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From fhue...@apache.org
Subject [1/5] flink git commit: [FLINK-2105] Extract abstract superclass, interface from MergeMatchIterators, KeyGroupedIterators
Date Tue, 04 Aug 2015 22:41:06 GMT
Repository: flink
Updated Branches:
  refs/heads/master 30761572b -> 941ac6dfd


[FLINK-2105] Extract abstract superclass, interface from MergeMatchIterators, KeyGroupedIterators


Project: http://git-wip-us.apache.org/repos/asf/flink/repo
Commit: http://git-wip-us.apache.org/repos/asf/flink/commit/0dc6849a
Tree: http://git-wip-us.apache.org/repos/asf/flink/tree/0dc6849a
Diff: http://git-wip-us.apache.org/repos/asf/flink/diff/0dc6849a

Branch: refs/heads/master
Commit: 0dc6849a594b61a6cad8ee582ca1758f0349a72b
Parents: 3076157
Author: Johann Kovacs <me@jkovacs.de>
Authored: Fri Jul 10 17:21:58 2015 +0200
Committer: Fabian Hueske <fhueske@apache.org>
Committed: Tue Aug 4 21:35:26 2015 +0200

----------------------------------------------------------------------
 .../operators/sort/AbstractMergeIterator.java   | 356 +++++++++++++++++
 .../sort/AbstractMergeMatchIterator.java        | 107 +++++
 .../sort/NonReusingMergeMatchIterator.java      | 382 +-----------------
 .../sort/ReusingMergeMatchIterator.java         | 389 +------------------
 .../flink/runtime/util/KeyGroupedIterator.java  |  31 ++
 .../util/NonReusingKeyGroupedIterator.java      |   2 +-
 .../runtime/util/ReusingKeyGroupedIterator.java |   5 +-
 7 files changed, 517 insertions(+), 755 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/flink/blob/0dc6849a/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/AbstractMergeIterator.java
----------------------------------------------------------------------
diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/AbstractMergeIterator.java b/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/AbstractMergeIterator.java
new file mode 100644
index 0000000..9a61c14
--- /dev/null
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/AbstractMergeIterator.java
@@ -0,0 +1,356 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.runtime.operators.sort;
+
+import org.apache.flink.api.common.functions.FlatJoinFunction;
+import org.apache.flink.api.common.typeutils.TypeComparator;
+import org.apache.flink.api.common.typeutils.TypePairComparator;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.core.memory.MemorySegment;
+import org.apache.flink.runtime.io.disk.iomanager.IOManager;
+import org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable;
+import org.apache.flink.runtime.memorymanager.MemoryAllocationException;
+import org.apache.flink.runtime.memorymanager.MemoryManager;
+import org.apache.flink.runtime.operators.resettable.NonReusingBlockResettableIterator;
+import org.apache.flink.runtime.operators.resettable.SpillingResettableIterator;
+import org.apache.flink.runtime.operators.util.JoinTaskIterator;
+import org.apache.flink.runtime.util.KeyGroupedIterator;
+import org.apache.flink.util.Collector;
+import org.apache.flink.util.MutableObjectIterator;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Iterator;
+import java.util.List;
+
+public abstract class AbstractMergeIterator<T1, T2, O> implements JoinTaskIterator<T1, T2, O> {
+
+	private final Logger LOG = LoggerFactory.getLogger(getClass());
+
+	protected TypePairComparator<T1, T2> pairComparator;
+
+	protected KeyGroupedIterator<T1> iterator1;
+	protected KeyGroupedIterator<T2> iterator2;
+
+	protected final TypeSerializer<T1> serializer1;
+	protected final TypeSerializer<T2> serializer2;
+
+	private final NonReusingBlockResettableIterator<T2> blockIt;    // for N:M cross products with same key
+
+	private final IOManager ioManager;
+	private final MemoryManager memoryManager;
+	private final List<MemorySegment> memoryForSpillingIterator;
+
+	// instances for object reuse
+	protected T1 copy1;
+	protected T1 spillHeadCopy;
+	protected T2 copy2;
+	protected T2 blockHeadCopy;
+
+	public AbstractMergeIterator(MutableObjectIterator<T1> input1, MutableObjectIterator<T2> input2,
+								TypeSerializer<T1> serializer1, TypeComparator<T1> comparator1,
+								TypeSerializer<T2> serializer2, TypeComparator<T2> comparator2,
+								TypePairComparator<T1, T2> pairComparator,
+								MemoryManager memoryManager,
+								IOManager ioManager,
+								int numMemoryPages,
+								AbstractInvokable parentTask) throws MemoryAllocationException {
+		if (numMemoryPages < 2) {
+			throw new IllegalArgumentException("Merger needs at least 2 memory pages.");
+		}
+
+		this.pairComparator = pairComparator;
+		this.serializer1 = serializer1;
+		this.serializer2 = serializer2;
+
+		this.memoryManager = memoryManager;
+		this.ioManager = ioManager;
+
+		this.iterator1 = createKeyGroupedIterator(input1, serializer1, comparator1.duplicate());
+		this.iterator2 = createKeyGroupedIterator(input2, serializer2, comparator2.duplicate());
+
+		final int numPagesForSpiller = numMemoryPages > 20 ? 2 : 1;
+		this.blockIt = new NonReusingBlockResettableIterator<T2>(this.memoryManager, this.serializer2,
+				(numMemoryPages - numPagesForSpiller), parentTask);
+		this.memoryForSpillingIterator = memoryManager.allocatePages(parentTask, numPagesForSpiller);
+	}
+
+	@Override
+	public void open() throws IOException {
+	}
+
+	@Override
+	public void close() {
+		if (this.blockIt != null) {
+			try {
+				this.blockIt.close();
+			} catch (Throwable t) {
+				LOG.error("Error closing block memory iterator: " + t.getMessage(), t);
+			}
+		}
+
+		this.memoryManager.release(this.memoryForSpillingIterator);
+	}
+
+	@Override
+	public void abort() {
+		close();
+	}
+
+	/**
+	 * Calls the <code>JoinFunction#match()</code> method for all two key-value pairs that share the same key and come
+	 * from different inputs. The output of the <code>match()</code> method is forwarded.
+	 * <p>
+	 * This method first zig-zags between the two sorted inputs in order to find a common
+	 * key, and then calls the match stub with the cross product of the values.
+	 *
+	 * @throws Exception Forwards all exceptions from the user code and the I/O system.
+	 * @see org.apache.flink.runtime.operators.util.JoinTaskIterator#callWithNextKey(org.apache.flink.api.common.functions.FlatJoinFunction, org.apache.flink.util.Collector)
+	 */
+	@Override
+	public abstract boolean callWithNextKey(final FlatJoinFunction<T1, T2, O> matchFunction, final Collector<O> collector)
+			throws Exception;
+
+	protected void crossMatchingGroup(Iterator<T1> values1, Iterator<T2> values2, FlatJoinFunction<T1, T2, O> matchFunction, Collector<O> collector) throws Exception {
+		final T1 firstV1 = values1.next();
+		final T2 firstV2 = values2.next();
+
+		final boolean v1HasNext = values1.hasNext();
+		final boolean v2HasNext = values2.hasNext();
+
+		// check if one side is already empty
+		// this check could be omitted if we put this in MatchTask.
+		// then we can derive the local strategy (with build side).
+
+		if (v1HasNext) {
+			if (v2HasNext) {
+				// both sides contain more than one value
+				// TODO: Decide which side to spill and which to block!
+				crossMwithNValues(firstV1, values1, firstV2, values2, matchFunction, collector);
+			} else {
+				crossSecond1withNValues(firstV2, firstV1, values1, matchFunction, collector);
+			}
+		} else {
+			if (v2HasNext) {
+				crossFirst1withNValues(firstV1, firstV2, values2, matchFunction, collector);
+			} else {
+				// both sides contain only one value
+				matchFunction.join(firstV1, firstV2, collector);
+			}
+		}
+	}
+
+	/**
+	 * Crosses a single value from the first input with N values, all sharing a common key.
+	 * Effectively realizes a <i>1:N</i> match (join).
