[GitHub] vlsi commented on a change in pull request #1044: [CALCITE-2838] Simplification: Remove redundant IS TRUE/IS NOT FALSE …

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vlsi commented on a change in pull request #1044: [CALCITE-2838] Simplification: Remove redundant IS TRUE/IS NOT FALSE …
URL: https://github.com/apache/calcite/pull/1044#discussion_r256836978
 
 

 ##########
 File path: core/src/main/java/org/apache/calcite/rex/RexSimplify.java
 ##########
 @@ -494,10 +494,16 @@ private RexNode simplifyNot(RexCall call, RexUnknownAs unknownAs) {
     return call;
   }
 
-  private RexNode simplifyIs(RexCall call) {
+  private RexNode simplifyIs(RexCall call, RexUnknownAs unknownAs) {
     final SqlKind kind = call.getKind();
-    final RexNode a = call.getOperands().get(0);
-
+    final RexNode argument = call.getOperands().get(0);
+    if (kind == SqlKind.IS_TRUE && unknownAs == RexUnknownAs.FALSE) {
+      return simplify(argument, unknownAs);
+    }
+    if (kind == SqlKind.IS_NOT_FALSE && unknownAs == RexUnknownAs.TRUE) {
+      return simplify(argument, unknownAs);
+    }
+    final RexNode a = simplify(call.getOperands().get(0), RexUnknownAs.UNKNOWN);
 
 Review comment:
   This does look like `O(N^2)`.
   Can you please avoid simplifying the same nodes again and again?

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