szehon-ho commented on code in PR #45267: URL: https://github.com/apache/spark/pull/45267#discussion_r1530840650
########## sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/functions/ReducibleFunction.java: ########## @@ -0,0 +1,72 @@ +/* + * 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.annotation.Evolving; +import scala.Option; + +/** + * Base class for user-defined functions that can be 'reduced' on another function. + * + * A function f_source(x) is 'reducible' on another function f_target(x) if + * there exists a reducer function r(x) such that r(f_source(x)) = f_target(x) for all input x. + * + * <p> + * Examples: + * <ul> + * <li>Bucket functions + * <ul> + * <li>f_source(x) = bucket(4, x)</li> + * <li>f_target(x) = bucket(2, x)</li> + * <li>r(x) = x / 2</li> + * </ul> + * <li>Date functions + * <ul> + * <li>f_source(x) = days(x)</li> + * <li>f_target(x) = hours(x)</li> + * <li>r(x) = x / 24</li> + * </ul> + * </ul> + * @param <I> reducer function input type + * @param <O> reducer function output type + * @since 4.0.0 + */ +@Evolving +public interface ReducibleFunction<I, O> { + + /** + * If this function is 'reducible' on another function, return the {@link Reducer} function. + * <p> + * Example: + * <ul> + * <li>this_function = bucket(4, x) + * <li>other function = bucket(2, x) + * </ul> + * Invoke with arguments + * <ul> + * <li>other = bucket</li> + * <li>this param = Int(4)</li> + * <li>other param = Int(2)</li> + * </ul> + * @param other the other function + * @param thisParam param for this function Review Comment: Actually on second thought, we do plan to add geo partition transforms , for example xz2 ordering https://github.com/spatialx-project/geolake/blob/main/api/src/main/java/org/apache/iceberg/transforms/ExtendedZCurve.java which need resolution. as well as multi-arg bucket transforms: https://docs.google.com/document/d/1aDoZqRgvDOOUVAGhvKZbp5vFstjsAMY4EFCyjlxpaaw/ So i added back the type to Object in latest pr, hope it is ok. Note, I tried awhile to make the method type-parameterized like ``` <T> Option<Reducer<I, O>> reducer(ReducibleFunction<I, O> other, T numBuckets, T otherNumBuckets); ``` but was not able to override it successfully in Bucket in scala -- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