+	 *
+	 * @param val1      The value form the <i>1</i> side.
+	 * @param firstValN The first of the values from the <i>N</i> side.
+	 * @param valsN     Iterator over remaining <i>N</i> side values.
+	 * @throws Exception Forwards all exceptions thrown by the stub.
+	 */
+	private void crossFirst1withNValues(final T1 val1, final T2 firstValN,
+										final Iterator<T2> valsN, final FlatJoinFunction<T1, T2, O> matchFunction, final Collector<O> collector)
+			throws Exception {
+		T1 copy1 = createCopy(serializer1, val1, this.copy1);
+		matchFunction.join(copy1, firstValN, collector);
+
+		// set copy and match first element
+		boolean more = true;
+		do {
+			final T2 nRec = valsN.next();
+
+			if (valsN.hasNext()) {
+				copy1 = createCopy(serializer1, val1, this.copy1);
+				matchFunction.join(copy1, nRec, collector);
+			} else {
+				matchFunction.join(val1, nRec, collector);
+				more = false;
+			}
+		}
+		while (more);
+	}
+
+	/**
+	 * Crosses a single value from the second side with N values, all sharing a common key.
+	 * Effectively realizes a <i>N:1</i> match (join).
+	 *
+	 * @param val1      The value form the <i>1</i> side.
+	 * @param firstValN The first of the values from the <i>N</i> side.
+	 * @param valsN     Iterator over remaining <i>N</i> side values.
+	 * @throws Exception Forwards all exceptions thrown by the stub.
+	 */
+	private void crossSecond1withNValues(T2 val1, T1 firstValN,
+										Iterator<T1> valsN, FlatJoinFunction<T1, T2, O> matchFunction, Collector<O> collector) throws Exception {
+		T2 copy2 = createCopy(serializer2, val1, this.copy2);
+		matchFunction.join(firstValN, copy2, collector);
+
+		// set copy and match first element
+		boolean more = true;
+		do {
+			final T1 nRec = valsN.next();
+
+			if (valsN.hasNext()) {
+				copy2 = createCopy(serializer2, val1, this.copy2);
+				matchFunction.join(nRec, copy2, collector);
+			} else {
+				matchFunction.join(nRec, val1, collector);
+				more = false;
+			}
+		}
+		while (more);
+	}
+
+	private void crossMwithNValues(final T1 firstV1, Iterator<T1> spillVals,
+									final T2 firstV2, final Iterator<T2> blockVals,
+									final FlatJoinFunction<T1, T2, O> matchFunction, final Collector<O> collector) throws Exception {
+		// ==================================================
+		// We have one first (head) element from both inputs (firstV1 and firstV2)
+		// We have an iterator for both inputs.
+		// we make the V1 side the spilling side and the V2 side the blocking side.
+		// In order to get the full cross product without unnecessary spilling, we do the
+		// following:
+		// 1) cross the heads
+		// 2) cross the head of the spilling side against the first block of the blocking side
+		// 3) cross the iterator of the spilling side with the head of the block side
+		// 4) cross the iterator of the spilling side with the first block
+		// ---------------------------------------------------
+		// If the blocking side has more than one block, we really need to make the spilling side fully
+		// resettable. For each further block on the block side, we do:
+		// 5) cross the head of the spilling side with the next block
+		// 6) cross the spilling iterator with the next block.
+
+		// match the first values first
+		T1 copy1 = this.createCopy(serializer1, firstV1, this.copy1);
+		T2 blockHeadCopy = this.createCopy(serializer2, firstV2, this.blockHeadCopy);
+		T1 spillHeadCopy = null;
+
+		// --------------- 1) Cross the heads -------------------
+		matchFunction.join(copy1, firstV2, collector);
+
+		// for the remaining values, we do a block-nested-loops join
+		SpillingResettableIterator<T1> spillIt = null;
+
+		try {
+			// create block iterator on the second input
+			this.blockIt.reopen(blockVals);
+
+			// ------------- 2) cross the head of the spilling side with the first block ------------------
+			while (this.blockIt.hasNext()) {
+				final T2 nextBlockRec = this.blockIt.next();
+				copy1 = this.createCopy(serializer1, firstV1, this.copy1);
+				matchFunction.join(copy1, nextBlockRec, collector);
+			}
+			this.blockIt.reset();
+
+			// spilling is required if the blocked input has data beyond the current block.
+			// in that case, create the spilling iterator
+			final Iterator<T1> leftSideIter;
+			final boolean spillingRequired = this.blockIt.hasFurtherInput();
+			if (spillingRequired) {
+				// more data than would fit into one block. we need to wrap the other side in a spilling iterator
+				// create spilling iterator on first input
+				spillIt = new SpillingResettableIterator<T1>(spillVals, this.serializer1,
+						this.memoryManager, this.ioManager, this.memoryForSpillingIterator);
+				leftSideIter = spillIt;
+				spillIt.open();
+
+				spillHeadCopy = this.createCopy(serializer1, firstV1, this.spillHeadCopy);
+			} else {
+				leftSideIter = spillVals;
+			}
+
+			// cross the values in the v1 iterator against the current block
+
+			while (leftSideIter.hasNext()) {
+				final T1 nextSpillVal = leftSideIter.next();
+				copy1 = this.createCopy(serializer1, nextSpillVal, this.copy1);
+
+
+				// -------- 3) cross the iterator of the spilling side with the head of the block side --------
+				T2 copy2 = this.createCopy(serializer2, blockHeadCopy, this.copy2);
+				matchFunction.join(copy1, copy2, collector);
+
+				// -------- 4) cross the iterator of the spilling side with the first block --------
+				while (this.blockIt.hasNext()) {
+					T2 nextBlockRec = this.blockIt.next();
+
+					// get instances of key and block value
+					copy1 = this.createCopy(serializer1, nextSpillVal, this.copy1);
+					matchFunction.join(copy1, nextBlockRec, collector);
+				}
+				// reset block iterator
+				this.blockIt.reset();
+			}
+
+			// if everything from the block-side fit into a single block, we are done.
+			// note that in this special case, we did not create a spilling iterator at all
+			if (!spillingRequired) {
+				return;
+			}
+
+			// here we are, because we have more blocks on the block side
+			// loop as long as there are blocks from the blocked input
+			while (this.blockIt.nextBlock()) {
+				// rewind the spilling iterator
+				spillIt.reset();
+
+				// ------------- 5) cross the head of the spilling side with the next block ------------
+				while (this.blockIt.hasNext()) {
+					copy1 = this.createCopy(serializer1, spillHeadCopy, this.copy1);
+					final T2 nextBlockVal = blockIt.next();
+					matchFunction.join(copy1, nextBlockVal, collector);
+				}
+				this.blockIt.reset();
+
+				// -------- 6) cross the spilling iterator with the next block. ------------------
+				while (spillIt.hasNext()) {
+					// get value from resettable iterator
+					final T1 nextSpillVal = spillIt.next();
+					// cross value with block values
+					while (this.blockIt.hasNext()) {
+						// get instances of key and block value
+						final T2 nextBlockVal = this.blockIt.next();
+						copy1 = this.createCopy(serializer1, nextSpillVal, this.copy1);
+						matchFunction.join(copy1, nextBlockVal, collector);
+					}
+
+					// reset block iterator
+					this.blockIt.reset();
+				}
+				// reset v1 iterator
+				spillIt.reset();
+			}
+		} finally {
+			if (spillIt != null) {
+				this.memoryForSpillingIterator.addAll(spillIt.close());
+			}
+		}
+	}
+
+
+	protected abstract <T> KeyGroupedIterator<T> createKeyGroupedIterator(MutableObjectIterator<T> input, TypeSerializer<T> serializer, TypeComparator<T> comparator);
+
+	/**
+	 * Copies an instance of the given type, potentially reusing the object passed as the reuse parameter, which may be null.
+	 */
+	protected abstract <T> T createCopy(TypeSerializer<T> serializer, T value, T reuse);
+
+}

