jdbc查询超大数据集内存溢出

今天使用jdbc的PreparedStatement查询语句如下：

 

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();

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

评论

1 楼 isaiahzhong 2012-11-06  

           defaultFetchSize这个意思是说一次性取多少条数据是吗？好像hibernate里面有一个抓取策略，就是用来控制取多少条数据