mysql300万数据查询500多秒如何优化

mysql 300万数据查询500多秒怎么优化啊
本帖最后由 dz215136304 于 2013-08-15 11:33:52 编辑

linux下 mysql 300万数据查询500多秒怎么优化啊，其中pid已经做索引,id是主键


SELECT id,pid,keyWords,shortUrl FROM keywords WHERE pid=0 ORDER BY id DESC LIMIT 50






explain 如下：

mysql> explain SELECT id,pid,keyWords,shortUrl FROM  keywords  WHERE pid=0 ORDER BY id DESC LIMIT 50;

+----+-------------+----------+------+---------------+------+---------+-------+---------+-----------------------------+

| id | select_type | table    | type | possible_keys | key  | key_len | ref   | rows    | Extra                       |

+----+-------------+----------+------+---------------+------+---------+-------+---------+-----------------------------+

|  1 | SIMPLE      | keywords | ref  | pid           | pid  | 4       | const | 2452523 | Using where; Using filesort |

+----+-------------+----------+------+---------------+------+---------+-------+---------+-----------------------------+

1 row in set (8.18 sec)

另外mysql cpu占用很高怎么回事？内存:512M

配置文件如下：

# Example MySQL config file for small systems.

#

# This is for a system with little memory (<= 64M) where MySQL is only used

# from time to time and it's important that the mysqld daemon

# doesn't use much resources.

#

# You can copy this file to

# /etc/my.cnf to set global options,

# mysql-data-dir/my.cnf to set server-specific options (in this

# installation this directory is /usr/local/mysql/var) or

# ~/.my.cnf to set user-specific options.

#

# In this file, you can use all long options that a program supports.

# If you want to know which options a program supports, run the program

# with the "--help" option.



# The following options will be passed to all MySQL clients

[client]

#password	= your_password

port		= 3306

socket		= /tmp/mysql.sock



# Here follows entries for some specific programs



# The MySQL server

[mysqld]

port		= 3306

socket		= /tmp/mysql.sock

skip-locking

key_buffer = 16K

max_allowed_packet = 1M

table_cache = 4

sort_buffer_size = 64K

read_buffer_size = 256K

read_rnd_buffer_size = 256K

net_buffer_length = 2K

thread_stack = 64K

datadir=/www/mysql/data

log-slow-queries=/www/log/mysql/slowquery.log

long_query_time=2





# Don't listen on a TCP/IP port at all. This can be a security enhancement,

# if all processes that need to connect to mysqld run on the same host.

# All interaction with mysqld must be made via Unix sockets or named pipes.

# Note that using this option without enabling named pipes on Windows

# (using the "enable-named-pipe" option) will render mysqld useless!

# 

#skip-networking

server-id	= 1



# Uncomment the following if you want to log updates

#log-bin=mysql-bin



# Uncomment the following if you are NOT using BDB tables

#skip-bdb



# Uncomment the following if you are using InnoDB tables

#innodb_data_home_dir = /usr/local/mysql/var/

#innodb_data_file_path = ibdata1:10M:autoextend

#innodb_log_group_home_dir = /usr/local/mysql/var/

#innodb_log_arch_dir = /usr/local/mysql/var/

# You can set .._buffer_pool_size up to 50 - 80 %

# of RAM but beware of setting memory usage too high

#innodb_buffer_pool_size = 16M

#innodb_additional_mem_pool_size = 2M

# Set .._log_file_size to 25 % of buffer pool size

#innodb_log_file_size = 5M

#innodb_log_buffer_size = 8M

#innodb_flush_log_at_trx_commit = 1

#innodb_lock_wait_timeout = 50



[mysqldump]

quick

max_allowed_packet = 16M



[mysql]

no-auto-rehash