http://git-wip-us.apache.org/repos/asf/flink/blob/0dc6849a/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/AbstractMergeMatchIterator.java
----------------------------------------------------------------------
diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/AbstractMergeMatchIterator.java b/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/AbstractMergeMatchIterator.java
new file mode 100644
index 0000000..791494d
--- /dev/null
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/AbstractMergeMatchIterator.java
@@ -0,0 +1,107 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.runtime.operators.sort;
+
+import org.apache.flink.api.common.functions.FlatJoinFunction;
+import org.apache.flink.api.common.typeutils.TypeComparator;
+import org.apache.flink.api.common.typeutils.TypePairComparator;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.runtime.io.disk.iomanager.IOManager;
+import org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable;
+import org.apache.flink.runtime.memorymanager.MemoryAllocationException;
+import org.apache.flink.runtime.memorymanager.MemoryManager;
+import org.apache.flink.util.Collector;
+import org.apache.flink.util.MutableObjectIterator;
+
+import java.util.Iterator;
+
+/**
+ * An implementation of the {@link org.apache.flink.runtime.operators.util.JoinTaskIterator} that realizes the
+ * matching through a sort-merge join strategy.
+ */
+public abstract class AbstractMergeMatchIterator<T1, T2, O> extends AbstractMergeIterator<T1, T2, O> {
+
+	public AbstractMergeMatchIterator(MutableObjectIterator<T1> input1, MutableObjectIterator<T2> input2,
+									TypeSerializer<T1> serializer1, TypeComparator<T1> comparator1,
+									TypeSerializer<T2> serializer2, TypeComparator<T2> comparator2,
+									TypePairComparator<T1, T2> pairComparator,
+									MemoryManager memoryManager,
+									IOManager ioManager,
+									int numMemoryPages,
+									AbstractInvokable parentTask)
+			throws MemoryAllocationException {
+		super(input1, input2, serializer1, comparator1, serializer2, comparator2, pairComparator, memoryManager, ioManager, numMemoryPages, parentTask);
+	}
+
+	/**
+	 * Calls the <code>JoinFunction#match()</code> method for all two key-value pairs that share the same key and come
+	 * from different inputs. The output of the <code>match()</code> method is forwarded.
+	 * <p>
+	 * This method first zig-zags between the two sorted inputs in order to find a common
+	 * key, and then calls the match stub with the cross product of the values.
+	 *
+	 * @throws Exception Forwards all exceptions from the user code and the I/O system.
+	 * @see org.apache.flink.runtime.operators.util.JoinTaskIterator#callWithNextKey(org.apache.flink.api.common.functions.FlatJoinFunction, org.apache.flink.util.Collector)
+	 */
+	@Override
+	public boolean callWithNextKey(final FlatJoinFunction<T1, T2, O> matchFunction, final Collector<O> collector)
+			throws Exception {
+		if (!this.iterator1.nextKey() || !this.iterator2.nextKey()) {
+			// consume all remaining keys (hack to prevent remaining inputs during iterations, lets get rid of this soon)
+			while (this.iterator1.nextKey()) ;
+			while (this.iterator2.nextKey()) ;
+
+			return false;
+		}
+
+		final TypePairComparator<T1, T2> comparator = this.pairComparator;
+		comparator.setReference(this.iterator1.getCurrent());
+		T2 current2 = this.iterator2.getCurrent();
+
+		// zig zag
+		while (true) {
+			// determine the relation between the (possibly composite) keys
+			final int comp = comparator.compareToReference(current2);
+
+			if (comp == 0) {
+				break;
+			}
+
+			if (comp < 0) {
+				if (!this.iterator2.nextKey()) {
+					return false;
+				}
+				current2 = this.iterator2.getCurrent();
+			} else {
+				if (!this.iterator1.nextKey()) {
+					return false;
+				}
+				comparator.setReference(this.iterator1.getCurrent());
+			}
+		}
+
+		// here, we have a common key! call the match function with the cross product of the
+		// values
+		final Iterator<T1> values1 = this.iterator1.getValues();
+		final Iterator<T2> values2 = this.iterator2.getValues();
+
+		crossMatchingGroup(values1, values2, matchFunction, collector);
+		return true;
+	}
+}

http://git-wip-us.apache.org/repos/asf/flink/blob/0dc6849a/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/NonReusingMergeMatchIterator.java
----------------------------------------------------------------------
diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/NonReusingMergeMatchIterator.java b/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/NonReusingMergeMatchIterator.java
index c89b5c5..9705778 100644
--- a/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/NonReusingMergeMatchIterator.java
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/NonReusingMergeMatchIterator.java
@@ -7,7 +7,7 @@
  * "License"); you may not use this file except in compliance
  * with the License.  You may obtain a copy of the License at
  *
- * http://www.apache.org/licenses/LICENSE-2.0
+ *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
@@ -18,60 +18,19 @@
 
 package org.apache.flink.runtime.operators.sort;
 
