| /* |
| * 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.wayang.basic.operators; |
| |
| import org.apache.commons.lang3.Validate; |
| import org.apache.wayang.core.api.Configuration; |
| import org.apache.wayang.core.optimizer.cardinality.CardinalityEstimator; |
| import org.apache.wayang.core.optimizer.cardinality.FixedSizeCardinalityEstimator; |
| import org.apache.wayang.core.plan.wayangplan.UnaryToUnaryOperator; |
| import org.apache.wayang.core.types.DataSetType; |
| |
| import java.util.Optional; |
| |
| |
| /** |
| * This operator returns the count of elements in this stream. |
| */ |
| public class CountOperator<Type> extends UnaryToUnaryOperator<Type, Long> { |
| |
| |
| /** |
| * Creates a new instance. |
| * |
| * @param type type of the stream elements |
| */ |
| public CountOperator(DataSetType<Type> type) { |
| super(type, DataSetType.createDefault(Long.class), false); |
| } |
| |
| /** |
| * Creates a new instance. |
| * |
| * @param typeClass type of the stream elements |
| */ |
| public CountOperator(Class<Type> typeClass) { |
| this(DataSetType.createDefault(typeClass)); |
| } |
| |
| /** |
| * Copies an instance (exclusive of broadcasts). |
| * |
| * @param that that should be copied |
| */ |
| public CountOperator(CountOperator<Type> that) { |
| super(that); |
| } |
| |
| @Override |
| public Optional<CardinalityEstimator> createCardinalityEstimator( |
| final int outputIndex, |
| final Configuration configuration) { |
| Validate.inclusiveBetween(0, this.getNumOutputs() - 1, outputIndex); |
| return Optional.of(new FixedSizeCardinalityEstimator(1)); |
| } |
| } |