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Re: CBO cost and avg_row_len

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Thu, 10 Jul 2003 21:16:39 +0100
Message-ID: <bekhhj$jvg$1$8302bc10@news.demon.co.uk>

I haven't checked yet how Oracle estimates the row size of rows that go into the hash (build) table of a hash join. Perhaps the avg_row_length is used as a guideline at this point.

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"Mark D Powell" <Mark.Powell_at_eds.com> wrote in message
news:2687bb95.0307100541.10a6a305_at_posting.google.com...

>
> First, I am not sure when avg_row_len is used, but I believe that
all
> statistics gathered by dbms_stats, unlike some of those gathered by
> the analyze commad (such as chained rows), are used by the CBO. The
> use may be indirect in that some statistics may be used in
calculating
> other statistics that are directly used. For some reason I think
the
> use of avg_row_len is in estimating logical IO, but I would not bank
> on that.
>
Received on Thu Jul 10 2003 - 15:16:39 CDT

Original text of this message

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