-import org.apache.flink.api.common.functions.FlatJoinFunction;
 import org.apache.flink.api.common.typeutils.TypeComparator;
 import org.apache.flink.api.common.typeutils.TypePairComparator;
 import org.apache.flink.api.common.typeutils.TypeSerializer;
-import org.apache.flink.core.memory.MemorySegment;
 import org.apache.flink.runtime.io.disk.iomanager.IOManager;
 import org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable;
 import org.apache.flink.runtime.memorymanager.MemoryAllocationException;
 import org.apache.flink.runtime.memorymanager.MemoryManager;
-import org.apache.flink.runtime.operators.resettable.NonReusingBlockResettableIterator;
-import org.apache.flink.runtime.operators.resettable.SpillingResettableIterator;
-import org.apache.flink.runtime.operators.util.JoinTaskIterator;
+import org.apache.flink.runtime.util.KeyGroupedIterator;
 import org.apache.flink.runtime.util.NonReusingKeyGroupedIterator;
-import org.apache.flink.util.Collector;
 import org.apache.flink.util.MutableObjectIterator;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
-import java.io.IOException;
-import java.util.Iterator;
-import java.util.List;
 
-/**
- * An implementation of the {@link org.apache.flink.runtime.operators.util.JoinTaskIterator} that realizes the
- * matching through a sort-merge join strategy.
- */
-public class NonReusingMergeMatchIterator<T1, T2, O> implements JoinTaskIterator<T1, T2, O> {
-
-	/**
-	 * The log used by this iterator to log messages.
-	 */
-	private static final Logger LOG = LoggerFactory.getLogger(NonReusingMergeMatchIterator.class);
-
-	// --------------------------------------------------------------------------------------------
-
-	private TypePairComparator<T1, T2> comp;
-
-	private NonReusingKeyGroupedIterator<T1> iterator1;
-
-	private NonReusingKeyGroupedIterator<T2> iterator2;
-
-	private final TypeSerializer<T1> serializer1;
-
-	private final TypeSerializer<T2> serializer2;
-
-	private final NonReusingBlockResettableIterator<T2> blockIt;	// for N:M cross products with same key
-
-	private final List<MemorySegment> memoryForSpillingIterator;
-
-	private final MemoryManager memoryManager;
-
-	private final IOManager ioManager;
-
-	// --------------------------------------------------------------------------------------------
+public class NonReusingMergeMatchIterator<T1, T2, O> extends AbstractMergeMatchIterator<T1, T2, O> {
 
 	public NonReusingMergeMatchIterator(
 			MutableObjectIterator<T1> input1,
@@ -83,341 +42,18 @@ public class NonReusingMergeMatchIterator<T1, T2, O> implements JoinTaskIterator
 			IOManager ioManager,
 			int numMemoryPages,
 			AbstractInvokable parentTask)
-	throws MemoryAllocationException
-	{
-		if (numMemoryPages < 2) {
-			throw new IllegalArgumentException("Merger needs at least 2 memory pages.");
-		}
-
-		this.comp = pairComparator;
-		this.serializer1 = serializer1;
-		this.serializer2 = serializer2;
-
-		this.memoryManager = memoryManager;
-		this.ioManager = ioManager;
-
-		this.iterator1 = new NonReusingKeyGroupedIterator<T1>(input1, comparator1.duplicate());
-		this.iterator2 = new NonReusingKeyGroupedIterator<T2>(input2, comparator2.duplicate());
-
-		final int numPagesForSpiller = numMemoryPages > 20 ? 2 : 1;
-		this.blockIt = new NonReusingBlockResettableIterator<T2>(this.memoryManager, this.serializer2,
-			(numMemoryPages - numPagesForSpiller), parentTask);
-		this.memoryForSpillingIterator = memoryManager.allocatePages(parentTask, numPagesForSpiller);
+			throws MemoryAllocationException {
+		super(input1, input2, serializer1, comparator1, serializer2, comparator2, pairComparator, memoryManager, ioManager, numMemoryPages, parentTask);
 	}
 
-
-	@Override
-	public void open() throws IOException {}
-
-
-	@Override
-	public void close() {
-		if (this.blockIt != null) {
-			try {
-				this.blockIt.close();
-			}
-			catch (Throwable t) {
-				LOG.error("Error closing block memory iterator: " + t.getMessage(), t);
-			}
-		}
-
-		this.memoryManager.release(this.memoryForSpillingIterator);
-	}
-
-
 	@Override
-	public void abort() {
-		close();
+	protected <T> KeyGroupedIterator<T> createKeyGroupedIterator(MutableObjectIterator<T> input, TypeSerializer<T> serializer, TypeComparator<T> comparator) {
+		return new NonReusingKeyGroupedIterator<T>(input, comparator);
 	}
 
