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测试mysql的sql语句预编译效果

2016-09-09 11:20 225 查看
手动迁移原创博客,原文发表在http://www.cnblogs.com/paololiu/p/5070737.html

玩Oracle的都比较关注shared pool,特别是library cache,在使用了绑定变量(预编译sql)之后确实能得到很大的性能提升。现在在转Mysql之后特别是innodb很多东西都还能和Oracle对得上号的,就像innodb_buffer_pool_size类似于Oracle的database buffer cache,innodb_log_buffer_size类似于redo log buffer,但是innodb_additional_mem_pool_size仅仅类似于shared
pool的Data dictionary cache,似乎还缺少和library cache相对应的东西。那就有一个问题了,在Mysql里面使用预编译的sql还会有性能提升吗?

这里我用Java的jdbc做了一下测试,分别用Statement和PreparedStatement执行1000个sql,并运行10次

1.使用Statement做硬解析:

package exmysql;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Date;

public class adddata {

private static long worker(){
Date begin = new Date();

String driver="com.mysql.jdbc.Driver";

String url="jdbc:mysql://172.16.2.7:3306/testdb";

Connection conn=null;
Statement stmt=null;
ResultSet rs=null;

try{
Class.forName(driver);
conn=DriverManager.getConnection(url,"dbaadmin","123456");
stmt=conn.createStatement();
String sql;
for (int i=1;i<=5000;i++){
sql="select * from test1 where id="+i;
rs=stmt.executeQuery(sql);
}
}
catch(SQLException | ClassNotFoundException e){
e.printStackTrace();
}

if(stmt!=null){
try{
stmt.close();
}
catch(SQLException e){
e.printStackTrace();
}
}

if(conn!=null){
try{
conn.close();
}
catch(SQLException e){
e.printStackTrace();
}
}

Date end = new Date();
return end.getTime()-begin.getTime();
}

public static void main(String[] args) {
// TODO Auto-generated method stub

long elapsed,average;
average=0;
for (int i=1;i<=10;i++){
elapsed=worker();
System.out.println("elapsed time(ms):"+elapsed);
average=average+elapsed;
}
System.out.println("average time(ms):"+average/10);
}

}

结果如下:

elapsed time(ms):24652

elapsed time(ms):13380

elapsed time(ms):13250

elapsed time(ms):13877

elapsed time(ms):13275

elapsed time(ms):13193

elapsed time(ms):19022

elapsed time(ms):13558

elapsed time(ms):14138

elapsed time(ms):13364

average time(ms):15170

2.同样的sql用PreparedStatement预编译执行

package exmysql;

import java.sql.*;
import java.util.Date;

public class insert_data {

private static long worker(){
Date begin = new Date();

String driver="com.mysql.jdbc.Driver";

String url="jdbc:mysql://172.16.2.7:3306/testdb";

Connection conn=null;
PreparedStatement pstm=null;
ResultSet rs=null;

try{
Class.forName(driver);
conn=DriverManager.getConnection(url,"dbaadmin","123456");
String sql="select * from test1 where id=?";
pstm=conn.prepareStatement(sql);
for(int i=1;i<=5000;i++){
pstm.setInt(1, i);
rs=pstm.executeQuery();
}

}
catch(SQLException | ClassNotFoundException e){
e.printStackTrace();
}

if(pstm!=null){
try{
pstm.close();
}
catch(SQLException e){
e.printStackTrace();
}
}

if(conn!=null){
try{
conn.close();
}
catch(SQLException e){
e.printStackTrace();
}
}

Date end = new Date();
return end.getTime()-begin.getTime();
}

public static void main(String[] args) {
// TODO Auto-generated method stub

long elapsed,average;
average=0;
for (int i=1;i<=10;i++){
elapsed=worker();
System.out.println("elapsed time(ms):"+elapsed);
average=average+elapsed;
}
System.out.println("average time(ms):"+average/10);
}

}


结果如下:

elapsed time(ms):14773

elapsed time(ms):16352

elapsed time(ms):14797

elapsed time(ms):15800

elapsed time(ms):12069

elapsed time(ms):14953

elapsed time(ms):13238

elapsed time(ms):12366

elapsed time(ms):15263

elapsed time(ms):13089

average time(ms):14270

可以看出两种方式执行的结果几乎相同,不像Oracle差距那么大。而且就算是用PreparedStatement的方式,在Mysql数据库端抓出来的sql语句也不是以变量id=?的形式出现的,而是实际的数值。后来在网上看到在连接字符串上加上useServerPrepStmts=true可以实现真正的预编译

String url="jdbc:mysql://172.16.2.7:3306/testdb";
url=url+"?useServerPrepStmts=true";


加上这段后可以在数据库端可以看到明确的结果:

mysql> show global status like 'Com_stmt_prepare';

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

| Variable_name | Value |

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

| Com_stmt_prepare | 11 |

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

1 row in set (0.00 sec)

 

但是实际的运行结果和上面几乎一样,性能上也没有任何的提升。由此可以推断出Mysql由于缺少类似于Oracle的library cache的部件,因此采用预编译方式执行sql是没有性能上的提升的。
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