rdblue commented on a change in pull request #924: Add void transform that always produces null URL: https://github.com/apache/incubator-iceberg/pull/924#discussion_r409093584
########## File path: api/src/main/java/org/apache/iceberg/transforms/VoidTransform.java ########## @@ -0,0 +1,76 @@ +/* + * 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.iceberg.transforms; + +import java.io.ObjectStreamException; +import org.apache.iceberg.expressions.BoundPredicate; +import org.apache.iceberg.expressions.UnboundPredicate; +import org.apache.iceberg.types.Type; + +class VoidTransform<S> implements Transform<S, Void> { + private static final VoidTransform<Object> INSTANCE = new VoidTransform<>(); + + @SuppressWarnings("unchecked") + static <T> VoidTransform<T> get() { + return (VoidTransform<T>) INSTANCE; + } + + private VoidTransform() { + } + + @Override + public Void apply(Object value) { + return null; + } + + @Override + public boolean canTransform(Type type) { + return true; + } + + @Override + public Type getResultType(Type sourceType) { + return sourceType; + } + + @Override + public UnboundPredicate<Void> projectStrict(String name, BoundPredicate<S> predicate) { + return null; + } + + @Override + public UnboundPredicate<Void> project(String name, BoundPredicate<S> predicate) { + return null; + } + + @Override + public String toHumanString(Void value) { + return "null"; + } + + @Override + public String toString() { + return "void"; + } Review comment: Null is the human-readable string for the value produced by the transform. Void is the name of the transform. I considered naming it something like `always_null` but `void` seemed shorter and less error prone (was that alwaysNull or always-null?) ---------------------------------------------------------------- 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 --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
