~drizzle-trunk/drizzle/development

/* Copyright (C) 2000-2006 MySQL AB

   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/**

  @file

  @brief

  Buffers to save and compare item values

*/

#include "mysql_priv.h"

/**

  Create right type of Cached_item for an item.

*/

Cached_item *new_Cached_item(THD *thd, Item *item, bool use_result_field)

{

  if (item->real_item()->type() == Item::FIELD_ITEM &&

      !(((Item_field *) (item->real_item()))->field->flags & BLOB_FLAG))

  {

    Item_field *real_item= (Item_field *) item->real_item();

    Field *cached_field= use_result_field ? real_item->result_field :

                                            real_item->field;

    return new Cached_item_field(cached_field);

  }

  switch (item->result_type()) {

  case STRING_RESULT:

    return new Cached_item_str(thd, (Item_field *) item);

  case INT_RESULT:

    return new Cached_item_int((Item_field *) item);

  case REAL_RESULT:

    return new Cached_item_real(item);

  case DECIMAL_RESULT:

    return new Cached_item_decimal(item);

  case ROW_RESULT:

  default:

    assert(0);

    return 0;

  }

}

Cached_item::~Cached_item() {}

/**

  Compare with old value and replace value with new value.

  @return

    Return true if values have changed

*/

Cached_item_str::Cached_item_str(THD *thd, Item *arg)

  :item(arg), value(min(arg->max_length, thd->variables.max_sort_length))

{}

bool Cached_item_str::cmp(void)

{

  String *res;

  bool tmp;

  if ((res=item->val_str(&tmp_value)))

    res->length(min(res->length(), value.alloced_length()));

  if (null_value != item->null_value)

  {

    if ((null_value= item->null_value))

      return(true);			// New value was null

    tmp=true;

  }

  else if (null_value)

    return(0);				// new and old value was null

  else

    tmp= sortcmp(&value,res,item->collation.collation) != 0;

  if (tmp)

    value.copy(*res);				// Remember for next cmp

  return(tmp);

}

Cached_item_str::~Cached_item_str()

{

  item=0;					// Safety

}

bool Cached_item_real::cmp(void)

{

  double nr= item->val_real();

  if (null_value != item->null_value || nr != value)

  {

    null_value= item->null_value;

    value=nr;

    return(true);

  }

  return(false);

}

bool Cached_item_int::cmp(void)

{

  int64_t nr=item->val_int();

  if (null_value != item->null_value || nr != value)

  {

    null_value= item->null_value;

    value=nr;

    return(true);

  }

  return(false);

}

bool Cached_item_field::cmp(void)

{

  bool tmp= field->cmp(buff) != 0;		// This is not a blob!

  if (tmp)

    field->get_image(buff,length,field->charset());

  if (null_value != field->is_null())

  {

    null_value= !null_value;

    tmp=true;

  }

  return(tmp);

}

Cached_item_decimal::Cached_item_decimal(Item *it)

  :item(it)

{

  my_decimal_set_zero(&value);

}

bool Cached_item_decimal::cmp()

{

  my_decimal tmp;

  my_decimal *ptmp= item->val_decimal(&tmp);

  if (null_value != item->null_value ||

      (!item->null_value && my_decimal_cmp(&value, ptmp)))

  {

    null_value= item->null_value;

    /* Save only not null values */

    if (!null_value)

    {

      my_decimal2decimal(ptmp, &value);

      return true;

    }

    return false;

  }

  return false;

}

/*****************************************************************************

** Instansiate templates

*****************************************************************************/

#ifdef HAVE_EXPLICIT_TEMPLATE_INSTANTIATION

template class List<Cached_item>;

template class List_iterator<Cached_item>;

#endif