| // 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.impala.rewrite; |
| |
| import org.apache.impala.analysis.Analyzer; |
| import org.apache.impala.analysis.BinaryPredicate; |
| import org.apache.impala.analysis.BoolLiteral; |
| import org.apache.impala.analysis.Expr; |
| |
| /** |
| * Simplifies DISTINCT FROM and NOT DISTINCT FROM predicates |
| * where the arguments are identical expressions. |
| * |
| * x IS DISTINCT FROM x -> false |
| * x IS NOT DISTINCT FROM x -> true |
| * |
| * Note that "IS NOT DISTINCT FROM" and the "<=>" are the same. |
| */ |
| public class SimplifyDistinctFromRule implements ExprRewriteRule { |
| public static ExprRewriteRule INSTANCE = new SimplifyDistinctFromRule(); |
| |
| @Override |
| public Expr apply(Expr expr, Analyzer analyzer) { |
| if (!expr.isAnalyzed()) return expr; |
| |
| if (expr instanceof BinaryPredicate) { |
| BinaryPredicate pred = (BinaryPredicate) expr; |
| if (pred.getOp() == BinaryPredicate.Operator.NOT_DISTINCT) { |
| if (pred.getChild(0).equals(pred.getChild(1))) { |
| return new BoolLiteral(true); |
| } |
| } |
| if (pred.getOp() == BinaryPredicate.Operator.DISTINCT_FROM) { |
| if (pred.getChild(0).equals(pred.getChild(1))) { |
| return new BoolLiteral(false); |
| } |
| } |
| } |
| return expr; |
| } |
| } |