@Override
  public Set<ReadEntity> getAllInputs() {
    Set<ReadEntity> readEntities = new HashSet<ReadEntity>(getInputs());
    for (CTEClause cte : rootClause.asExecutionOrder()) {
      if (cte.source != null) {
        readEntities.addAll(cte.source.getInputs());
      }
    }
    return readEntities;
  }
Goes though the tabref tree and finds the alias for the table. Once found,
it records the table name-> alias association in aliasToTabs. It also makes
an association from the alias to the table AST in parse info.

@return the alias of the table
ql/src/java/org/apache/hadoop/hive/ql/parse/SemanticAnalyzer.java