KurtYoung commented on a change in pull request #8003: [FLINK-11951][table-common] Enhance UserDefinedFunction interface to allow more user defined types URL: https://github.com/apache/flink/pull/8003#discussion_r266741891
########## File path: flink-table/flink-table-common/src/main/java/org/apache/flink/table/functions/CustomTypeDefinedFunction.java ########## @@ -0,0 +1,110 @@ +/* + * 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; + +import org.apache.flink.api.common.functions.InvalidTypesException; +import org.apache.flink.api.common.typeinfo.TypeInformation; +import org.apache.flink.api.java.typeutils.TypeExtractor; +import org.apache.flink.table.api.ValidationException; + +/** + * {@link UserDefinedFunction} to define its parameterTypes. + */ +public abstract class CustomTypeDefinedFunction extends UserDefinedFunction { + + /** + * Returns {@link TypeInformation} about the operands of the evaluation method with a given + * signature. + * + * <p>In order to perform operand type inference in SQL (especially when <code>NULL</code> is + * used) it might be necessary to determine the parameter {@link TypeInformation} of an + * evaluation method. By default Flink's type extraction facilities are used for this but might + * be wrong for more complex, custom, or composite types. + * + * @param signature signature of the method the operand types need to be determined + * @return {@link TypeInformation} of operand types + */ + public TypeInformation<?>[] getParameterTypes(Class<?>[] signature) { + final TypeInformation<?>[] types = new TypeInformation<?>[signature.length]; + for (int i = 0; i < signature.length; i++) { + try { + types[i] = TypeExtractor.getForClass(signature[i]); + } catch (InvalidTypesException e) { + throw new ValidationException( + "Parameter types of scalar function " + this.getClass().getCanonicalName() + + " cannot be automatically determined. Please provide type information manually."); + } + } + return types; + } + + /** + * Returns the result type of the evaluation method with a given signature. + * + * <p>This method needs to be overriden in case Flink's type extraction facilities are not + * sufficient to extract the {@link TypeInformation} based on the return type of the evaluation + * method. Flink's type extraction facilities can handle basic types or + * simple POJOs but might be wrong for more complex, custom, or composite types. + * + * <p>The input arguments are the input arguments which are passed to the eval() method. + * Only the literal arguments (constant values) are passed to the {@link #getResultType()} method. + * If non-literal arguments appear, it will pass nulls instead. + * + * <p>The argument types are also passed to the method. These argument types would allow to + * determine the return type based on the used eval() method. + * + * @param arguments arguments of a function call (only literal arguments + * are passed, nulls for non-literal ones) + * @param argTypes The classes of the arguments of the called eval() method. + * @return {@link TypeInformation} of result type or null if Flink should determine the type + */ + public TypeInformation<?> getResultType(Object[] arguments, Class<?>[] argTypes) { Review comment: I'm not sure we extend the API and throw an exception in one runner is a good choice.. ---------------------------------------------------------------- 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: us...@infra.apache.org With regards, Apache Git Services
