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From:sky.jian Date:January 10 2011 1:41am
Subject:Re: Optimization about count(*)
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I think MySQL just need to read the B-Tree index for this count(*).

On 01/09/2011 11:41 PM, Sergei Golubchik wrote:
> Hi, ??????!
>
> On Jan 09, ?????? wrote:
>    
>> sql:
>> select count(*) from t where id>  10 and id<  1000000;
>> In table t, there is an B-tree index on id field, this sql will read
>> hundreds of thousandes of lines from the storage engine, this is a
>> time-consuming operation.
>> If tell the storage engine computing the count in the range, does it
>> have higher performance? (using records_in_range() api and so on)
>>      
> There's no API for that in MySQL yet.
> records_in_range() is approximate, it cannot be used for count(*).
>
> Regards,
> Sergei
>
>    


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Thread
Optimization about count(*)谢立超9 Jan
  • Re: Optimization about count(*)Sergei Golubchik9 Jan
    • Re: Optimization about count(*)sky.jian10 Jan
      • Re: Optimization about count(*)Sergei Golubchik10 Jan