-	/**
-	 * Calls the <code>JoinFunction#match()</code> method for all two key-value pairs that share the same key and come
-	 * from different inputs. The output of the <code>match()</code> method is forwarded.
-	 * <p>
-	 * This method first zig-zags between the two sorted inputs in order to find a common
-	 * key, and then calls the match stub with the cross product of the values.
-	 *
-	 * @throws Exception Forwards all exceptions from the user code and the I/O system.
-	 *
-	 * @see org.apache.flink.runtime.operators.util.JoinTaskIterator#callWithNextKey(org.apache.flink.api.common.functions.FlatJoinFunction, org.apache.flink.util.Collector)
-	 */
 	@Override
-	public boolean callWithNextKey(final FlatJoinFunction<T1, T2, O> matchFunction, final Collector<O> collector)
-	throws Exception
-	{
-		if (!this.iterator1.nextKey() || !this.iterator2.nextKey()) {
-			// consume all remaining keys (hack to prevent remaining inputs during iterations, lets get rid of this soon)
-			while (this.iterator1.nextKey());
-			while (this.iterator2.nextKey());
-			
-			return false;
-		}
-
-		final TypePairComparator<T1, T2> comparator = this.comp;
-		comparator.setReference(this.iterator1.getCurrent());
-		T2 current2 = this.iterator2.getCurrent();
-				
-		// zig zag
-		while (true) {
-			// determine the relation between the (possibly composite) keys
-			final int comp = comparator.compareToReference(current2);
-			
-			if (comp == 0) {
-				break;
-			}
-			
-			if (comp < 0) {
-				if (!this.iterator2.nextKey()) {
-					return false;
-				}
-				current2 = this.iterator2.getCurrent();
-			}
-			else {
-				if (!this.iterator1.nextKey()) {
-					return false;
-				}
-				comparator.setReference(this.iterator1.getCurrent());
-			}
-		}
-		
-		// here, we have a common key! call the match function with the cross product of the
-		// values
-		final NonReusingKeyGroupedIterator<T1>.ValuesIterator values1 = this.iterator1.getValues();
-		final NonReusingKeyGroupedIterator<T2>.ValuesIterator values2 = this.iterator2.getValues();
-		
-		final T1 firstV1 = values1.next();
-		final T2 firstV2 = values2.next();	
-			
-		final boolean v1HasNext = values1.hasNext();
-		final boolean v2HasNext = values2.hasNext();
-
-		// check if one side is already empty
-		// this check could be omitted if we put this in MatchTask.
-		// then we can derive the local strategy (with build side).
-		
-		if (v1HasNext) {
-			if (v2HasNext) {
-				// both sides contain more than one value
-				// TODO: Decide which side to spill and which to block!
-				crossMwithNValues(firstV1, values1, firstV2, values2, matchFunction, collector);
-			} else {
-				crossSecond1withNValues(firstV2, firstV1, values1, matchFunction, collector);
-			}
-		} else {
-			if (v2HasNext) {
-				crossFirst1withNValues(firstV1, firstV2, values2, matchFunction, collector);
-			} else {
-				// both sides contain only one value
-				matchFunction.join(firstV1, firstV2, collector);
-			}
-		}
-		return true;
-	}
-
-	/**
-	 * Crosses a single value from the first input with N values, all sharing a common key.
-	 * Effectively realizes a <i>1:N</i> match (join).
-	 * 
-	 * @param val1 The value form the <i>1</i> side.
-	 * @param firstValN The first of the values from the <i>N</i> side.
-	 * @param valsN Iterator over remaining <i>N</i> side values.
-	 *          
-	 * @throws Exception Forwards all exceptions thrown by the stub.
-	 */
-	private void crossFirst1withNValues(final T1 val1, final T2 firstValN,
-			final Iterator<T2> valsN, final FlatJoinFunction<T1, T2, O> matchFunction, final Collector<O> collector)
-	throws Exception
-	{
-		T1 copy1 = this.serializer1.copy(val1);
-		matchFunction.join(copy1, firstValN, collector);
-		
-		// set copy and match first element
-		boolean more = true;
-		do {
-			final T2 nRec = valsN.next();
-			
-			if (valsN.hasNext()) {
-				copy1 = this.serializer1.copy(val1);
-				matchFunction.join(copy1, nRec, collector);
-			} else {
-				matchFunction.join(val1, nRec, collector);
-				more = false;
-			}
-		}
-		while (more);
-	}
-	
-	/**
-	 * Crosses a single value from the second side with N values, all sharing a common key.
-	 * Effectively realizes a <i>N:1</i> match (join).
-	 * 
-	 * @param val1 The value form the <i>1</i> side.
-	 * @param firstValN The first of the values from the <i>N</i> side.
-	 * @param valsN Iterator over remaining <i>N</i> side values.
-	 *          
-	 * @throws Exception Forwards all exceptions thrown by the stub.
-	 */
-	private void crossSecond1withNValues(T2 val1, T1 firstValN,
-			Iterator<T1> valsN, FlatJoinFunction<T1, T2, O> matchFunction, Collector<O> collector)
-	throws Exception
-	{
-		T2 copy2 = this.serializer2.copy(val1);
-		matchFunction.join(firstValN, copy2, collector);
-		
-		// set copy and match first element
-		boolean more = true;
-		do {
-			final T1 nRec = valsN.next();
-			
-			if (valsN.hasNext()) {
-				copy2 = this.serializer2.copy(val1);
-				matchFunction.join(nRec, copy2, collector);
-			} else {
-				matchFunction.join(nRec, val1, collector);
-				more = false;
-			}
-		}
-		while (more);
+	protected <T> T createCopy(TypeSerializer<T> serializer, T value, T reuse) {
+		return serializer.copy(value);
 	}
-	
-	/**
-	 * @param firstV1
-	 * @param spillVals
-	 * @param firstV2
-	 * @param blockVals
-	 */
-	private void crossMwithNValues(final T1 firstV1, Iterator<T1> spillVals,
-			final T2 firstV2, final Iterator<T2> blockVals,
-			final FlatJoinFunction<T1, T2, O> matchFunction, final Collector<O> collector)
-	throws Exception
-	{
-		// ==================================================
-		// We have one first (head) element from both inputs (firstV1 and firstV2)
-		// We have an iterator for both inputs.
-		// we make the V1 side the spilling side and the V2 side the blocking side.
-		// In order to get the full cross product without unnecessary spilling, we do the
-		// following:
-		// 1) cross the heads
-		// 2) cross the head of the spilling side against the first block of the blocking side
-		// 3) cross the iterator of the spilling side with the head of the block side
-		// 4) cross the iterator of the spilling side with the first block
-		// ---------------------------------------------------
-		// If the blocking side has more than one block, we really need to make the spilling side fully
-		// resettable. For each further block on the block side, we do:
-		// 5) cross the head of the spilling side with the next block
-		// 6) cross the spilling iterator with the next block.
-		
-		// match the first values first
-		T1 copy1 = this.serializer1.copy(firstV1);
-		T2 blockHeadCopy = this.serializer2.copy(firstV2);
-		T1 spillHeadCopy = null;
 
-
-		// --------------- 1) Cross the heads -------------------
-		matchFunction.join(copy1, firstV2, collector);
-		
-		// for the remaining values, we do a block-nested-loops join
-		SpillingResettableIterator<T1> spillIt = null;
-		
-		try {
-			// create block iterator on the second input
-			this.blockIt.reopen(blockVals);
-			
-			// ------------- 2) cross the head of the spilling side with the first block ------------------
-			while (this.blockIt.hasNext()) {
-				final T2 nextBlockRec = this.blockIt.next();
-				copy1 = this.serializer1.copy(firstV1);
-				matchFunction.join(copy1, nextBlockRec, collector);
-			}
-			this.blockIt.reset();
-			
-			// spilling is required if the blocked input has data beyond the current block.
-			// in that case, create the spilling iterator
-			final Iterator<T1> leftSideIter;
-			final boolean spillingRequired = this.blockIt.hasFurtherInput();
-			if (spillingRequired)
-			{
-				// more data than would fit into one block. we need to wrap the other side in a spilling iterator
-				// create spilling iterator on first input
-				spillIt = new SpillingResettableIterator<T1>(spillVals, this.serializer1,
-						this.memoryManager, this.ioManager, this.memoryForSpillingIterator);
-				leftSideIter = spillIt;
-				spillIt.open();
-				
-				spillHeadCopy = this.serializer1.copy(firstV1);
-			}
-			else {
-				leftSideIter = spillVals;
-			}
-			
-			// cross the values in the v1 iterator against the current block
-			
-			while (leftSideIter.hasNext()) {
-				final T1 nextSpillVal = leftSideIter.next();
-				copy1 = this.serializer1.copy(nextSpillVal);
-				
-				
-				// -------- 3) cross the iterator of the spilling side with the head of the block side --------
-				T2 copy2 = this.serializer2.copy(blockHeadCopy);
-				matchFunction.join(copy1, copy2, collector);
-				
-				// -------- 4) cross the iterator of the spilling side with the first block --------
-				while (this.blockIt.hasNext()) {
-					T2 nextBlockRec = this.blockIt.next();
-					
-					// get instances of key and block value
-					copy1 = this.serializer1.copy(nextSpillVal);
-					matchFunction.join(copy1, nextBlockRec, collector);
-				}
-				// reset block iterator
-				this.blockIt.reset();
-			}
-			
-			// if everything from the block-side fit into a single block, we are done.
-			// note that in this special case, we did not create a spilling iterator at all
-			if (!spillingRequired) {
-				return;
-			}
-			
-			// here we are, because we have more blocks on the block side
-			// loop as long as there are blocks from the blocked input
-			while (this.blockIt.nextBlock())
-			{
-				// rewind the spilling iterator
-				spillIt.reset();
-				
-				// ------------- 5) cross the head of the spilling side with the next block ------------
-				while (this.blockIt.hasNext()) {
-					copy1 = this.serializer1.copy(spillHeadCopy);
-					final T2 nextBlockVal = blockIt.next();
-					matchFunction.join(copy1, nextBlockVal, collector);
-				}
-				this.blockIt.reset();
-				
-				// -------- 6) cross the spilling iterator with the next block. ------------------
-				while (spillIt.hasNext())
-				{
-					// get value from resettable iterator
-					final T1 nextSpillVal = spillIt.next();
-					// cross value with block values
-					while (this.blockIt.hasNext()) {
-						// get instances of key and block value
-						final T2 nextBlockVal = this.blockIt.next();
-						copy1 = this.serializer1.copy(nextSpillVal);
-						matchFunction.join(copy1, nextBlockVal, collector);
-					}
-					
-					// reset block iterator
-					this.blockIt.reset();
-				}
-				// reset v1 iterator
-				spillIt.reset();
-			}
-		}
-		finally {
-			if (spillIt != null) {
-				this.memoryForSpillingIterator.addAll(spillIt.close());
-			}
-		}
-	}
 }

