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测试mysql的sql语句预编译效果

来源:未知 IT堂 发布时间:2015-12-23 收藏 投稿 字体:【

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:

复制代码
 1 package exmysql;
 2 
 3 import java.sql.Connection;
 4 import java.sql.DriverManager;
 5 import java.sql.ResultSet;
 6 import java.sql.SQLException;
 7 import java.sql.Statement;
 8 import java.util.Date;
 9 
10 public class adddata {
11     
12     private static long worker(){
13         Date begin = new Date(); 
14         
15         String driver="com.mysql.jdbc.Driver";
16 
17         String url="jdbc:mysql://172.16.2.7:3306/testdb";
18         
19         Connection conn=null;
20         Statement stmt=null;
21         ResultSet rs=null;
22         
23         try{
24             Class.forName(driver);
25             conn=DriverManager.getConnection(url,"dbaadmin","123456");
26             stmt=conn.createStatement();
27             String sql;
28             for (int i=1;i<=5000;i++){
29                 sql="select * from test1 where id="+i;
30                 rs=stmt.executeQuery(sql);
31             }
32         }
33         catch(SQLException | ClassNotFoundException e){
34             e.printStackTrace();
35         }
36         
37         if(stmt!=null){
38             try{
39                 stmt.close();
40             }
41             catch(SQLException e){
42                 e.printStackTrace();
43             }
44         }
45         
46         if(conn!=null){
47             try{
48                 conn.close();
49             }
50             catch(SQLException e){
51                 e.printStackTrace();
52             }
53         }
54         
55         Date end = new Date(); 
56         return end.getTime()-begin.getTime();
57     }
58 
59     public static void main(String[] args) {
60         // TODO Auto-generated method stub
61         
62         long elapsed,average;
63         average=0;
64         for (int i=1;i<=10;i++){
65             elapsed=worker();
66             System.out.println("elapsed time(ms):"+elapsed);
67             average=average+elapsed;
68         }
69         System.out.println("average time(ms):"+average/10);
70     }
71 
72 }
复制代码

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

 

复制代码
 1 package exmysql;
 2 
 3 import java.sql.*;
 4 import java.util.Date;
 5 
 6 public class insert_data {
 7 
 8     private static long worker(){
 9         Date begin = new Date(); 
10         
11         String driver="com.mysql.jdbc.Driver";
12 
13         String url="jdbc:mysql://172.16.2.7:3306/testdb";
14         
15         Connection conn=null;
16         PreparedStatement pstm=null;
17         ResultSet rs=null;
18         
19         try{
20             Class.forName(driver);
21             conn=DriverManager.getConnection(url,"dbaadmin","123456");
22             conn.setAutoCommit(false);
23             String sql="select * from test1 where id=?";
24             pstm=conn.prepareStatement(sql);
25             for(int i=1;i<=5000;i++){
26                 pstm.setInt(1, i);
27                 rs=pstm.executeQuery();
28             }
29             conn.commit();
30             
31         }
32         catch(SQLException | ClassNotFoundException e){
33             e.printStackTrace();
34         }
35         
36         if(pstm!=null){
37             try{
38                 pstm.close();
39             }
40             catch(SQLException e){
41                 e.printStackTrace();
42             }
43         }
44         
45         if(conn!=null){
46             try{
47                 conn.close();
48             }
49             catch(SQLException e){
50                 e.printStackTrace();
51             }
52         }
53         
54         Date end = new Date(); 
55         return end.getTime()-begin.getTime();
56     }
57     
58     public static void main(String[] args) {
59         // TODO Auto-generated method stub
60         
61         long elapsed,average;
62         average=0;
63         for (int i=1;i<=10;i++){
64             elapsed=worker();
65             System.out.println("elapsed time(ms):"+elapsed);
66             average=average+elapsed;
67         }
68         System.out.println("average time(ms):"+average/10);
69     }
70 
71 }
复制代码

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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