dawidwys commented on a change in pull request #8865: [FLINK-12924][table] Introduce basic type inference interfaces URL: https://github.com/apache/flink/pull/8865#discussion_r297085641
########## File path: flink-table/flink-table-common/src/main/java/org/apache/flink/table/types/inference/TypeInference.java ########## @@ -0,0 +1,183 @@ +/* + * 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.types.inference; + +import org.apache.flink.annotation.PublicEvolving; +import org.apache.flink.table.types.DataType; +import org.apache.flink.util.Preconditions; + +import javax.annotation.Nullable; + +import java.util.List; +import java.util.Optional; + +/** + * Provides logic for the type inference of function calls. It includes: + * <ul> + * <li>explicit input specification for (possibly named) arguments</li> + * <li>inference of missing input types</li> + * <li>validation of input types</li> + * <li>inference of an intermediate accumulation type</li> + * <li>inference of the final output type</li> + * </ul> + * + * <p>See {@link TypeInferenceUtil} for more information about the type inference process. + */ +@PublicEvolving +public class TypeInference { + + private final InputTypeValidator inputTypeValidator; + + private final TypeStrategy accumulatorTypeStrategy; + + private final TypeStrategy outputTypeStrategy; + + private final @Nullable List<String> argumentNames; + + private final @Nullable List<DataType> argumentTypes; + + private TypeInference( + InputTypeValidator inputTypeValidator, + TypeStrategy accumulatorTypeStrategy, + TypeStrategy outputTypeStrategy, + @Nullable List<String> argumentNames, + @Nullable List<DataType> argumentTypes) { + this.inputTypeValidator = inputTypeValidator; + this.accumulatorTypeStrategy = outputTypeStrategy; + this.outputTypeStrategy = outputTypeStrategy; + if (argumentNames != null && argumentTypes != null && argumentNames.size() != argumentTypes.size()) { + throw new IllegalArgumentException( + String.format( + "Mismatch between argument types %d and argument names %d.", + argumentNames.size(), + argumentTypes.size())); + } + this.argumentNames = argumentNames; + this.argumentTypes = argumentTypes; + } + + public InputTypeValidator getInputTypeValidator() { + return inputTypeValidator; + } + + public TypeStrategy getAccumulatorTypeStrategy() { + return accumulatorTypeStrategy; + } + + public TypeStrategy getOutputTypeStrategy() { + return outputTypeStrategy; + } + + public Optional<List<String>> getArgumentNames() { + return Optional.ofNullable(argumentNames); + } + + public Optional<List<DataType>> getArgumentTypes() { + return Optional.ofNullable(argumentTypes); + } + + // -------------------------------------------------------------------------------------------- + + /** + * Builder for configuring and creating instances of {@link TypeInference}. + */ + public static class Builder { + + private InputTypeValidator inputTypeValidator = InputTypeValidators.PASSING; + + private @Nullable TypeStrategy accumulatorTypeStrategy; + + private @Nullable TypeStrategy outputTypeStrategy; + + private @Nullable List<String> argumentNames; + + private @Nullable List<DataType> argumentTypes; + + public Builder() { + // default constructor to allow a fluent definition + } + + /** + * Sets the validator for checking the input data types of a function call. + * + * <p>A always passing function is assumed by default (see {@link InputTypeValidators#PASSING}). + */ + public Builder inputTypeValidator(InputTypeValidator inputTypeValidator) { + this.inputTypeValidator = + Preconditions.checkNotNull(inputTypeValidator, "Input type validator must not be null."); + return this; + } + + /** + * Sets the strategy for inferring the intermediate accumulator data type of a function call. + * + * <p>By default the accumulator type is assumed to be equal to the output type strategy (see + * {@link #outputTypeStrategy(TypeStrategy)}). + */ + public Builder accumulatorTypeStrategy(TypeStrategy accumulatorTypeStrategy) { + this.accumulatorTypeStrategy = + Preconditions.checkNotNull(accumulatorTypeStrategy, "Accumulator type strategy must not be null."); + return this; + } + + /** + * Sets the strategy for inferring the final output data type of a function call. + * + * <p>Required. + */ + public Builder outputTypeStrategy(TypeStrategy outputTypeStrategy) { Review comment: Personal taste, so feel free to ignore as we never had a proper discussion on design patterns standards. Personally, in most cases, I prefer to have a static factory method with the required parameter(s). In this case I would prefer `public static Builder TypeInference#outputTypeStrategy(TypeStrategy outputTypeStrategy)`, but as I said this is just a personal taste. ---------------------------------------------------------------- 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] With regards, Apache Git Services
