924060929 commented on code in PR #12996: URL: https://github.com/apache/doris/pull/12996#discussion_r996698062
########## fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/logical/PredicatePropagation.java: ########## @@ -0,0 +1,100 @@ +// 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.doris.nereids.rules.rewrite.logical; + +import org.apache.doris.nereids.trees.expressions.EqualTo; +import org.apache.doris.nereids.trees.expressions.Expression; +import org.apache.doris.nereids.trees.expressions.SlotReference; + +import com.google.common.collect.Lists; +import com.google.common.collect.Sets; + +import java.util.ArrayList; +import java.util.List; +import java.util.Set; + +/** + * derive additional predicates. + * for example: + * a = b and a = 1 => b = 1 + */ +public class PredicatePropagation { + + /** + * infer additional predicates. + */ + public Set<Expression> infer(List<Expression> predicates) { + Set<Expression> inferred = Sets.newHashSet(); + for (Expression predicate : predicates) { + if (canEquivalentDeduce(predicate)) { + List<Expression> candidates = subtract(predicates, predicate); + candidates.forEach(candidate -> { + inferred.add(transform(candidate, predicate.child(0), predicate.child(1))); + }); + } + } + predicates.forEach(inferred::remove); + return inferred; + } + + private Expression transform(Expression expression, Expression source, Expression target) { + Expression rewritten = replace(expression, source, target); + if (expression.equals(rewritten)) { + rewritten = mapChildren(expression, source, target); + if (expression.equals(rewritten)) { + return expression; + } else { + return rewritten; + } + } else { + return mapChildren(rewritten, source, target); + } + } + + private Expression mapChildren(Expression expression, Expression source, Expression target) { + if (!expression.children().isEmpty()) { + List<Expression> children = Lists.newArrayList(); + for (Expression child : expression.children()) { + children.add(transform(child, source, target)); + } + return expression.withChildren(children); + } else { + return expression; + } + } + + private Expression replace(Expression expression, Expression source, Expression target) { + if (expression.equals(source)) { + return target; + } + if (expression.equals(target)) { + return source; + } + return expression; + } + + private boolean canEquivalentDeduce(Expression predicate) { + return predicate instanceof EqualTo && predicate.children().stream().allMatch(e -> e instanceof SlotReference); + } + + private List<Expression> subtract(List<Expression> expressions, Expression target) { + ArrayList<Expression> cloneList = Lists.newArrayList(expressions); + cloneList.remove(target); + return cloneList; + } +} Review Comment: Do not recursively traverse/rewrite manually, too. Use DefaultExpressionRewriter: ```java class PredicatePropagation { public Set<Expression> infer(List<Expression> predicates) { Set<Expression> inferred = Sets.newHashSet(); for (Expression predicate : predicates) { if (canEquivalentDeduce(predicate)) { Expression leftSlotEqualToRightSlot = predicate; List<Expression> newInferred = predicates.stream() .filter(p -> !p.equals(leftSlotEqualToRightSlot)) .map(p -> doInfer(leftSlotEqualToRightSlot, p)) .collect(Collectors.toList()); inferred.addAll(newInferred); } } predicates.forEach(inferred::remove); return inferred; } private Expression doInfer(Expression leftSlotEqualToRightSlot, Expression expression) { return expression.accept(new DefaultExpressionRewriter<Void>() { @Override public Expression visit(Expression expr, Void context) { expr = super.visit(expr, context); // flip leftSlot and rightSlot if (expr.equals(leftSlotEqualToRightSlot.child(0))) { return expr.child(1); } else if (expr.equals(leftSlotEqualToRightSlot.child(1))) { return expr.child(0); } else { return expr; } } }, null); } private boolean canEquivalentDeduce(Expression predicate) { return predicate instanceof EqualTo && predicate.children().stream().allMatch(e -> e instanceof SlotReference); } ``` or you can add the common rewrite method to TreeNode: ```java /** * bottom-up rewrite. * @param rewriteFunction rewrite function. * @return rewritten result. */ default NODE_TYPE rewriteUp(Function<NODE_TYPE, NODE_TYPE> rewriteFunction) { boolean changed = false; Builder<NODE_TYPE> newChildren = ImmutableList.builderWithExpectedSize(arity()); for (NODE_TYPE child : children()) { NODE_TYPE newChild = child.rewriteUp(rewriteFunction); if (child != newChild) { changed = true; } newChildren.add(newChild); } NODE_TYPE rewrittenChildren = changed ? withChildren(newChildren.build()) : (NODE_TYPE) this; return rewriteFunction.apply(rewrittenChildren); } ``` then ```java private Expression doInfer(Expression leftSlotEqualToRightSlot, Expression expression) { return expression.rewriteUp(expr -> { if (expr.equals(leftSlotEqualToRightSlot.child(0))) { return expr.child(1); } else if (expr.equals(leftSlotEqualToRightSlot.child(1))) { return expr.child(0); } else { return expr; } }); } ``` -- This is an automated message from the Apache Git Service. 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