List:Internals« Previous MessageNext Message »
From:Sergei Golubchik Date:January 9 2011 3:41pm
Subject:Re: Optimization about count(*)
View as plain text  
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(*).

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