Drizzled Public API Documentation

cache.h
1 /* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
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3  *
4  * Copyright (C) 2008 Sun Microsystems, Inc.
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6  * This program is free software; you can redistribute it and/or modify
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8  * the Free Software Foundation; version 2 of the License.
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10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program; if not, write to the Free Software
17  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18  */
19 
20 #pragma once
21 
22 #include <drizzled/item/basic_constant.h>
23 #include <drizzled/item/field.h>
24 #include <drizzled/item/ident.h>
25 #include <drizzled/type/decimal.h>
26 #include <drizzled/util/test.h>
27 
28 namespace drizzled {
29 
31 {
32 protected:
33  Item *example;
34  table_map used_table_map;
35  /*
36  Field that this object will get value from. This is set/used by
37  index-based subquery engines to detect and remove the equality injected
38  by IN->EXISTS transformation.
39  For all other uses of Item_cache, cached_field doesn't matter.
40  */
41  Field *cached_field;
42  enum enum_field_types cached_field_type;
43 public:
44  Item_cache():
45  example(0), used_table_map(0), cached_field(0), cached_field_type(DRIZZLE_TYPE_VARCHAR)
46  {
47  fixed= 1;
48  null_value= 1;
49  }
50  Item_cache(enum_field_types field_type_arg):
51  example(0), used_table_map(0), cached_field(0), cached_field_type(field_type_arg)
52  {
53  fixed= 1;
54  null_value= 1;
55  }
56 
57  void set_used_tables(table_map map) { used_table_map= map; }
58 
59  virtual void allocate(uint32_t) {};
60  virtual bool setup(Item *item)
61  {
62  example= item;
63  max_length= item->max_length;
64  decimals= item->decimals;
65  collation.set(item->collation);
66  unsigned_flag= item->unsigned_flag;
67  if (item->type() == FIELD_ITEM)
68  cached_field= ((Item_field *)item)->field;
69  return 0;
70  };
71  virtual void store(Item *)= 0;
72  enum Type type() const { return CACHE_ITEM; }
73  enum_field_types field_type() const { return cached_field_type; }
74  static Item_cache* get_cache(const Item *item);
75  table_map used_tables() const { return used_table_map; }
76  virtual void keep_array() {}
77  virtual void print(String *str);
78  bool eq_def(Field *field);
79  bool eq(const Item *item, bool) const
80  {
81  return this == item;
82  }
83  bool basic_const_item() const
84  {
85  return test(example && example->basic_const_item());
86  }
87 };
88 
89 } /* namespace drizzled */
90