org.apache.flink.runtime.operators.util.JoinTaskIterator Maven / Gradle / Ivy
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* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
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package org.apache.flink.runtime.operators.util;
import java.io.IOException;
import org.apache.flink.api.common.functions.FlatJoinFunction;
import org.apache.flink.runtime.memory.MemoryAllocationException;
import org.apache.flink.util.Collector;
/**
* Interface of an iterator that performs the logic of a match task. The iterator follows the
* open/next/close principle. The next logic here calls the match stub with all
* value pairs that share the same key.
*
*/
public interface JoinTaskIterator
{
/**
* General-purpose open method. Initializes the internal strategy (for example triggers the
* sorting of the inputs or starts building hash tables).
*
* @throws IOException Thrown, if an I/O error occurred while preparing the data. An example is a failing
* external sort.
* @throws MemoryAllocationException Thrown, if the internal strategy could not allocate the memory it needs.
* @throws InterruptedException Thrown, if the thread was interrupted during the initialization process.
*/
void open() throws IOException, MemoryAllocationException, InterruptedException;
/**
* General-purpose close method. Works after the principle of best effort. The internal structures are
* released, but errors that occur on the way are not reported.
*/
void close();
/**
* Moves the internal pointer to the next key that both inputs share. It calls the match stub with the
* cross product of all values that share the same key.
*
* @param matchFunction The match stub containing the match function which is called with the keys.
* @param collector The collector to pass the match function.
* @return True, if a next key exists, false if no more keys exist.
* @throws Exception Exceptions from the user code are forwarded.
*/
boolean callWithNextKey(FlatJoinFunction matchFunction, Collector collector) throws Exception;
/**
* Aborts the matching process. This extra abort method is supplied, because a significant time may pass while
* calling the match stub with the cross product of all values that share the same key. A call to this abort
* method signals an interrupt to that procedure.
*/
void abort();
}