测试mysql的sql语句预编译效果

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：

 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 stub61     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 }

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

 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 stub60     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 }

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。

原标题：测试mysql的sql语句预编译效果

关键词：MYSQL