使用Oracle java JDBC(ojdbc14 10.2.x),加載具有多行的查詢需要永久(高延遲環境,這顯然是Oracle JDBC中的默認預取是默認大小「10」,這要求每10行的往返時間一次。我試圖建立一個積極的預取大小,以避免這一點。Oracle JDBC預取:如何避免RAM耗盡
PreparedStatement stmt = conn.prepareStatement("select * from tablename");
statement.setFetchSize(10000);
ResultSet rs = statement.executeQuery();
這可以工作,而是我得到一個內存不足的異常。我有假設setFetchSize會告訴它在進入時緩衝「那麼多行」,並使用每行所需的RAM數量。如果我使用50個線程運行,即使是16G的-XMX空間,它也會耗盡內存。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)
....
我能做些什麼仍然可以預取但不會耗盡內存?到底是怎麼回事?
上SO與最接近相關的項目是這樣的:https://stackoverflow.com/a/14317881/32453