[GitHub] [calcite] chunweilei commented on a change in pull request #1724: [CALCITE-3675] SQL to Rel conversion is broken for coalesce on nullable field

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chunweilei commented on a change in pull request #1724: [CALCITE-3675] SQL to Rel conversion is broken for coalesce on nullable field
URL: https://github.com/apache/calcite/pull/1724#discussion_r363570799
 
 

 ##########
 File path: core/src/main/java/org/apache/calcite/sql/fun/SqlCaseOperator.java
 ##########
 @@ -293,16 +294,26 @@ private RelDataType inferTypeFromValidator(
     return ret;
   }
 
-  private RelDataType inferTypeFromOperands(
-      RelDataTypeFactory typeFactory,
-      List<RelDataType> argTypes) {
+  private RelDataType inferTypeFromOperands(SqlOperatorBinding opBinding) {
+    final RelDataTypeFactory typeFactory = opBinding.getTypeFactory();
+    final List<RelDataType> argTypes = opBinding.collectOperandTypes();
     assert (argTypes.size() % 2) == 1 : "odd number of arguments expected: "
         + argTypes.size();
     assert argTypes.size() > 1 : "CASE must have more than 1 argument. Given "
       + argTypes.size() + ", " + argTypes;
     List<RelDataType> thenTypes = new ArrayList<>();
     for (int j = 1; j < (argTypes.size() - 1); j += 2) {
-      thenTypes.add(argTypes.get(j));
+      RelDataType argType = argTypes.get(j);
+      if (opBinding instanceof RexCallBinding) {
+        RexNode whenNode = ((RexCallBinding) opBinding).getOperands().get(j - 1);
+        RexNode thenNode = ((RexCallBinding) opBinding).getOperands().get(j);
+        if (whenNode.getKind() == SqlKind.IS_NOT_NULL && argType.isNullable()) {
+          if (((RexCall) whenNode).getOperands().get(0).equals(thenNode)) {
 
 Review comment:
   It might be better if we put the if condition out of the loop.

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