使用Oracle java JDBC(ojdbc14 10.2.x),加载具有多行的查询需要永久(高延迟环境,这显然是Oracle JDBC中的默认预取是默认大小“10”,这要求每10行的往返时间一次。我试图建立一个积极的预取大小,以避免这一点。Oracle JDBC预取:如何避免RAM耗尽
PreparedStatement stmt = conn.prepareStatement("select * from tablename");
statement.setFetchSize(10000);
ResultSet rs = statement.executeQuery();
这可以工作,而是我得到一个内存不足的异常。我有假设setFetchSize会告诉它在进入时缓冲“那么多行”,并使用每行所需的RAM数量。如果我使用50个线程运行,即使是16G的-XMX空间,它也会耗尽内存。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)
....
我能做些什么仍然可以预取但不会耗尽内存?到底是怎么回事?
上SO与最接近相关的项目是这样的:https://stackoverflow.com/a/14317881/32453