| /* |
| * 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.cassandra.db.partitions; |
| |
| import java.util.*; |
| import java.security.MessageDigest; |
| |
| import org.apache.cassandra.db.EmptyIterators; |
| import org.apache.cassandra.db.transform.FilteredPartitions; |
| import org.apache.cassandra.db.transform.MorePartitions; |
| import org.apache.cassandra.db.transform.Transformation; |
| import org.apache.cassandra.utils.AbstractIterator; |
| |
| import org.apache.cassandra.db.SinglePartitionReadCommand; |
| import org.apache.cassandra.db.rows.*; |
| |
| public abstract class PartitionIterators |
| { |
| private PartitionIterators() {} |
| |
| @SuppressWarnings("resource") // The created resources are returned right away |
| public static RowIterator getOnlyElement(final PartitionIterator iter, SinglePartitionReadCommand command) |
| { |
| // If the query has no results, we'll get an empty iterator, but we still |
| // want a RowIterator out of this method, so we return an empty one. |
| RowIterator toReturn = iter.hasNext() |
| ? iter.next() |
| : EmptyIterators.row(command.metadata(), |
| command.partitionKey(), |
| command.clusteringIndexFilter().isReversed()); |
| |
| // Note that in general, we should wrap the result so that it's close method actually |
| // close the whole PartitionIterator. |
| class Close extends Transformation |
| { |
| public void onPartitionClose() |
| { |
| // asserting this only now because it bothers UnfilteredPartitionIterators.Serializer (which might be used |
| // under the provided DataIter) if hasNext() is called before the previously returned iterator hasn't been fully consumed. |
| boolean hadNext = iter.hasNext(); |
| iter.close(); |
| assert !hadNext; |
| } |
| } |
| return Transformation.apply(toReturn, new Close()); |
| } |
| |
| @SuppressWarnings("resource") // The created resources are returned right away |
| public static PartitionIterator concat(final List<PartitionIterator> iterators) |
| { |
| if (iterators.size() == 1) |
| return iterators.get(0); |
| |
| class Extend implements MorePartitions<PartitionIterator> |
| { |
| int i = 0; |
| public PartitionIterator moreContents() |
| { |
| if (i >= iterators.size()) |
| return null; |
| return iterators.get(i++); |
| } |
| } |
| |
| return MorePartitions.extend(EmptyIterators.partition(), new Extend()); |
| } |
| |
| public static PartitionIterator singletonIterator(RowIterator iterator) |
| { |
| return new SingletonPartitionIterator(iterator); |
| } |
| |
| public static void consume(PartitionIterator iterator) |
| { |
| while (iterator.hasNext()) |
| { |
| try (RowIterator partition = iterator.next()) |
| { |
| while (partition.hasNext()) |
| partition.next(); |
| } |
| } |
| } |
| |
| /** |
| * Wraps the provided iterator so it logs the returned rows for debugging purposes. |
| * <p> |
| * Note that this is only meant for debugging as this can log a very large amount of |
| * logging at INFO. |
| */ |
| @SuppressWarnings("resource") // The created resources are returned right away |
| public static PartitionIterator loggingIterator(PartitionIterator iterator, final String id) |
| { |
| class Logger extends Transformation<RowIterator> |
| { |
| public RowIterator applyToPartition(RowIterator partition) |
| { |
| return RowIterators.loggingIterator(partition, id); |
| } |
| } |
| return Transformation.apply(iterator, new Logger()); |
| } |
| |
| private static class SingletonPartitionIterator extends AbstractIterator<RowIterator> implements PartitionIterator |
| { |
| private final RowIterator iterator; |
| private boolean returned; |
| |
| private SingletonPartitionIterator(RowIterator iterator) |
| { |
| this.iterator = iterator; |
| } |
| |
| protected RowIterator computeNext() |
| { |
| if (returned) |
| return endOfData(); |
| |
| returned = true; |
| return iterator; |
| } |
| |
| public void close() |
| { |
| iterator.close(); |
| } |
| } |
| } |