danny0405 commented on a change in pull request #2016: URL: https://github.com/apache/calcite/pull/2016#discussion_r439280300
########## File path: core/src/main/java/org/apache/calcite/plan/Digest.java ########## @@ -0,0 +1,245 @@ +/* + * 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.calcite.plan; + +import org.apache.calcite.plan.hep.HepRelVertex; +import org.apache.calcite.plan.volcano.RelSubset; +import org.apache.calcite.rel.RelNode; +import org.apache.calcite.rel.hint.Hintable; +import org.apache.calcite.rel.type.RelDataType; +import org.apache.calcite.util.Pair; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.List; +import java.util.Objects; + +/** + * A short description of relational expression's type, inputs, and + * other properties. The digest uniquely identifies the node; another node + * is equivalent if and only if it has the same value. + * + * <p>Row type is part of the digest for the rare occasion that similar + * expressions have different types, e.g. variants of + * {@code Project(child=rel#1, a=null)} where a is a null INTEGER or a + * null VARCHAR(10). Row type is represented as fieldTypes only, so {@code RelNode} + * that differ with field names only are treated equal. + * For instance, {@code Project(input=rel#1,empid=$0)} and {@code Project(input=rel#1,deptno=$0)} + * are equal. + * + * <p>Computed by {@code org.apache.calcite.rel.AbstractRelNode#computeDigest}, + * assigned by {@link org.apache.calcite.rel.AbstractRelNode#onRegister}, + * returned by {@link org.apache.calcite.rel.AbstractRelNode#getDigest()}. + */ +public class Digest implements Comparable<Digest> { + + //~ Instance fields -------------------------------------------------------- + + final int hashCode; + final List<Pair<String, Object>> items; + private final RelNode rel; + + // Used for debugging, computed lazily. + private String digest = null; + + //~ Constructors ----------------------------------------------------------- + + /** + * Creates a digest with given rel and properties. + * + * @param rel The rel + * @param items The properties, e.g. the inputs, the type, the traits and so on + */ + private Digest(RelNode rel, List<Pair<String, Object>> items) { + this.rel = rel; + this.items = normalizeContents(items); + this.hashCode = computeIdentity(rel, this.items); + } + + /** + * Creates a digest with given rel, the digest is computed as simple, + * see {@link #simpleRelDigest(RelNode)}. + */ + private Digest(RelNode rel) { + this(rel, simpleRelDigest(rel)); + } + + /** Creates a digest with given rel and string format digest. */ + private Digest(RelNode rel, String digest) { + this.rel = rel; + this.items = Collections.emptyList(); + this.digest = digest; + this.hashCode = this.digest.hashCode(); + } + + /** Returns the identity of this digest which is used to speedup hashCode and equals. */ + private static int computeIdentity(RelNode rel, List<Pair<String, Object>> contents) { + return Objects.hash(collect(rel, contents)); + } + + private static Object[] collect(RelNode rel, List<Pair<String, Object>> contents) { Review comment: Finally i decide to keep it as is, because the conflict is very few, i also remove the row type when computing hashcode, because row type diff for equiv node is also rare case(usually because of nullability changes). ---------------------------------------------------------------- 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