http://git-wip-us.apache.org/repos/asf/flink/blob/0dc6849a/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/ReusingMergeMatchIterator.java
----------------------------------------------------------------------
diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/ReusingMergeMatchIterator.java b/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/ReusingMergeMatchIterator.java
index 66beee1..c9cf5a2 100644
--- a/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/ReusingMergeMatchIterator.java
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/operators/sort/ReusingMergeMatchIterator.java
@@ -18,70 +18,20 @@
 
 package org.apache.flink.runtime.operators.sort;
 
-import java.io.IOException;
-import java.util.Iterator;
-import java.util.List;
-
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-import org.apache.flink.api.common.functions.FlatJoinFunction;
 import org.apache.flink.api.common.typeutils.TypeComparator;
 import org.apache.flink.api.common.typeutils.TypePairComparator;
 import org.apache.flink.api.common.typeutils.TypeSerializer;
-import org.apache.flink.core.memory.MemorySegment;
 import org.apache.flink.runtime.io.disk.iomanager.IOManager;
 import org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable;
 import org.apache.flink.runtime.memorymanager.MemoryAllocationException;
 import org.apache.flink.runtime.memorymanager.MemoryManager;
-import org.apache.flink.runtime.operators.resettable.NonReusingBlockResettableIterator;
-import org.apache.flink.runtime.operators.resettable.SpillingResettableIterator;
-import org.apache.flink.runtime.operators.util.JoinTaskIterator;
+import org.apache.flink.runtime.util.KeyGroupedIterator;
 import org.apache.flink.runtime.util.ReusingKeyGroupedIterator;
-import org.apache.flink.util.Collector;
 import org.apache.flink.util.MutableObjectIterator;
 
 
-/**
- * An implementation of the {@link JoinTaskIterator} that realizes the
- * matching through a sort-merge join strategy.
- */
-public class ReusingMergeMatchIterator<T1, T2, O> implements JoinTaskIterator<T1, T2, O> {
-	
-	/**
-	 * The log used by this iterator to log messages.
-	 */
-	private static final Logger LOG = LoggerFactory.getLogger(ReusingMergeMatchIterator.class);
-	
-	// --------------------------------------------------------------------------------------------
-	
-	private TypePairComparator<T1, T2> comp;
-	
-	private ReusingKeyGroupedIterator<T1> iterator1;
-
-	private ReusingKeyGroupedIterator<T2> iterator2;
-	
-	private final TypeSerializer<T1> serializer1;
-	
-	private final TypeSerializer<T2> serializer2;
-	
-	private T1 copy1;
-	
-	private T1 spillHeadCopy;
-	
-	private T2 copy2;
-	
-	private T2 blockHeadCopy;
-	
-	private final NonReusingBlockResettableIterator<T2> blockIt;				// for N:M cross products with same key
-	
-	private final List<MemorySegment> memoryForSpillingIterator;
-	
-	private final MemoryManager memoryManager;
+public class ReusingMergeMatchIterator<T1, T2, O> extends AbstractMergeMatchIterator<T1, T2, O> {
 
-	private final IOManager ioManager;
-	
-	// --------------------------------------------------------------------------------------------
-	
 	public ReusingMergeMatchIterator(
 			MutableObjectIterator<T1> input1,
 			MutableObjectIterator<T2> input2,
@@ -92,344 +42,23 @@ public class ReusingMergeMatchIterator<T1, T2, O> implements JoinTaskIterator<T1
 			IOManager ioManager,
 			int numMemoryPages,
 			AbstractInvokable parentTask)
-	throws MemoryAllocationException
-	{
-		if (numMemoryPages < 2) {
-			throw new IllegalArgumentException("Merger needs at least 2 memory pages.");
-		}
-		
-		this.comp = pairComparator;
-		this.serializer1 = serializer1;
-		this.serializer2 = serializer2;
-		
+			throws MemoryAllocationException {
+		super(input1, input2, serializer1, comparator1, serializer2, comparator2, pairComparator, memoryManager, ioManager, numMemoryPages, parentTask);
+
 		this.copy1 = serializer1.createInstance();
 		this.spillHeadCopy = serializer1.createInstance();
 		this.copy2 = serializer2.createInstance();
 		this.blockHeadCopy = serializer2.createInstance();
-		
-		this.memoryManager = memoryManager;
-		this.ioManager = ioManager;
-		
-		this.iterator1 = new ReusingKeyGroupedIterator<T1>(input1, this.serializer1, comparator1.duplicate());
-		this.iterator2 = new ReusingKeyGroupedIterator<T2>(input2, this.serializer2, comparator2.duplicate());
-		
-		final int numPagesForSpiller = numMemoryPages > 20 ? 2 : 1;
-		this.blockIt = new NonReusingBlockResettableIterator<T2>(this.memoryManager, this.serializer2,
-			(numMemoryPages - numPagesForSpiller), parentTask);
-		this.memoryForSpillingIterator = memoryManager.allocatePages(parentTask, numPagesForSpiller);
-	}
-
-
-	@Override
-	public void open() throws IOException {}
-
-
-	@Override
-	public void close() {
-		if (this.blockIt != null) {
-			try {
-				this.blockIt.close();
-			}
-			catch (Throwable t) {
-				LOG.error("Error closing block memory iterator: " + t.getMessage(), t);
-			}
-		}
-		
-		this.memoryManager.release(this.memoryForSpillingIterator);
 	}
-	
 
 	@Override
-	public void abort() {
-		close();
+	protected <T> KeyGroupedIterator<T> createKeyGroupedIterator(MutableObjectIterator<T> input, TypeSerializer<T> serializer, TypeComparator<T> comparator) {
+		return new ReusingKeyGroupedIterator<T>(input, serializer, comparator);
 	}
 
