rdblue commented on a change in pull request #24559: URL: https://github.com/apache/spark/pull/24559#discussion_r587667679
########## File path: sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/functions/BoundFunction.java ########## @@ -0,0 +1,88 @@ +/* + * 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.types.DataType; +import org.apache.spark.sql.types.IntegerType; + +import java.io.Serializable; +import java.util.UUID; + +/** + * Represents a function that is bound to an input type. + */ +public interface BoundFunction extends Function, Serializable { + + /** + * Returns the {@link DataType data type} of values produced by this function. + * <p> + * For example, a "plus" function may return {@link IntegerType} when it is bound to arguments + * that are also {@link IntegerType}. + * + * @return a data type for values produced by this function + */ + DataType resultType(); + + /** + * Returns the whether values produced by this function may be null. + * <p> + * For example, a "plus" function may return false when it is bound to arguments that are always + * non-null, but true when either argument may be null. + * + * @return true if values produced by this function may be null, false otherwise + */ + default boolean isResultNullable() { + return true; + } + + /** + * Returns whether this function result is deterministic. + * <p> + * By default, functions are assumed to be deterministic. Functions that are not deterministic + * should override this method so that Spark can ensure the function runs only once for a given + * input. + * + * @return true if this function is deterministic, false otherwise + */ + default boolean isDeterministic() { + return true; + } + + /** + * Returns the canonical name of this function, used to determine if functions are equivalent. + * <p> + * The canonical name is used to determine whether two functions are the same when loaded by + * different catalogs. For example, the same catalog implementation may be used for by two + * environments, "prod" and "test". Functions produced by the catalogs may be equivalent, but + * loaded using different names, like "test.func_name" and "prod.func_name". + * <p> + * Names returned by this function should be unique and unlikely to conflict with similar + * functions in other catalogs. For example, many catalogs may define a "bucket" function with a + * different implementation. Adding context, like "com.mycompany.bucket(string)", is recommended + * to avoid unintentional collisions. + * + * @return a canonical name for this function + */ + default String canonicalName() { + // by default, use a random UUID so a function is never equivalent to another, even itself. + // this method is not required so that generated implementations (or careless ones) are not + // added and forgotten. for example, returning "" as a place-holder could cause unnecessary + // bugs if not replaced before release. + return UUID.randomUUID().toString(); + } Review comment: I have no problem adding it now. It just adds complexity to what we need to think through and document. Do we support any cast or only safe casts? If a value can't be cast, do we pass null like ANSI behavior? ---------------------------------------------------------------- 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]
