[GitHub] [incubator-doris] yangzhg commented on a diff in pull request #9018: [feature](optimizer): rewrite expr self compare

[GitBox <gi...@apache.org>]

yangzhg commented on code in PR #9018:
URL: https://github.com/apache/incubator-doris/pull/9018#discussion_r851104994


##########
fe/fe-core/src/main/java/org/apache/doris/rewrite/RewriteSelfCmpRule.java:
##########
@@ -0,0 +1,57 @@
+// 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.rewrite;
+
+import org.apache.doris.analysis.Analyzer;
+import org.apache.doris.analysis.BinaryPredicate;
+import org.apache.doris.analysis.BoolLiteral;
+import org.apache.doris.analysis.Expr;
+import org.apache.doris.analysis.IsNullPredicate;
+import org.apache.doris.analysis.SlotRef;
+import org.apache.doris.common.AnalysisException;
+
+/**
+ * Rewrites predicate which is self compare self like A = A.
+ * =, >= , <=: where col is not null;
+ * <, >, !=: where false;
+ * <=>: where true;
+ */
+public class RewriteSelfCmpRule implements ExprRewriteRule {
+    public static ExprRewriteRule INSTANCE = new RewriteSelfCmpRule();
+
+    @Override
+    public Expr apply(Expr expr, Analyzer analyzer, ExprRewriter.ClauseType clauseType) throws AnalysisException {
+        if (!(expr instanceof BinaryPredicate) || !(expr.getChild(0) instanceof SlotRef)
+                || !expr.getChild(0).equals(expr.getChild(1)))
+            return expr;
+
+        switch (((BinaryPredicate) expr).getOp()) {
+            case EQ:
+            case LE:
+            case GE:
+                return new IsNullPredicate(expr.getChild(0), true);
+            case NE:

Review Comment:
   if expr is null , null != null return null not false



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