[GitHub] [calcite] julianhyde commented on a change in pull request #2272: [CALCITE-4409] Improve exception when RelBuilder tries to create a field on a non-struct expression

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julianhyde commented on a change in pull request #2272:
URL: https://github.com/apache/calcite/pull/2272#discussion_r530460652



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File path: core/src/main/java/org/apache/calcite/rel/type/RelDataTypeImpl.java
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@@ -79,6 +79,10 @@ protected RelDataTypeImpl() {
 
   @Override public RelDataTypeField getField(String fieldName, boolean caseSensitive,
       boolean elideRecord) {
+    if (fieldList == null) {
+      throw new IllegalStateException("Requested field " + fieldName
+          + " in a type with null fieldList, type = " + this);

Review comment:
       I’d prefer a simpler error message, such as “Type does not support fields”. Especially if it’s emitted by RelDataType, which is a low level class and not supposed to be user-friendly.




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