summaryrefslogtreecommitdiff
path: root/sql/item_buff.cc
blob: 0ac4edb3656ec310c3a6ffb7b542f6e8edc363b7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
/* 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)
{
  if (item->real_item()->type() == Item::FIELD_ITEM &&
      !(((Item_field *) (item->real_item()))->field->flags & BLOB_FLAG))
    return new Cached_item_field((Item_field *) (item->real_item()));
  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:
    DBUG_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_max_length(min(arg->max_length, thd->variables.max_sort_length)),
   value(value_max_length)
{}

bool Cached_item_str::cmp(void)
{
  String *res;
  bool tmp;

  if ((res=item->val_str(&tmp_value)))
    res->length(min(res->length(), value_max_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)
{
  longlong 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