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玩Oracle的人都在关注shared pool。 特别是62616964757 a 686964616 Fe 78988 e69 d 8331336563938 library cache,在使用绑定变量(预编译sql )后,确实可以获得很大的性能提升。 目前,转移到Mysql后,特别是innodb,很多东西还可以和Oracle核对。 例如,innodb_buffer_pool_size类似于Oracle的database buffer cache,innnodb_log_buffer,但是inodb _ additional _ size 那有问题。 在Mysql中使用预编译的sql会提高性能吗?
这里我试着在Java的jdbc上进行了测试。 分别在语句和优先级语句上运行了1000个sql,执行了10次
使用语句进行硬分析:
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; 910公共类地址{ 1112私有状态工作器() {13 Date begin=new Date;
415 string driver=' com.MySQL.JDBC.driver '; 1617 string URL=' JDBC : MySQL ://172.16.2.733603306/testdb '; 18 19 connection conn=空; 20状态stmt=null; 21 resultset RS=空; 2223try{24class.forname(driver ); 25 conn=driver manager.getconnection (URL,' dbaadmin ',' 123456 ' ); 26 stmt=conn.createStatement (; 27字符串SQL; 28for(intI=1; i=5000; I ) 29 SQL=' select * from test1 where id=' I; 30RS=stmt.executequery(SQL; 31 } 32 } 33 catch (sqlexception|classnotfoundexceptione ) {34 e.printStackTrace ); 35 ) 3637if(STMT!=null6538try6539stmt.close (; 40}41catch(sqlexceptione ) {42 e.printStackTrace ); 43(44 ) 4546if ) Conn!=null () 47try ) 48Conn.close ); 49}50catch(sqlexceptione ) {51 e.printStackTrace ); 52 ) 53 ) 5455dateend=newdate (;
56 return end.gettime (-begin.gettime ); 57 ) 5859 publicstaticvoidmain (string [ ] args ) 60//todo auto-generatedmethodstub 6162 long elapsed,average; 63 average=0; 64for(intI=1; i=10; I({65El} )
apsed=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 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 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。