asolimando commented on code in PR #4592:
URL: https://github.com/apache/calcite/pull/4592#discussion_r2449002181
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core/src/main/java/org/apache/calcite/sql/type/SqlTypeUtil.java:
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@@ -178,12 +179,59 @@ public static boolean isCharTypeComparable(
return true;
}
+ /** A namespace may contain multiple fields with the same name.
+ * However, a proper ROW type cannot; this function will assign
+ * unique names to fields when they are used to build a concrete ROW type.
+ *
+ * @param type A type for which type.isStruct() is true.
+ * @return A new version of this type where all fields have unique names.
+ *
+ * <p>Note: the same rule to rename fields is used by the {@link
SqlToRelConverter} later,
+ * in convertNonAggregateSelectList (a private method). This ensures that
+ * the generated field names there will match with the inferred field names
here.
+ */
+ private static RelDataType uniquify(RelDataTypeFactory factory, RelDataType
type) {
+ List<String> unique = SqlValidatorUtil.uniquify(type.getFieldNames(),
true);
+ List<RelDataType> types = type.getFieldList()
+ .stream()
+ .map(RelDataTypeField::getType)
+ .collect(Collectors.toList());
+ return factory.createStructType(type.getStructKind(), types, unique);
+ }
+
+ /**
+ * Derives component type for ARRAY, MULTISET, MAP when input is sub-query.
+ *
+ * @param factory Type factory used to generate new types if necessary
+ * @param origin original component type
+ * @return component type
+ */
+ public static RelDataType deriveCollectionQueryComponentType(
+ RelDataTypeFactory factory,
+ SqlTypeName collectionType,
+ RelDataType origin) {
+ switch (collectionType) {
+ case ARRAY:
+ case MULTISET:
+ return origin.isStruct() && origin.getFieldCount() == 1
+ ? origin.getFieldList().get(0).getType() : uniquify(factory, origin);
+ case MAP:
+ return origin;
+ default:
+ throw new AssertionError(
+ "Impossible to derive component type for " + collectionType);
+ }
+ }
+
/**
* Derives component type for ARRAY, MULTISET, MAP when input is sub-query.
*
* @param origin original component type
* @return component type
+ * @deprecated Use
Review Comment:
This is cool, I didn't know it existed, I am always annoyed by deprecations
that don't point you to what you should use instead, this is a nice way to do
that!
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