org.apache.flink.runtime.operators.resettable.NonReusingBlockResettableIterator Maven / Gradle / Ivy
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* 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.resettable;
import java.io.IOException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable;
import org.apache.flink.runtime.memory.MemoryAllocationException;
import org.apache.flink.runtime.memory.MemoryManager;
import org.apache.flink.runtime.util.ResettableIterator;
/**
* Implementation of an iterator that fetches a block of data into main memory and offers resettable
* access to the data in that block.
*
*/
public class NonReusingBlockResettableIterator extends AbstractBlockResettableIterator implements ResettableIterator {
public static final Logger LOG = LoggerFactory.getLogger(NonReusingBlockResettableIterator.class);
// ------------------------------------------------------------------------
protected Iterator input;
protected T nextElement;
protected T leftOverElement;
protected boolean readPhase;
protected boolean noMoreBlocks;
// ------------------------------------------------------------------------
public NonReusingBlockResettableIterator(MemoryManager memoryManager, Iterator input,
TypeSerializer serializer, int numPages,
AbstractInvokable ownerTask)
throws MemoryAllocationException
{
this(memoryManager, serializer, numPages, ownerTask);
this.input = input;
}
public NonReusingBlockResettableIterator(MemoryManager memoryManager, TypeSerializer serializer, int numPages, AbstractInvokable ownerTask)
throws MemoryAllocationException
{
super(serializer, memoryManager, numPages, ownerTask);
}
// ------------------------------------------------------------------------
public void reopen(Iterator input) throws IOException {
this.input = input;
this.noMoreBlocks = false;
this.closed = false;
nextBlock();
}
@Override
public boolean hasNext() {
try {
if (this.nextElement == null) {
if (this.readPhase) {
// read phase, get next element from buffer
T tmp = getNextRecord();
if (tmp != null) {
this.nextElement = tmp;
return true;
} else {
return false;
}
} else {
if (this.input.hasNext()) {
final T next = this.input.next();
if (writeNextRecord(next)) {
this.nextElement = next;
return true;
} else {
this.leftOverElement = next;
return false;
}
} else {
this.noMoreBlocks = true;
return false;
}
}
} else {
return true;
}
} catch (IOException ioex) {
throw new RuntimeException("Error (de)serializing record in block resettable iterator.", ioex);
}
}
@Override
public T next() {
if (this.nextElement == null) {
if (!hasNext()) {
throw new NoSuchElementException();
}
}
T out = this.nextElement;
this.nextElement = null;
return out;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
public void reset() {
// a reset always goes to the read phase
this.readPhase = true;
super.reset();
}
@Override
public boolean nextBlock() throws IOException {
// check the state
if (this.closed) {
throw new IllegalStateException("Iterator has been closed.");
}
// check whether more blocks are available
if (this.noMoreBlocks) {
return false;
}
// reset the views in the superclass
super.nextBlock();
T next = this.leftOverElement;
this.leftOverElement = null;
if (next == null) {
if (this.input.hasNext()) {
next = this.input.next();
}
else {
this.noMoreBlocks = true;
return false;
}
}
// write the leftover record
if (!writeNextRecord(next)) {
throw new IOException("BlockResettableIterator could not serialize record into fresh memory block: " +
"Record is too large.");
}
this.nextElement = next;
this.readPhase = false;
return true;
}
/**
* Checks, whether the input that is blocked by this iterator, has further elements
* available. This method may be used to forecast (for example at the point where a
* block is full) whether there will be more data (possibly in another block).
*
* @return True, if there will be more data, false otherwise.
*/
public boolean hasFurtherInput() {
return !this.noMoreBlocks;
}
public void close() {
// suggest that we are in the read phase. because nothing is in the current block,
// read requests will fail
this.readPhase = true;
super.close();
}
}