RE: Difference between count(1) and count(*)
- From: "Mitchell Baldwin" <Mitchell.Baldwin@xxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 8 Jul 2004 15:51:49 +0100
I thought we all agreed years ago that the optimizer is aware of =
Count(*) ?..
-----Original Message-----
From: Srinivasan Vasan [mailto:Vasan.Srinivasan@xxxxxxxxxxxxx]
Sent: 08 July 2004 15:38
To: 'oracle-l@xxxxxxxxxxxxx'
Subject: RE: Difference between count(1) and count(*)
Is this a difference between RBO and CBO? I am on CBO on 9.2.0.5 and my
timings are similar to Mladen's - i.e., almost the same for all types of
counts.
Cheers,=20
Vasan.
-----Original Message-----
From: Mladen Gogala [mailto:mladen@xxxxxxxxxxxxxxx]=20
Sent: 08 July 2004 15:32
To: oracle-l@xxxxxxxxxxxxx
Subject: Re: Difference between count(1) and count(*)
On 07/08/2004 09:40:17 AM, Peter Miller wrote:
> 1,749,951 rows returned in every case
>=20
> count(rowid) - approx 3.2 secs
> count(obj#) - approx 3.5 secs
> count(1) - approx 3.6 secs
> count(*) - approx 3.6 secs
> count(rownum)- approx 4.6 secs
> count(source)- approx 8.6 secs
>=20
Connected to:
Oracle9i Enterprise Edition Release 9.2.0.5.0 - Production
With the Partitioning option
JServer Release 9.2.0.5.0 - Production
=20
SQL> set timing on
SQL> select count(*) from wi_cumulative;
=20
COUNT(*)
----------
12148659
=20
Elapsed: 00:00:20.16
SQL> select count(rowid) from wi_cumulative;
=20
COUNT(ROWID)
------------
12148659
=20
Elapsed: 00:00:20.62
SQL> select count(1) from wi_cumulative;
=20
COUNT(1)
----------
12148659
=20
Elapsed: 00:00:21.52
SQL> select count(null) from wi_cumulative;
=20
COUNT(NULL)
-----------
0
=20
Elapsed: 00:00:19.12
SQL>
Tanel's favorite way of counting differed from the real count for only =
about
12 million rows,
and it wasn't that much faster, so the difference doesn't justify lack =
of
precision.
--=20
Mladen Gogala
Oracle DBA
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