Re: RE: Dead slow count(*)

  • From: <ryan.gaffuri@xxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Mon, 9 Feb 2004 16:58:57 -0500

number of extents does not matter in a query. common myth. I think there is a 
paper from about 5 years ago with common myths in it and that was one of them. 
Could be wrong. 

high water only matters if your not using an index. 
> 
> From: "M Rafiq" <rafiq9857@xxxxxxxxxxx>
> Date: 2004/02/09 Mon PM 04:40:03 EST
> To: oracle-l@xxxxxxxxxxxxx
> Subject: RE: Dead slow count(*)
> 
> Possible reasons may be
> 
> 1) large number of extents
> 2)Very high 'high water mark) on table...
> 
> Regards
> Rafiq
> 
> 
> 
> 
> 
> From: "Ron Rogers" <RROGERS@xxxxxxxxxxxxx>
> Reply-To: oracle-l@xxxxxxxxxxxxx
> To: <oracle-l@xxxxxxxxxxxxx>
> Subject: RE: Dead slow count(*)
> Date: Mon, 09 Feb 2004 16:08:28 -0500
> 
> Jordi,
>   4 hours for a 4mil table sounds like you have other problems in the
> system or setup. what is the size of your sga, pga, system memory, swap
> size. they all play into the factor.
> 
> RedHat 7.2  752meg ram
> Oracle 8.1.7.5
> 
> set timing on
> select count(*) from large table;
> count(*) 3,500,000 rows;
> Elapsed 00.00:05.23
> 
> Ron
> 
>  >>> jbredsh@xxxxxxx 02/09/2004 1:16:11 PM >>>
> 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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