jdbc查询超大数据集内存溢出

水深无声 2022-05-15 05:08 258阅读 0赞

今天使用jdbc的PreparedStatement查询语句如下：

1.  Class.forName( "com.mysql.jdbc.Driver" );  
2.          String url = "jdbc:mysql://localhost:3306/translate?characterEncoding=utf8" ;  
3.          String sql = "select id, title, search\_title, content from article" ;  
4.          Connection conn = DriverManager.getConnection(url, "root" ,  "123456" );  
5.          PreparedStatement ps = conn.prepareStatement(sql);  
6.          ResultSet rs = ps.executeQuery();  
7.          rs.close();  
8.          ps.close();  
9.          conn.close();

Class.forName("com.mysql.jdbc.Driver"); String url = "jdbc:mysql://localhost:3306/translate?characterEncoding=utf8"; String sql = "select id, title, search\_title, content from article"; Connection conn = DriverManager.getConnection(url, "root", "123456"); PreparedStatement ps = conn.prepareStatement(sql); ResultSet rs = ps.executeQuery(); rs.close(); ps.close(); conn.close();

总是报这个错误：

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space  
 at com.mysql.jdbc.Buffer.getBytes(Buffer.java:198)  
 at com.mysql.jdbc.Buffer.readLenByteArray(Buffer.java:318)  
 at com.mysql.jdbc.MysqlIO.extractNativeEncodedColumn(MysqlIO.java:3567)  
 at com.mysql.jdbc.MysqlIO.unpackBinaryResultSetRow(MysqlIO.java:3483)  
 at com.mysql.jdbc.MysqlIO.nextRow(MysqlIO.java:1391)  
 at com.mysql.jdbc.MysqlIO.readSingleRowSet(MysqlIO.java:2369)  
 at com.mysql.jdbc.MysqlIO.getResultSet(MysqlIO.java:451)  
 at com.mysql.jdbc.MysqlIO.readResultsForQueryOrUpdate(MysqlIO.java:2076)  
 at com.mysql.jdbc.MysqlIO.readAllResults(MysqlIO.java:1451)  
 at com.mysql.jdbc.ServerPreparedStatement.serverExecute(ServerPreparedStatement.java:1314)  
 at com.mysql.jdbc.ServerPreparedStatement.executeInternal(ServerPreparedStatement.java:740)  
 at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1467)

但是从网上找到的doc说，默认情况下不会出这个问题的，因为java回自动的优化不会导致内存溢出的。百思不得其解。

后来无意找到一个介绍，这么来做

就是给url连接字符串添加2个属性即可：useCursorFetch=true&defaultFetchSize=100