| /* |
| * 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.drill.metastore.statistics; |
| |
| import java.util.List; |
| |
| /** |
| * This class represents kinds of column statistics which may be received as a union |
| * of other statistics, for example column nulls count may be received as a sum of nulls counts |
| * of underlying metadata parts. |
| */ |
| public interface CollectableColumnStatisticsKind<V> extends StatisticsKind<V> { |
| |
| /** |
| * Returns column statistics value received by collecting specified {@link ColumnStatistics}. |
| * |
| * @param statistics list of {@link ColumnStatistics} instances to be collected |
| * @return column statistics value received by collecting specified {@link ColumnStatistics} |
| */ |
| Object mergeStatistics(List<? extends ColumnStatistics<?>> statistics); |
| } |
