@Override
  public void visit(Select obj) {
    visitNodes(obj.getFrom());
    visitNodes(obj.getDerivedColumns());
    visitNode(obj.getWhere());
    visitNode(obj.getGroupBy());
    visitNode(obj.getHaving());
    visitNode(obj.getOrderBy());
    visitNode(obj.getLimit());

    if (this.doScanEvaluation) {
      HashMap<String, String> options =
          buildTableMetadata(
              this.scanTable.getName(), this.scanTable.getColumns(), this.ef.getEncoding());
      options.put(EvaluatorIterator.QUERYSTRING, SQLStringVisitor.getSQLString(obj.getWhere()));
      IteratorSetting it = new IteratorSetting(1, EvaluatorIterator.class, options);
      this.scanIterators.add(it);
    }

    if (this.selectColumns.size() < this.scanTable.getColumns().size()) {
      HashMap<String, String> options =
          buildTableMetadata(this.scanTable.getName(), this.selectColumns, this.ef.getEncoding());
      IteratorSetting it =
          new IteratorSetting(iteratorPriority++, LimitProjectionIterator.class, options);
      this.scanIterators.add(it);
    }
  }
  @Override
  public void execute() throws TranslatorException {

    LogManager.logTrace(
        LogConstants.CTX_CONNECTOR,
        "ObjectExecution command:",
        query.toString(),
        "using connection:",
        connection.getClass().getName()); // $NON-NLS-1$ //$NON-NLS-2$

    String nameInSource =
        getNameInSource(((NamedTable) query.getFrom().get(0)).getMetadataObject());

    List<Object> results = factory.search(query, nameInSource, connection, executionContext);

    if (results != null && results.size() > 0) {
      LogManager.logDetail(
          LogConstants.CTX_CONNECTOR,
          "ObjectExecution number of returned objects is :",
          results.size()); // $NON-NLS-1$

    } else {
      LogManager.logDetail(
          LogConstants.CTX_CONNECTOR,
          "ObjectExecution number of objects returned is : 0"); //$NON-NLS-1$

      results = Collections.emptyList();
    }

    this.resultsIt = results.iterator();
  }
  @Override
  public List<?> translateCommand(Command command, ExecutionContext context) {
    if (command instanceof Insert) {
      try {
        handleInsertSequences((Insert) command);
      } catch (TranslatorException e) {
        throw new RuntimeException(e);
      }
    }

    if (!(command instanceof QueryExpression)) {
      return null;
    }
    QueryExpression queryCommand = (QueryExpression) command;
    if (queryCommand.getLimit() == null) {
      return null;
    }
    Limit limit = queryCommand.getLimit();
    queryCommand.setLimit(null);

    if (command instanceof Select) {
      Select select = (Select) command;

      TableReference tr = select.getFrom().get(0);
      if (tr instanceof NamedTable && isDual((NamedTable) tr)) {
        if (limit.getRowOffset() > 0 || limit.getRowLimit() == 0) {
          // no data
          select.setWhere(
              new Comparison(
                  new Literal(1, TypeFacility.RUNTIME_TYPES.INTEGER),
                  new Literal(0, TypeFacility.RUNTIME_TYPES.INTEGER),
                  Operator.EQ));
          return null;
        }
        return null; // dual does not allow a limit
      }
    }

    List<Object> parts = new ArrayList<Object>();
    parts.add("SELECT "); // $NON-NLS-1$
    /*
     * if all of the columns are aliased, assume that names matter - it actually only seems to matter for
     * the first query of a set op when there is a order by.  Rather than adding logic to traverse up,
     * we just use the projected names
     */
    boolean allAliased = true;
    for (DerivedColumn selectSymbol : queryCommand.getProjectedQuery().getDerivedColumns()) {
      if (selectSymbol.getAlias() == null) {
        allAliased = false;
        break;
      }
    }
    if (allAliased) {
      String[] columnNames = queryCommand.getColumnNames();
      for (int i = 0; i < columnNames.length; i++) {
        if (i > 0) {
          parts.add(", "); // $NON-NLS-1$
        }
        parts.add(columnNames[i]);
      }
    } else {
      parts.add("*"); // $NON-NLS-1$
    }
    if (limit.getRowOffset() > 0) {
      parts.add(" FROM (SELECT VIEW_FOR_LIMIT.*, ROWNUM ROWNUM_ FROM ("); // $NON-NLS-1$
    } else {
      parts.add(" FROM ("); // $NON-NLS-1$
    }
    parts.add(queryCommand);
    if (limit.getRowOffset() > 0) {
      parts.add(") VIEW_FOR_LIMIT WHERE ROWNUM <= "); // $NON-NLS-1$
      parts.add(limit.getRowLimit() + limit.getRowOffset());
      parts.add(") WHERE ROWNUM_ > "); // $NON-NLS-1$
      parts.add(limit.getRowOffset());
    } else {
      parts.add(") WHERE ROWNUM <= "); // $NON-NLS-1$
      parts.add(limit.getRowLimit());
    }
    return parts;
  }