-	/**
-	 * Calls the <code>JoinFunction#match()</code> method for all two key-value pairs that share the same key and come 
-	 * from different inputs. The output of the <code>match()</code> method is forwarded.
-	 * <p>
-	 * This method first zig-zags between the two sorted inputs in order to find a common
-	 * key, and then calls the match stub with the cross product of the values.
-	 * 
-	 * @throws Exception Forwards all exceptions from the user code and the I/O system.
-	 * 
-	 * @see org.apache.flink.runtime.operators.util.JoinTaskIterator#callWithNextKey(FlatJoinFunction, Collector)
-	 */
 	@Override
-	public boolean callWithNextKey(final FlatJoinFunction<T1, T2, O> matchFunction, final Collector<O> collector)
-	throws Exception
-	{
-		if (!this.iterator1.nextKey() || !this.iterator2.nextKey()) {
-			// consume all remaining keys (hack to prevent remaining inputs during iterations, lets get rid of this soon)
-			while (this.iterator1.nextKey());
-			while (this.iterator2.nextKey());
-			
-			return false;
-		}
-
-		final TypePairComparator<T1, T2> comparator = this.comp;
-		comparator.setReference(this.iterator1.getCurrent());
-		T2 current2 = this.iterator2.getCurrent();
-				
-		// zig zag
-		while (true) {
-			// determine the relation between the (possibly composite) keys
-			final int comp = comparator.compareToReference(current2);
-			
-			if (comp == 0) {
-				break;
-			}
-			
-			if (comp < 0) {
-				if (!this.iterator2.nextKey()) {
-					return false;
-				}
-				current2 = this.iterator2.getCurrent();
-			}
-			else {
-				if (!this.iterator1.nextKey()) {
-					return false;
-				}
-				comparator.setReference(this.iterator1.getCurrent());
-			}
-		}
-		
-		// here, we have a common key! call the match function with the cross product of the
-		// values
-		final ReusingKeyGroupedIterator<T1>.ValuesIterator values1 = this.iterator1.getValues();
-		final ReusingKeyGroupedIterator<T2>.ValuesIterator values2 = this.iterator2.getValues();
-		
-		final T1 firstV1 = values1.next();
-		final T2 firstV2 = values2.next();	
-			
-		final boolean v1HasNext = values1.hasNext();
-		final boolean v2HasNext = values2.hasNext();
-
-		// check if one side is already empty
-		// this check could be omitted if we put this in MatchTask.
-		// then we can derive the local strategy (with build side).
-		
-		if (v1HasNext) {
-			if (v2HasNext) {
-				// both sides contain more than one value
-				// TODO: Decide which side to spill and which to block!
-				crossMwithNValues(firstV1, values1, firstV2, values2, matchFunction, collector);
-			} else {
-				crossSecond1withNValues(firstV2, firstV1, values1, matchFunction, collector);
-			}
-		} else {
-			if (v2HasNext) {
-				crossFirst1withNValues(firstV1, firstV2, values2, matchFunction, collector);
-			} else {
-				// both sides contain only one value
-				matchFunction.join(firstV1, firstV2, collector);
-			}
-		}
-		return true;
+	protected <T> T createCopy(TypeSerializer<T> serializer, T value, T reuse) {
+		return serializer.copy(value, reuse);
 	}
 
-	/**
-	 * Crosses a single value from the first input with N values, all sharing a common key.
-	 * Effectively realizes a <i>1:N</i> match (join).
-	 * 
-	 * @param val1 The value form the <i>1</i> side.
-	 * @param firstValN The first of the values from the <i>N</i> side.
-	 * @param valsN Iterator over remaining <i>N</i> side values.
-	 *          
-	 * @throws Exception Forwards all exceptions thrown by the stub.
-	 */
-	private void crossFirst1withNValues(final T1 val1, final T2 firstValN,
-			final Iterator<T2> valsN, final FlatJoinFunction<T1, T2, O> matchFunction, final Collector<O> collector)
-	throws Exception
-	{
-		this.copy1 = this.serializer1.copy(val1, this.copy1);
-		matchFunction.join(this.copy1, firstValN, collector);
-		
-		// set copy and match first element
-		boolean more = true;
-		do {
-			final T2 nRec = valsN.next();
-			
-			if (valsN.hasNext()) {
-				this.copy1 = this.serializer1.copy(val1, this.copy1);
-				matchFunction.join(this.copy1, nRec, collector);
-			} else {
-				matchFunction.join(val1, nRec, collector);
-				more = false;
-			}
-		}
-		while (more);
-	}
-	
-	/**
-	 * Crosses a single value from the second side with N values, all sharing a common key.
-	 * Effectively realizes a <i>N:1</i> match (join).
-	 * 
-	 * @param val1 The value form the <i>1</i> side.
-	 * @param firstValN The first of the values from the <i>N</i> side.
-	 * @param valsN Iterator over remaining <i>N</i> side values.
-	 *          
-	 * @throws Exception Forwards all exceptions thrown by the stub.
-	 */
-	private void crossSecond1withNValues(T2 val1, T1 firstValN,
-			Iterator<T1> valsN, FlatJoinFunction<T1, T2, O> matchFunction, Collector<O> collector)
-	throws Exception
-	{
-		this.copy2 = this.serializer2.copy(val1, this.copy2);
-		matchFunction.join(firstValN, this.copy2, collector);
-		
-		// set copy and match first element
-		boolean more = true;
-		do {
-			final T1 nRec = valsN.next();
-			
-			if (valsN.hasNext()) {
-				this.copy2 = this.serializer2.copy(val1, this.copy2);
-				matchFunction.join(nRec,this.copy2,collector);
-			} else {
-				matchFunction.join(nRec, val1, collector);
-				more = false;
-			}
-		}
-		while (more);
-	}
-	
-	/**
-	 * @param firstV1
-	 * @param spillVals
-	 * @param firstV2
-	 * @param blockVals
-	 */
-	private void crossMwithNValues(final T1 firstV1, Iterator<T1> spillVals,
-			final T2 firstV2, final Iterator<T2> blockVals,
-			final FlatJoinFunction<T1, T2, O> matchFunction, final Collector<O> collector)
-	throws Exception
-	{
-		// ==================================================
-		// We have one first (head) element from both inputs (firstV1 and firstV2)
-		// We have an iterator for both inputs.
-		// we make the V1 side the spilling side and the V2 side the blocking side.
-		// In order to get the full cross product without unnecessary spilling, we do the
-		// following:
-		// 1) cross the heads
-		// 2) cross the head of the spilling side against the first block of the blocking side
-		// 3) cross the iterator of the spilling side with the head of the block side
-		// 4) cross the iterator of the spilling side with the first block
-		// ---------------------------------------------------
-		// If the blocking side has more than one block, we really need to make the spilling side fully
-		// resettable. For each further block on the block side, we do:
-		// 5) cross the head of the spilling side with the next block
-		// 6) cross the spilling iterator with the next block.
-		
-		// match the first values first
-		this.copy1 = this.serializer1.copy(firstV1, this.copy1);
-		this.blockHeadCopy = this.serializer2.copy(firstV2, this.blockHeadCopy);
-		
-		// --------------- 1) Cross the heads -------------------
-		matchFunction.join(this.copy1, firstV2, collector);
-		
-		// for the remaining values, we do a block-nested-loops join
-		SpillingResettableIterator<T1> spillIt = null;
-		
-		try {
-			// create block iterator on the second input
-			this.blockIt.reopen(blockVals);
-			
-			// ------------- 2) cross the head of the spilling side with the first block ------------------
-			while (this.blockIt.hasNext()) {
-				final T2 nextBlockRec = this.blockIt.next();
-				this.copy1 = this.serializer1.copy(firstV1, this.copy1);
-				matchFunction.join(this.copy1, nextBlockRec, collector);
-			}
-			this.blockIt.reset();
-			
-			// spilling is required if the blocked input has data beyond the current block.
-			// in that case, create the spilling iterator
-			final Iterator<T1> leftSideIter;
-			final boolean spillingRequired = this.blockIt.hasFurtherInput();
-			if (spillingRequired)
-			{
-				// more data than would fit into one block. we need to wrap the other side in a spilling iterator
-				// create spilling iterator on first input
-				spillIt = new SpillingResettableIterator<T1>(spillVals, this.serializer1,
-						this.memoryManager, this.ioManager, this.memoryForSpillingIterator);
-				leftSideIter = spillIt;
-				spillIt.open();
-				
-				this.spillHeadCopy = this.serializer1.copy(firstV1, this.spillHeadCopy);
-			}
-			else {
-				leftSideIter = spillVals;
-			}
-			
-			// cross the values in the v1 iterator against the current block
-			
-			while (leftSideIter.hasNext()) {
-				final T1 nextSpillVal = leftSideIter.next();
-				this.copy1 = this.serializer1.copy(nextSpillVal, this.copy1);
-				
-				
-				// -------- 3) cross the iterator of the spilling side with the head of the block side --------
-				this.copy2 = this.serializer2.copy(this.blockHeadCopy, this.copy2);
-				matchFunction.join(this.copy1, this.copy2, collector);
-				
-				// -------- 4) cross the iterator of the spilling side with the first block --------
-				while (this.blockIt.hasNext()) {
-					T2 nextBlockRec = this.blockIt.next();
-					
-					// get instances of key and block value
-					this.copy1 = this.serializer1.copy(nextSpillVal, this.copy1);
-					matchFunction.join(this.copy1, nextBlockRec, collector);
-				}
-				// reset block iterator
-				this.blockIt.reset();
-			}
-			
-			// if everything from the block-side fit into a single block, we are done.
-			// note that in this special case, we did not create a spilling iterator at all
-			if (!spillingRequired) {
-				return;
-			}
-			
-			// here we are, because we have more blocks on the block side
-			// loop as long as there are blocks from the blocked input
-			while (this.blockIt.nextBlock())
-			{
-				// rewind the spilling iterator
-				spillIt.reset();
-				
-				// ------------- 5) cross the head of the spilling side with the next block ------------
-				while (this.blockIt.hasNext()) {
-					this.copy1 = this.serializer1.copy(this.spillHeadCopy, this.copy1);
-					final T2 nextBlockVal = blockIt.next();
-					matchFunction.join(this.copy1, nextBlockVal, collector);
-				}
-				this.blockIt.reset();
-				
-				// -------- 6) cross the spilling iterator with the next block. ------------------
-				while (spillIt.hasNext())
-				{
-					// get value from resettable iterator
-					final T1 nextSpillVal = spillIt.next();
-					// cross value with block values
-					while (this.blockIt.hasNext()) {
-						// get instances of key and block value
-						final T2 nextBlockVal = this.blockIt.next();
-						this.copy1 = this.serializer1.copy(nextSpillVal, this.copy1);
-						matchFunction.join(this.copy1, nextBlockVal, collector);
-					}
-					
-					// reset block iterator
-					this.blockIt.reset();
-				}
-				// reset v1 iterator
-				spillIt.reset();
-			}
-		}
-		finally {
-			if (spillIt != null) {
-				this.memoryForSpillingIterator.addAll(spillIt.close());
-			}
-		}
-	}
 }

