RE: Count(*) not doing a FTS??

I think the instructor (in case he/she wasn't joking in the first place)
mixed things up a little here.
I am guessing, but I assume he/she was referring to the fact that the CBO
may use segment header info to estimate the costs of a full table scan in
the absence of table statistics.

well, there is some distinct relationship between the two queries "select
count(*) from T" and "how expensive you think a FTS of table T will be" ...

Kind regards,
Lex.

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-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Steve Rospo
Sent: Friday, September 03, 2004 01:17
To: Oracle Discussion List
Subject: Re: Count(*) not doing a FTS??

Did your instructor say this with a straight face?  There's no such voodoo
as a rowcount in a segment header.  The two ways you can do it are a FTS
or fast full scan of a not null index.

On Thu, 2 Sep 2004, rjamya wrote:

> I am sitting in a class and instructor told us that count(*) reads
> rowcount from segment header in some (or most?) cases ...


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