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
|
/* Copyright (C) 2005 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; either version 2 of the License, or
(at your option) any later version.
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 */
#ifndef TABLE_MAPPING_H
#define TABLE_MAPPING_H
/* Forward declarations */
struct st_table;
typedef st_table TABLE;
/*
CLASS table_mapping
RESPONSIBILITIES
The table mapping is used to map table id's to table pointers
COLLABORATION
RELAY_LOG For mapping table id:s to tables when receiving events.
*/
/*
Guilhem to Mats:
in the table_mapping class, the memory is allocated and never freed (until
destruction). So this is a good candidate for allocating inside a MEM_ROOT:
it gives the efficient allocation in chunks (like in expand()). So I have
introduced a MEM_ROOT.
Note that inheriting from Sql_alloc had no effect: it has effects only when
"ptr= new table_mapping" is called, and this is never called. And it would
then allocate from thd->mem_root which is a highly volatile object (reset
from example after executing each query, see dispatch_command(), it has a
free_root() at end); as the table_mapping object is supposed to live longer
than a query, it was dangerous.
A dedicated MEM_ROOT needs to be used, see below.
*/
class table_mapping {
private:
MEM_ROOT m_mem_root;
public:
enum {
NO_TABLE = ULONG_MAX
};
enum enum_error {
ERR_NO_ERROR = 0,
ERR_LIMIT_EXCEEDED,
ERR_MEMORY_ALLOCATION
};
table_mapping();
~table_mapping();
TABLE* get_table(ulong table_id);
int set_table(ulong table_id, TABLE* table);
int remove_table(ulong table_id);
void clear_tables();
ulong count() const { return m_table_ids.records; }
private:
/*
This is a POD (Plain Old Data). Keep it that way (we apply offsetof() to
it, which only works for PODs)
*/
struct entry {
ulong table_id;
union {
TABLE *table;
entry *next;
};
};
entry *find_entry(ulong table_id)
{
return (entry *)hash_search(&m_table_ids,
(byte*)&table_id,
sizeof(table_id));
}
int expand();
/*
Head of the list of free entries; "free" in the sense that it's an
allocated entry free for use, NOT in the sense that it's freed
memory.
*/
entry *m_free;
/* Correspondance between an id (a number) and a TABLE object */
HASH m_table_ids;
};
#endif
|
