Re: RE: Dead slow count(*)
- From: <ryan.gaffuri@xxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Mon, 9 Feb 2004 14:00:40 -0500
you wont. count(1) and count(*) are exactly the same thing. its a common myth.
guy needs to run the explain plan and see what happens. remember to analyze the
table with cascade=>true after adding the index.
fastest way to do a count is with a bitmap index. It runs in a fraction of the
time of a btree index. cant do this if its a transactional table.
>
> From: "Cary Millsap" <cary.millsap@xxxxxxxxxx>
> Date: 2004/02/09 Mon PM 01:52:11 EST
> To: <oracle-l@xxxxxxxxxxxxx>
> Subject: RE: Dead slow count(*)
>
> I think Oracle will use an index to perform count(*) as well. ...If
> there exists an index with at least one NOT NULL column in its key.
>
> In other words, I don't think you'll find a difference between the
> performance of count(*) and count(1). But try it. :)
>
> (Thanks, Connor!)
>
>
> Cary Millsap
> Hotsos Enterprises, Ltd.
> http://www.hotsos.com
> * Nullius in verba *
>
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>
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx
> [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Jonathan Redshaw
> Sent: Monday, February 09, 2004 12:16 PM
> To: oracle-l@xxxxxxxxxxxxx
> Subject: RE: Dead slow count(*)
>
> I received this tip in a PL/SQL class. On large table you can use
> count(1)
> to force use of the index. I have not verified this but it may help.
>
>
> >From: Jordi Adame V <jordi@xxxxxxxxxxxx>
> >Reply-To: oracle-l@xxxxxxxxxxxxx
> >To: Oracle-L@xxxxxxxxxxxxx
> >Subject: Dead slow count(*)
> >Date: Thu, 29 Jan 2004 17:54:46 -0600
> >
> >Hi!
> >
> >I have this table with ~4,000,000 entries
> >
> >When i do a SELECT COUNT(*) FROM TABLE_NAME
> >
> >it takes 4 hours to give me the result, this is way too much
> >
> >Im running Oracle 9.2.0.4.0 on RedHat AS 3
> >
> >These are my first experiences with Oracle, so I have no clue how to
> fix
> >this
> >query time... Any help would be nice
> >
> >regards
> >
> >Jordi
> >
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