RE: Count(*) not doing a FTS??
- From: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 2 Sep 2004 16:04:39 -0400
I think your instructor needs to go back to school.
A count(*) may or may not do an FTS. It may do a=20
fast full index scan on a primary key index.
There may be other paths available to it. But,
reading the segment header is not an option.
Ask him: "If what you say is true, shouldn't
it take the same amount of time to do a count(*)
on any table, regardless of the size?"
-Mark
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of rjamya
Sent: Thursday, September 02, 2004 11:21 AM
To: Oracle Discussion List
Subject: Count(*) not doing a FTS??
I am sitting in a class and instructor told us that count(*) reads
rowcount from segment header in some (or most?) cases rather than
doign the good ol' FTS. He can't remember exact details, so this email
....
is it true? Which version was this introduced? Someone has a
reproducible test case?
Thanks in advance
Raj
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