~drizzle-trunk/drizzle/development

/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-

 *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:

 *

 *  Copyright (C) 2008 Sun Microsystems

 *

 *  This program is free software; you can redistribute it and/or modify

 *  it under the terms of the GNU General Public License as published by

 *  the Free Software Foundation; version 2 of the License.

 *

 *  This program is distributed in the hope that it will be useful,

 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *  GNU General Public License for more details.

 *

 *  You should have received a copy of the GNU General Public License

 *  along with this program; if not, write to the Free Software

 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

 */

#ifndef DRIZZLED_FIELD_ITERATOR_H

#define DRIZZLED_FIELD_ITERATOR_H

class Table;

class TableList;

/*

  Iterator over the fields of a generic table reference.

*/

class Field_iterator: public Sql_alloc

{

public:

  Field_iterator() {}                         /* Remove gcc warning */

  virtual ~Field_iterator() {}

  virtual void set(TableList *)= 0;

  virtual void next()= 0;

  virtual bool end_of_fields()= 0;              /* Return 1 at end of list */

  virtual const char *name()= 0;

  virtual Item *create_item(THD *)= 0;

  virtual Field *field()= 0;

};

/* 

  Iterator over the fields of a base table, view with temporary

  table, or subquery.

*/

class Field_iterator_table: public Field_iterator

{

  Field **ptr;

public:

  Field_iterator_table() :ptr(0) {}

  void set(TableList *table);

  void set_table(Table *table);

  void next() { ptr++; }

  bool end_of_fields() { return *ptr == 0; }

  const char *name();

  Item *create_item(THD *thd);

  Field *field() { return *ptr; }

};

/* Iterator over the fields of a merge view. */

/*

  Field_iterator interface to the list of materialized fields of a

  NATURAL/USING join.

*/

class Field_iterator_natural_join: public Field_iterator

{

  List_iterator_fast<Natural_join_column> column_ref_it;

  Natural_join_column *cur_column_ref;

public:

  Field_iterator_natural_join() :cur_column_ref(NULL) {}

  ~Field_iterator_natural_join() {}

  void set(TableList *table);

  void next();

  bool end_of_fields() { return !cur_column_ref; }

  const char *name() { return cur_column_ref->name(); }

  Item *create_item(THD *thd) { return cur_column_ref->create_item(thd); }

  Field *field() { return cur_column_ref->field(); }

  Natural_join_column *column_ref() { return cur_column_ref; }

};

/*

  Generic iterator over the fields of an arbitrary table reference.

  DESCRIPTION

    This class unifies the various ways of iterating over the columns

    of a table reference depending on the type of SQL entity it

    represents. If such an entity represents a nested table reference,

    this iterator encapsulates the iteration over the columns of the

    members of the table reference.

  IMPLEMENTATION

    The implementation assumes that all underlying NATURAL/USING table

    references already contain their result columns and are linked into

    the list TableList::next_name_resolution_table.

*/

class Field_iterator_table_ref: public Field_iterator

{

  TableList *table_ref, *first_leaf, *last_leaf;

  Field_iterator_table        table_field_it;

  Field_iterator_natural_join natural_join_it;

  Field_iterator *field_it;

  void set_field_iterator();

public:

  Field_iterator_table_ref() :field_it(NULL) {}

  void set(TableList *table);

  void next();

  bool end_of_fields()

  { return (table_ref == last_leaf && field_it->end_of_fields()); }

  const char *name() { return field_it->name(); }

  const char *table_name();

  const char *db_name();

  Item *create_item(THD *thd) { return field_it->create_item(thd); }

  Field *field() { return field_it->field(); }

  Natural_join_column *get_or_create_column_ref(TableList *parent_table_ref);

  Natural_join_column *get_natural_column_ref();

};

#endif /* DRIZZLED_FIELD_ITERATOR_H */