cloud-fan commented on a change in pull request #24559: URL: https://github.com/apache/spark/pull/24559#discussion_r587484940
########## File path: sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/functions/AggregateFunction.java ########## @@ -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.spark.sql.connector.catalog.functions; + +import org.apache.spark.sql.catalyst.InternalRow; +import org.apache.spark.sql.types.DataType; + +/** + * Interface for a function that produces a result value by aggregating over multiple input rows. + * <p> + * The JVM type of result values produced by this function must be the type used by Spark's + * InternalRow API for the {@link DataType SQL data type} returned by {@link #resultType()}. + * <p> + * Most implementations should also implement {@link PartialAggregateFunction} so that Spark can Review comment: Spark requires all aggregate functions to support partial merge, because the distributed aggregate operator in Spark requires it. As a result, even aggregate functions like `collect_list` have implemented the partial merging logic, though this doesn't make sense to them. I don't think Spark can change this in the near future, and the current two UDAF APIs in Spark(`UserDefinedAggregateFunction` and `Aggregator`) also require implementing partial merge. I think we need to do the same here. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
