[GitHub] [calcite] danny0405 commented on a change in pull request #1610: [CALCITE-3525] RexSimplify: eliminate redundant rex calls in OR

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danny0405 commented on a change in pull request #1610: [CALCITE-3525] RexSimplify: eliminate redundant rex calls in OR
URL: https://github.com/apache/calcite/pull/1610#discussion_r352262329
 
 

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 File path: core/src/main/java/org/apache/calcite/rel/rules/FilterProjectTransposeRule.java
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 @@ -202,8 +202,9 @@ private RexNode simplifyFilterCondition(RexNode condition, RelOptRuleCall call)
     // 1>null evaluates to unknown and WHERE unknown behaves exactly like WHERE false
     RexSimplify simplifier =
         new RexSimplify(xBuilder, RelOptPredicateList.EMPTY, executor);
-    return RexUtil.removeNullabilityCast(
+    RexNode simplified = RexUtil.removeNullabilityCast(
         xBuilder.getTypeFactory(), simplifier.simplifyUnknownAsFalse(condition));
+    return simplified.isAlwaysFalse() ? condition : simplified;
 
 Review comment:
   Why we returns the original condition if the simplified node is always false ? Shouldn't we just return the simplified one ?

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