[GitHub] [calcite] danny0405 commented on a change in pull request #2246: [CALCITE-4377] Fix the return nullability inference during rex simpli…

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danny0405 commented on a change in pull request #2246:
URL: https://github.com/apache/calcite/pull/2246#discussion_r521969779



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File path: core/src/main/java/org/apache/calcite/rex/RexSimplify.java
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@@ -900,13 +902,12 @@ private void validateStrongPolicy(RexNode rexNode) {
     case ANY:
       List<RexNode> operands = ((RexCall) rexNode).getOperands();
       if (rexNode.getType().isNullable()) {
-        assert operands.stream()
-            .map(RexNode::getType)
-            .anyMatch(RelDataType::isNullable);
+        // Ignores the nullability change when all the operands are literals
+        // which come from the simplification.
+        assert operands.stream().map(RexNode::getType).anyMatch(RelDataType::isNullable)
+            || operands.stream().allMatch(p -> RexUtil.isLiteral(p, false));

Review comment:
       During the simplification, we drop the useless case `cast(1 as nullable INT)` which breaks the nullability. We have 2 choices:
   1. Do not make any simplification that breaks the nullability
   2. Make the validation strategy more relaxed
   
   I choose the latter.




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