| /* |
| * 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.aggregation; |
| |
| import java.nio.ByteBuffer; |
| import java.util.Arrays; |
| |
| import org.apache.cassandra.db.Clustering; |
| import org.apache.cassandra.db.ClusteringComparator; |
| import org.apache.cassandra.db.DecoratedKey; |
| import org.apache.cassandra.utils.ByteBufferUtil; |
| |
| /** |
| * A <code>GroupMaker</code> can be used to determine if some sorted rows belongs to the same group or not. |
| */ |
| public abstract class GroupMaker |
| { |
| /** |
| * <code>GroupMaker</code> that groups all the rows together. |
| */ |
| public static final GroupMaker GROUP_EVERYTHING = new GroupMaker() |
| { |
| public boolean isNewGroup(DecoratedKey partitionKey, Clustering clustering) |
| { |
| return false; |
| } |
| |
| public boolean returnAtLeastOneRow() |
| { |
| return true; |
| } |
| }; |
| |
| public static GroupMaker newInstance(ClusteringComparator comparator, int clusteringPrefixSize, GroupingState state) |
| { |
| return new PkPrefixGroupMaker(comparator, clusteringPrefixSize, state); |
| } |
| |
| public static GroupMaker newInstance(ClusteringComparator comparator, int clusteringPrefixSize) |
| { |
| return new PkPrefixGroupMaker(comparator, clusteringPrefixSize); |
| } |
| |
| /** |
| * Checks if a given row belongs to the same group that the previous row or not. |
| * |
| * @param partitionKey the partition key. |
| * @param clustering the row clustering key |
| * @return <code>true</code> if the row belongs to the same group that the previous one, <code>false</code> |
| * otherwise. |
| */ |
| public abstract boolean isNewGroup(DecoratedKey partitionKey, Clustering clustering); |
| |
| /** |
| * Specify if at least one row must be returned. If the selection is performing some aggregations on all the rows, |
| * one row should be returned even if no records were processed. |
| * |
| * @return <code>true</code> if at least one row must be returned, <code>false</code> otherwise. |
| */ |
| public boolean returnAtLeastOneRow() |
| { |
| return false; |
| } |
| |
| private static final class PkPrefixGroupMaker extends GroupMaker |
| { |
| /** |
| * The size of the clustering prefix used to make the groups |
| */ |
| private final int clusteringPrefixSize; |
| |
| /** |
| * The comparator used to compare the clustering prefixes. |
| */ |
| private final ClusteringComparator comparator; |
| |
| /** |
| * The last partition key seen |
| */ |
| private ByteBuffer lastPartitionKey; |
| |
| /** |
| * The last clustering seen |
| */ |
| private Clustering lastClustering; |
| |
| public PkPrefixGroupMaker(ClusteringComparator comparator, int clusteringPrefixSize, GroupingState state) |
| { |
| this(comparator, clusteringPrefixSize); |
| this.lastPartitionKey = state.partitionKey(); |
| this.lastClustering = state.clustering; |
| } |
| |
| public PkPrefixGroupMaker(ClusteringComparator comparator, int clusteringPrefixSize) |
| { |
| this.comparator = comparator; |
| this.clusteringPrefixSize = clusteringPrefixSize; |
| } |
| |
| @Override |
| public boolean isNewGroup(DecoratedKey partitionKey, Clustering clustering) |
| { |
| boolean isNew = false; |
| |
| // We are entering a new group if: |
| // - the partition key is a new one |
| // - the last clustering was not null and does not have the same prefix as the new clustering one |
| if (!partitionKey.getKey().equals(lastPartitionKey)) |
| { |
| lastPartitionKey = partitionKey.getKey(); |
| isNew = true; |
| if (Clustering.STATIC_CLUSTERING == clustering) |
| { |
| lastClustering = null; |
| return true; |
| } |
| } |
| else if (lastClustering != null && comparator.compare(lastClustering, clustering, clusteringPrefixSize) != 0) |
| { |
| isNew = true; |
| } |
| |
| lastClustering = clustering; |
| return isNew; |
| } |
| } |
| } |