http://git-wip-us.apache.org/repos/asf/flink/blob/0dc6849a/flink-runtime/src/main/java/org/apache/flink/runtime/util/KeyGroupedIterator.java
----------------------------------------------------------------------
diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/util/KeyGroupedIterator.java b/flink-runtime/src/main/java/org/apache/flink/runtime/util/KeyGroupedIterator.java
new file mode 100644
index 0000000..64e8298
--- /dev/null
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/util/KeyGroupedIterator.java
@@ -0,0 +1,31 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.runtime.util;
+
+import java.io.IOException;
+import java.util.Iterator;
+
+public interface KeyGroupedIterator<E> {
+
+	boolean nextKey() throws IOException;
+
+	E getCurrent();
+
+	Iterator<E> getValues();
+}

http://git-wip-us.apache.org/repos/asf/flink/blob/0dc6849a/flink-runtime/src/main/java/org/apache/flink/runtime/util/NonReusingKeyGroupedIterator.java
----------------------------------------------------------------------
diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/util/NonReusingKeyGroupedIterator.java b/flink-runtime/src/main/java/org/apache/flink/runtime/util/NonReusingKeyGroupedIterator.java
index 3f28cfc..6f4448c 100644
--- a/flink-runtime/src/main/java/org/apache/flink/runtime/util/NonReusingKeyGroupedIterator.java
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/util/NonReusingKeyGroupedIterator.java
@@ -29,7 +29,7 @@ import org.apache.flink.util.TraversableOnceException;
 /**
  * The key grouped iterator returns a key and all values that share the same key.
  */
-public final class NonReusingKeyGroupedIterator<E> {
+public final class NonReusingKeyGroupedIterator<E> implements KeyGroupedIterator<E> {
 	
 	private final MutableObjectIterator<E> iterator;
 	

http://git-wip-us.apache.org/repos/asf/flink/blob/0dc6849a/flink-runtime/src/main/java/org/apache/flink/runtime/util/ReusingKeyGroupedIterator.java
----------------------------------------------------------------------
diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/util/ReusingKeyGroupedIterator.java b/flink-runtime/src/main/java/org/apache/flink/runtime/util/ReusingKeyGroupedIterator.java
index 4dc9dd3..1477f10 100644
--- a/flink-runtime/src/main/java/org/apache/flink/runtime/util/ReusingKeyGroupedIterator.java
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/util/ReusingKeyGroupedIterator.java
@@ -31,7 +31,7 @@ import org.apache.flink.util.TraversableOnceException;
  * The KeyValueIterator returns a key and all values that belong to the key (share the same key).
  * 
  */
-public final class ReusingKeyGroupedIterator<E> {
+public final class ReusingKeyGroupedIterator<E> implements KeyGroupedIterator<E> {
 	
 	private final MutableObjectIterator<E> iterator;
 
@@ -78,6 +78,7 @@ public final class ReusingKeyGroupedIterator<E> {
 	 * 
 	 * @return true if the input iterator has an other group of key-value pairs that share the same key.
 	 */
+	@Override
 	public boolean nextKey() throws IOException
 	{
 		// first element (or empty)
@@ -139,6 +140,7 @@ public final class ReusingKeyGroupedIterator<E> {
 		return this.comparator;
 	}
 	
+	@Override
 	public E getCurrent() {
 		return this.current;
 	}
@@ -150,6 +152,7 @@ public final class ReusingKeyGroupedIterator<E> {
 	 * 
 	 * @return Iterator over all values that belong to the current key.
 	 */
+	@Override
 	public ValuesIterator getValues() {
 		return this.valuesIterator;
 	}


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