viirya commented on a change in pull request #33352: URL: https://github.com/apache/spark/pull/33352#discussion_r676397731
########## File path: sql/catalyst/src/main/java/org/apache/spark/sql/connector/read/SupportsPushDownAggregates.java ########## @@ -0,0 +1,56 @@ +/* + * 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.read; + +import org.apache.spark.annotation.Evolving; +import org.apache.spark.sql.connector.expressions.Aggregation; + +/** + * A mix-in interface for {@link ScanBuilder}. Data sources can implement this interface to + * push down aggregates. Spark assumes that the data source can't fully complete the + * grouping work, and will group the data source output again. For queries like + * "SELECT min(value) AS m FROM t GROUP BY key", after pushing down the aggregate + * to the data source, the data source can still output data with duplicated keys, which is OK + * as Spark will do GROUP BY key again. The final query plan can be something like this: + * {{{ + * Aggregate [key#1], [min(min(value)#2) AS m#3] + * +- RelationV2[key#1, min(value)#2] + * }}} + * + * <p> + * Similarly, if there is no grouping expression, the data source can still output more than one + * rows. + * + * <p> + * When pushing down operators, Spark pushes down filters to the data source first, then push down + * aggregates or apply column pruning. Depends on data source implementation, aggregates may or + * may not be able to be pushed down with filters. If pushed filters still need to be evaluated + * after scanning, aggregates can't be pushed down. + * + * @since 3.2.0 + */ +@Evolving +public interface SupportsPushDownAggregates extends ScanBuilder { + + /** + * Pushes down Aggregation to datasource. The order of the datasource scan output columns should + * be: grouping columns, aggregate columns (in the same order as the aggregate functions in + * the given Aggregation). + */ + boolean pushAggregation(Aggregation aggregation); Review comment: For public API, we should document what the returned value means. -- 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. To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org
