public boolean hasTableAlias(String tab_alias) {
    return rslvMap.get(tab_alias.toLowerCase()) != null;
  }
Puts a resolver entry corresponding to the expression and its
column alias which is used for alias recognition in the latter constructs
@param exprToColumnAlias
         The map containing the expression to alias mapping
@throws SemanticException
ql/src/java/org/apache/hadoop/hive/ql/parse/RowResolver.java