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ASF GitHub Bot commented on FLINK-5767: --------------------------------------- Github user fhueske commented on a diff in the pull request: https://github.com/apache/flink/pull/3354#discussion_r102220814 --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/AggregateFunction.scala --- @@ -0,0 +1,73 @@ +/* + * 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.flink.table.functions + +/** + * Base class for User-Defined Aggregates. + * + * @tparam T the type of the aggregation result + */ +abstract class AggregateFunction[T] extends UserDefinedFunction { + /** + * Create and init the Accumulator for this [[AggregateFunction]]. + * + * @return the accumulator with the initial value + */ + def createAccumulator(): Accumulator + + /** + * Called every time when an aggregation result should be materialized. + * The returned value could be either a speculative result (periodically + * emitted as data arrive) or the final result of the aggregation (when + * the state of the aggregation is completely removed). --- End diff -- How would the function distinguish these cases? I think we should not mention that the state is removed because it is not the responsibility of the method. > New aggregate function interface and built-in aggregate functions > ----------------------------------------------------------------- > > Key: FLINK-5767 > URL: https://issues.apache.org/jira/browse/FLINK-5767 > Project: Flink > Issue Type: Sub-task > Components: Table API & SQL > Reporter: Shaoxuan Wang > Assignee: Shaoxuan Wang > > Add a new aggregate function interface. This includes implementing the > aggregate interface, migrating the existing aggregation functions to this > interface, and adding the unit tests for these functions. -- This message was sent by Atlassian JIRA (v6.3.15#6346)