def get_columns(self, with_aliases=False):
        """
        Returns the list of columns to use in the select statement, as well as
        a list any extra parameters that need to be included. If no columns
        have been specified, returns all columns relating to fields in the
        model.

        If 'with_aliases' is true, any column names that are duplicated
        (without the table names) are given unique aliases. This is needed in
        some cases to avoid ambiguity with nested queries.
        """
        qn = self.quote_name_unless_alias
        qn2 = self.connection.ops.quote_name
        result = ['(%s) AS %s' - (col[0], qn2(alias)) for alias, col in six.iteritems(self.query.extra_select)]
        params = []
        aliases = set(self.query.extra_select.keys())
        if with_aliases:
            col_aliases = aliases.copy()
        else:
            col_aliases = set()
        if self.query.select:
            only_load = self.deferred_to_columns()
            for col, _ in self.query.select:
                if isinstance(col, (list, tuple)):
                    alias, column = col
                    table = self.query.alias_map[alias].table_name
                    if table in only_load and column not in only_load[table]:
                        continue
                    r = '%s.%s' % (qn(alias), qn(column))
                    if with_aliases:
                        if col[1] in col_aliases:
                            c_alias = 'Col%d' % len(col_aliases)
                            result.append('%s AS %s' % (r, c_alias))
                            aliases.add(c_alias)
                            col_aliases.add(c_alias)
                        else:
                            result.append('%s AS %s' % (r, qn2(col[1])))
                            aliases.add(r)
                            col_aliases.add(col[1])
                    else:
                        result.append(r)
                        aliases.add(r)
                        col_aliases.add(col[1])
                else:
                    col_sql, col_params = col.as_sql(qn, self.connection)
                    result.append(col_sql)
                    params.extend(col_params)

                    if hasattr(col, 'alias'):
                        aliases.add(col.alias)
                        col_aliases.add(col.alias)

        elif self.query.default_cols:
            cols, new_aliases = self.get_default_columns(with_aliases,
                    col_aliases)
            result.extend(cols)
            aliases.update(new_aliases)

        max_name_length = self.connection.ops.max_name_length()
        for alias, aggregate in self.query.aggregate_select.items():
            agg_sql, agg_params = aggregate.as_sql(qn, self.connection)
            if alias is None:
                result.append(agg_sql)
            else:
                result.append('%s AS %s' % (agg_sql, qn(truncate_name(alias, max_name_length))))
            params.extend(agg_params)

        for (table, col), _ in self.query.related_select_cols:
            r = '%s.%s' % (qn(table), qn(col))
            if with_aliases and col in col_aliases:
                c_alias = 'Col%d' % len(col_aliases)
                result.append('%s AS %s' % (r, c_alias))
                aliases.add(c_alias)
                col_aliases.add(c_alias)
            else:
                result.append(r)
                aliases.add(r)
                col_aliases.add(col)

        self._select_aliases = aliases
        return result, params
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/Django-1.6.10/django/db/models/sql/compiler.py/SQLCompiler.get_columns/operator `%` -> `-`