private boolean isAmbiguousReference(String tableAlias, String colAlias) {

    if(!getCheckForAmbiguity()) {
      return false;
    }
    if(ambiguousColumns == null || ambiguousColumns.isEmpty()) {
      return false;
    }

    if(tableAlias != null) {
      Map<String, String> colAliases = ambiguousColumns.get(tableAlias.toLowerCase());
      if(colAliases != null && colAliases.containsKey(colAlias.toLowerCase())) {
        return true;
      }
    } else {
      for (Map.Entry<String, Map<String, String>> ambiguousColsEntry: ambiguousColumns.entrySet()) {
        Map<String, String> cmap = ambiguousColsEntry.getValue();
        for (Map.Entry<String, String> cmapEnt : cmap.entrySet()) {
          if (colAlias.equalsIgnoreCase(cmapEnt.getKey())) {
            return true;
          }
        }
      }
    }
    return false;
  }
Return a new row resolver that is combination of left RR and right RR.
The schema will be schema of left, schema of right

@param leftRR
@param rightRR
@return
@throws SemanticException
ql/src/java/org/apache/hadoop/hive/ql/parse/RowResolver.java