Пренаписване на mysql select за намаляване на времето и запис на tmp на диск

надявам се да намерите това за полезно - http://pastie.org/1105206

drop table if exists poster;
create table poster
(
poster_id int unsigned not null auto_increment primary key,
name varchar(255) not null unique
)
engine = innodb; 


drop table if exists category;
create table category
(
cat_id mediumint unsigned not null auto_increment primary key,
name varchar(255) not null unique
)
engine = innodb; 

drop table if exists poster_category;
create table poster_category
(
cat_id mediumint unsigned not null,
poster_id int unsigned not null,
primary key (cat_id, poster_id) -- note the clustered composite index !!
)
engine = innodb;

-- FYI http://dev.mysql.com/doc/refman/5.0/en/innodb-index-types.html

select count(*) from category
count(*)
========
500,000


select count(*) from poster
count(*)
========
1,000,000

select count(*) from poster_category
count(*)
========
125,675,688

select count(*) from poster_category where cat_id = 623
count(*)
========
342,820

explain
select
 p.*,
 c.*
from
 poster_category pc
inner join category c on pc.cat_id = c.cat_id
inner join poster p on pc.poster_id = p.poster_id
where
 pc.cat_id = 623
order by
 p.name
limit 32;

id  select_type table   type    possible_keys   key     key_len ref                         rows
==  =========== =====   ====    =============   ===     ======= ===                         ====
1   SIMPLE      c       const   PRIMARY         PRIMARY 3       const                       1   
1   SIMPLE      p       index   PRIMARY         name    257     null                        32  
1   SIMPLE      pc      eq_ref  PRIMARY         PRIMARY 7       const,foo_db.p.poster_id    1   

select
 p.*,
 c.*
from
 poster_category pc
inner join category c on pc.cat_id = c.cat_id
inner join poster p on pc.poster_id = p.poster_id
where
 pc.cat_id = 623
order by
 p.name
limit 32;

Statement:21/08/2010 
0:00:00.021: Query OK