class ColumnReferenceValidator {

  Set<SourceName> analyzeExpression(
      final Expression expression,
      final String clauseType
  ) {
    final Validator extractor = new Validator(clauseType);
    extractor.process(expression, null);
    return extractor.referencedSources;
  }

    ColumnReferenceValidator(
      final SourceSchemas sourceSchemas,
      final boolean possibleSyntheticColumns
  );

}