| /** |
| * 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.apex.malhar.lib.dimensions.aggregator; |
| |
| import org.apache.apex.malhar.lib.dimensions.DimensionsConversionContext; |
| import org.apache.apex.malhar.lib.dimensions.DimensionsEvent.Aggregate; |
| import org.apache.apex.malhar.lib.dimensions.DimensionsEvent.InputEvent; |
| import org.apache.apex.malhar.lib.dimensions.aggregator.AggregateEvent.Aggregator; |
| |
| import com.datatorrent.lib.appdata.schemas.FieldsDescriptor; |
| import com.datatorrent.lib.appdata.schemas.Type; |
| |
| /** |
| * <p> |
| * {@link IncrementalAggregator}s perform aggregations in place, on a field by field basis. For example if we have a |
| * field cost, an incremental aggregator would take a new value of cost and aggregate it to an aggregate value for |
| * cost. No fields except the cost field are used in the computation of the cost aggregation in the case of an |
| * {@link IncrementalAggregator}. |
| * </p> |
| * <p> |
| * {@link IncrementalAggregator}s are intended to be used with subclasses of |
| * {@link com.datatorrent.lib.dimensions.AbstractDimensionsComputationFlexibleSingleSchema}. The way in which |
| * {@link IncrementalAggregator}s are used in this context is that a batch of fields to be aggregated by the aggregator |
| * are provided in the form of an {@link InputEvent}. For example, if there are two fields (cost and revenue), which |
| * will be aggregated by a sum aggregator, both of those fields will be included in the {@link InputEvent} passed to |
| * the sum aggregator. And the {DimensionsEventregate} event produced by the sum aggregator will contain two fields, |
| * one for cost and one for revenue. |
| * </p> |
| * |
| * |
| * @since 3.4.0 |
| */ |
| public interface IncrementalAggregator extends Aggregator<InputEvent, Aggregate> |
| { |
| /** |
| * This method defines the type mapping for the {@link IncrementalAggregator}. The type mapping defines the |
| * relationship between the type of an input field and the type of its aggregate. For example if the aggregator takes |
| * a field of type int and produces an aggregate of type float, then this method would return a type of float when |
| * the given input type is an int. |
| * @param inputType The type of a field to be aggregate. |
| * @return The type of the aggregate corresponding to an input field of the given type. |
| */ |
| public Type getOutputType(Type inputType); |
| |
| /** |
| * This sets |
| */ |
| public void setDimensionsConversionContext(DimensionsConversionContext context); |
| |
| /** |
| * Returns a {@link FieldsDescriptor} object which describes the meta data that is stored along with aggregations. |
| * This method returns null if this aggregator stores no metadata. |
| * @return A {@link FieldsDescriptor} object which describes the meta data that is stored along with aggregations. |
| * This method returns null if this aggregator stores no metadata. |
| */ |
| public FieldsDescriptor getMetaDataDescriptor(); |
| } |