相关疑难解决方法(0)

使用Oracle java JDBC(ojdbc14 10.2.x),加载具有多行的查询需要永远(高延迟环境.显然,Oracle JDBC中的默认预取是默认大小"10",这需要每10行一次往返时间.我试图设置一个积极的预取大小,以避免这种情况.

 PreparedStatement stmt = conn.prepareStatement("select * from tablename");
 statement.setFetchSize(10000);
 ResultSet rs = statement.executeQuery();

这可以工作,但我得到一个内存不足的例外.我曾经假设setFetchSize会告诉它在它们进入时缓冲"那么多行",使用每行所需的RAM.如果我运行50个线程,即使使用16G的-XMX空间,它也会耗尽内存.感觉几乎像泄漏:

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at java.lang.reflect.Array.newArray(Native Method)
    at java.lang.reflect.Array.newInstance(Array.java:70)
    at oracle.jdbc.driver.BufferCache.get(BufferCache.java:226)
    at oracle.jdbc.driver.PhysicalConnection.getCharBuffer(PhysicalConnection.java:7422)
    at oracle.jdbc.driver.OracleStatement.prepareAccessors(OracleStatement.java:983)
    at oracle.jdbc.driver.T4CTTIdcb.receiveCommon(T4CTTIdcb.java:273)
    at oracle.jdbc.driver.T4CTTIdcb.receive(T4CTTIdcb.java:144)
    at oracle.jdbc.driver.T4C8Oall.readDCB(T4C8Oall.java:771)
    at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:346)
    at oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:186)
    at oracle.jdbc.driver.T4C8Oall.doOALL(T4C8Oall.java:521)
    at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:205)
    at oracle.jdbc.driver.T4CPreparedStatement.executeForDescribe(T4CPreparedStatement.java:861)
    at oracle.jdbc.driver.OracleStatement.executeMaybeDescribe(OracleStatement.java:1145)
    at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1267)
    at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3449)
    at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:3493)
    at oracle.jdbc.driver.OraclePreparedStatementWrapper.executeQuery(OraclePreparedStatementWrapper.java:1491)
    ....

我还能做些什么来获取预取但不会耗尽RAM？到底是怎么回事？

SO上最接近的相关项目是:https://stackoverflow.com/a/14317881/32453