为什么MySQL 5.1.56中的MySQL查询速度如此之慢？

以下查询在MySQL 5.0.67中以0.3秒的时间执行，在MySQL 5.1.56中以3.0秒的时间执行。为什么在以后的版本中速度要慢十倍

（数据库从5.0.67导出并导入到5.1.56中，因此结构相同。）

5.1.61的产品表

Action  Keyname Type    Unique  Packed  Column  Cardinality Collation   Null    Comment
 Edit    Drop   PRIMARY BTREE   Yes No  product_id  493078  A       
 Edit    Drop   shop_id BTREE   Yes No  shop_id 0   A       
link    493078  A   
 Edit    Drop   title_2 BTREE   Yes No  title   0   A       
image   493078  A   
 Edit    Drop   brand   BTREE   No  No  brand   123269  A   YES 
 Edit    Drop   title   BTREE   No  No  title   493078  A       
 Edit    Drop   date    BTREE   No  No  date    41089   A       
 Edit    Drop   shop_id_2   BTREE   No  No  shop_id 12026   A       
 Edit    Drop   product_id  BTREE   No  No  product_id  493078  A       
date    493078  A   
 Edit    Drop   shop_id_3   BTREE   No  No  shop_id 12026   A       
date    49307   A   
 Edit    Drop   sale_date   BTREE   No  No  sale_date   5940    A

商店表5.0.67

Keyname Type    Cardinality Action  Field
PRIMARY  PRIMARY     502437              product_id
shop_id  UNIQUE  502437              shop_id
link
title_2  UNIQUE  502437              title
image
brand    INDEX   38649           brand
title    INDEX   251218              title
date     INDEX   125609              date
shop_id_2    INDEX   87              shop_id
product_id   INDEX   502437              product_id
date
shop_id_3    INDEX   125609              shop_id
date
sale_date    INDEX   187             sale_date

 Keyname    Type    Cardinality Action  Field
PRIMARY  PRIMARY     163             shop_id

Keyname Type    Cardinality Action  Field
product_id_2     UNIQUE  506094              product_id
sex
product_id   INDEX   506094              product_id

商店表5.161

Action  Keyname Type    Unique  Packed  Column  Cardinality Collation   Null    Comment
 Edit    Drop   PRIMARY BTREE   Yes No  shop_id 163 A

5.0.67的性别表

Keyname Type    Cardinality Action  Field
PRIMARY  PRIMARY     502437              product_id
shop_id  UNIQUE  502437              shop_id
link
title_2  UNIQUE  502437              title
image
brand    INDEX   38649           brand
title    INDEX   251218              title
date     INDEX   125609              date
shop_id_2    INDEX   87              shop_id
product_id   INDEX   502437              product_id
date
shop_id_3    INDEX   125609              shop_id
date
sale_date    INDEX   187             sale_date

 Keyname    Type    Cardinality Action  Field
PRIMARY  PRIMARY     163             shop_id

Keyname Type    Cardinality Action  Field
product_id_2     UNIQUE  506094              product_id
sex
product_id   INDEX   506094              product_id

5.1.61的性别表

Action  Keyname Type    Unique  Packed  Column  Cardinality Collation   Null    Comment
 Edit    Drop   product_id_2    BTREE   Yes No  product_id  0   A       
sex 496732  A   
 Edit    Drop   product_id  BTREE   No  No  product_id  496732  A

MySQL 5.1.61的my.cnf文件

[mysqladmin]
user=username

[mysqld]
basedir=/opt/bitnami/mysql
datadir=/opt/bitnami/mysql/data
port=3306
socket=/opt/bitnami/mysql/tmp/mysql.sock
tmpdir=/opt/bitnami/mysql/tmp

character-set-server=UTF8
collation-server=utf8_general_ci

max_allowed_packet=16M
wait_timeout = 120
long_query_time = 1
log_slow_queries
log_queries_not_using_indexes
query_cache_limit=2M
query_cache_type=1
query_cache_size=8M
innodb_additional_mem_pool_size=8M
innodb_buffer_pool_size=16M
#innodb_log_file_size=128M
#tmp_table_size=64M
#max_connections = 2500
#max_user_connections = 2500
#innodb_flush_method=O_DIRECT
#key_buffer_size=64M

[mysqld_safe]
mysqld=mysqld.bin

[client]
default-character-set=UTF8
port=3306
socket=/opt/bitnami/mysql/tmp/mysql.sock

[manager]
port=3306
socket=/opt/bitnami/mysql/tmp/mysql.sock
pid-file=/opt/bitnami/mysql/tmp/manager.pid
default-mysqld-path=/opt/bitnami/mysql/bin/mysqld.bin

我注意到，如果删除用于添加行号的外部查询，则时差将降至0.3秒，而不是0.7秒

SELECT shop, shops.shop_id AS
shop_id, p1.product_id AS product_id
    FROM products p1
    INNER JOIN sex ON
    sex.product_id=p1.product_id AND
    sex.sex=0 AND
    sex.date >= (SUBDATE(NOW(),INTERVAL 7 DAY)) INNER JOIN
    shops ON
    shops.shop_id = p1.shop_id 

    ORDER BY shop

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尝试使用索引(http://dev.mysql.com/doc/refman/5.1/en/index-hints.html)在中，以及尝试找到使用索引的正确顺序的经验。在大型查询中，mysql通常很难找到正确的索引来使用。

新数据库中的一些索引显示基数0，而在旧数据库中，它们显示的值很大。这可能意味着新数据库对索引的效率有错误的认识。分析该表会更新关于该表所包含的值的信息，以便数据库知道要选择哪个索引

跑

每一张桌子。或者，可以使用单个命令分析所有表：

ANALYZE TABLE products, shops, ...

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参考：

索引导出/导入是否正确/完全正确？在DBs和Compare上运行

EXPLAIN SELECT…

是否使用相同的

mysql.ini

文件？表类型是什么？InnoDb是较新版本中的默认值，而MyISAM以前是默认值。@MitchWheat感谢您提醒我添加了解释计划。

ANALYZE TABLE products, shops, ...