From: Martic Zoran <zoran_martic_at_yahoo.com>
Date: Sun, 22 May 2005 02:32:46 -0700 (PDT)
Message-ID: <20050522093246.70534.qmail@web52608.mail.yahoo.com>

Christian,

Thanks for your good answer.

It is always the balance between good and bad things.

The main idea of my questions is to drive more brains thinking about something possible interesting (at least to me, I hope to others too).

It looks to me that Oracle is waiting for the response from the customer base before trying to figure out what is the best.
I am not sure that they have up to now all intelligence of what will be the best way to progress more with system statistics.  

My main concern is that these statistics should be at least per file basis, but of course if object spans multiple files or object is partitioned it brings you more dimensions.
But as Oracle oversimplified and used avearages for everything why it should not use averages per file basis too, at least for objects belongs to the specific file.

Oh sorry, maybe tablespace level may be even better.

Per object may be very big price to be paid in the level of code and complexity. But not sure that it is crazy hard per tablespace, especially because Oracle has file stats already that can be used to be averaged over tablespaces on which objects are based.

Let's wait what is going to happen in 10g R2 if any :)

At the end the system statistics that are bringing the intelligence about I/O subsystem performances are the key piece in getting proper optimizer COST and good execution plan. Disk I/O are the slowest part of the modern systems so making sure that knowledge about it may be more important then something else.

Regards,
Zoran

• Christian Antognini <Christian.Antognini_at_trivadis.com> wrote:
  > Hi Zoran
  >
  > >The main question is how good is that prediction
  > based
  > >on the global system statistics only.
  > >Not sure how these statistics if collected per file
  > or
  > >object level will be more useful???
  >
  > If you want to have really good statistics you
  > should add either a time =
  > dimension and some kind of forecasting (regression?)
  > or real-time =
  > statistics.
  >
  > Of course both have major problems... e.g.: What
  > about segments that =
  > span more files? What about partitioned objects?
  > When are the cached =
  > execution plans invalidated?=20
  >
  > IMHO it's better to KISS.
  >
  >
  > Just my 2 cents!
  > Chris
  > --
  > http://www.freelists.org/webpage/oracle-l
  >
  

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Received on Sun May 22 2005 - 05:37:28 CDT