~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, Inc.

 *

 *  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_ITEM_CACHE_H

#define DRIZZLED_ITEM_CACHE_H

#include <drizzled/item/basic_constant.h>

#include <drizzled/item/field.h>

#include <drizzled/item/ident.h>

#include <drizzled/type/decimal.h>

#include <drizzled/util/test.h>

namespace drizzled

{

class Item_cache: public Item_basic_constant

{

protected:

  Item *example;

  table_map used_table_map;

  /*

    Field that this object will get value from. This is set/used by

    index-based subquery engines to detect and remove the equality injected

    by IN->EXISTS transformation.

    For all other uses of Item_cache, cached_field doesn't matter.

  */

  Field *cached_field;

  enum enum_field_types cached_field_type;

public:

  Item_cache():

    example(0), used_table_map(0), cached_field(0), cached_field_type(DRIZZLE_TYPE_VARCHAR)

  {

    fixed= 1;

    null_value= 1;

  }

  Item_cache(enum_field_types field_type_arg):

    example(0), used_table_map(0), cached_field(0), cached_field_type(field_type_arg)

  {

    fixed= 1;

    null_value= 1;

  }

  void set_used_tables(table_map map) { used_table_map= map; }

  virtual bool allocate(uint32_t)

  { return 0; }

  virtual bool setup(Item *item)

  {

    example= item;

    max_length= item->max_length;

    decimals= item->decimals;

    collation.set(item->collation);

    unsigned_flag= item->unsigned_flag;

    if (item->type() == FIELD_ITEM)

      cached_field= ((Item_field *)item)->field;

    return 0;

  };

  virtual void store(Item *)= 0;

  enum Type type() const { return CACHE_ITEM; }

  enum_field_types field_type() const { return cached_field_type; }

  static Item_cache* get_cache(const Item *item);

  table_map used_tables() const { return used_table_map; }

  virtual void keep_array() {}

  virtual void print(String *str);

  bool eq_def(Field *field);

  bool eq(const Item *item, bool) const

  {

    return this == item;

  }

  bool basic_const_item() const

  {

    return test(example && example->basic_const_item());

  }

};

} /* namespace drizzled */

#endif /* DRIZZLED_ITEM_CACHE_H */