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
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
|
/*****************************************************************************
Copyright (c) 1997, 2016, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2018, MariaDB Corporation.
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 Street, Suite 500, Boston, MA 02110-1335 USA
*****************************************************************************/
/**************************************************//**
@file include/read0types.h
Cursor read
Created 2/16/1997 Heikki Tuuri
*******************************************************/
#ifndef read0types_h
#define read0types_h
#include <algorithm>
#include "dict0mem.h"
#include "trx0types.h"
// Friend declaration
class MVCC;
/** Read view lists the trx ids of those transactions for which a consistent
read should not see the modifications to the database. */
class ReadView {
public:
ReadView() : m_creator_trx_id(TRX_ID_MAX), m_ids(),
m_registered(false) {}
/** Check whether transaction id is valid.
@param[in] id transaction id to check
@param[in] name table name */
static void check_trx_id_sanity(
trx_id_t id,
const table_name_t& name);
/** Check whether the changes by id are visible.
@param[in] id transaction id to check against the view
@param[in] name table name
@return whether the view sees the modifications of id. */
bool changes_visible(
trx_id_t id,
const table_name_t& name) const
MY_ATTRIBUTE((warn_unused_result))
{
if (id < m_up_limit_id || id == m_creator_trx_id) {
return(true);
}
check_trx_id_sanity(id, name);
if (id >= m_low_limit_id) {
return(false);
} else if (m_ids.empty()) {
return(true);
}
return(!std::binary_search(m_ids.begin(), m_ids.end(), id));
}
/**
@param id transaction to check
@return true if view sees transaction id */
bool sees(trx_id_t id) const
{
return(id < m_up_limit_id);
}
/**
Mark the view as closed */
void close()
{
set_creator_trx_id(TRX_ID_MAX);
}
bool is_open() const
{
return static_cast<trx_id_t>(my_atomic_load64_explicit(
const_cast<int64*>(
reinterpret_cast<const int64*>(
&m_creator_trx_id)),
MY_MEMORY_ORDER_RELAXED)) != TRX_ID_MAX;
}
bool is_registered() const { return(m_registered); }
void set_registered(bool registered) { m_registered= registered; }
/**
Write the limits to the file.
@param file file to write to */
void print_limits(FILE* file) const
{
fprintf(file,
"Trx read view will not see trx with"
" id >= " TRX_ID_FMT ", sees < " TRX_ID_FMT "\n",
m_low_limit_id, m_up_limit_id);
}
/**
@return the low limit no */
trx_id_t low_limit_no() const
{
return(m_low_limit_no);
}
/**
@return the low limit id */
trx_id_t low_limit_id() const
{
return(m_low_limit_id);
}
/**
@return true if there are no transaction ids in the snapshot */
bool empty() const
{
return(m_ids.empty());
}
/**
Set the creator transaction id, existing id must be 0.
Note: This shouldbe set only for views created by RW
transactions. */
void set_creator_trx_id(trx_id_t id)
{
my_atomic_store64_explicit(
reinterpret_cast<int64*>(&m_creator_trx_id),
id, MY_MEMORY_ORDER_RELAXED);
}
#ifdef UNIV_DEBUG
/**
@param rhs view to compare with
@return truen if this view is less than or equal rhs */
bool le(const ReadView* rhs) const
{
return(m_low_limit_no <= rhs->m_low_limit_no);
}
trx_id_t up_limit_id() const
{
return(m_up_limit_id);
}
#endif /* UNIV_DEBUG */
private:
/**
Opens a read view where exactly the transactions serialized before this
point in time are seen in the view. */
inline void clone();
/**
Copy state from another view.
@param other view to copy from */
inline void copy(const ReadView& other);
friend class MVCC;
/** The read should not see any transaction with trx id >= this
value. In other words, this is the "high water mark". */
trx_id_t m_low_limit_id;
/** The read should see all trx ids which are strictly
smaller (<) than this value. In other words, this is the
low water mark". */
trx_id_t m_up_limit_id;
/** trx id of creating transaction, set to TRX_ID_MAX for free
views. */
trx_id_t m_creator_trx_id;
/** Set of RW transactions that was active when this snapshot
was taken */
trx_ids_t m_ids;
/** The view does not need to see the undo logs for transactions
whose transaction number is strictly smaller (<) than this value:
they can be removed in purge if not needed by other views */
trx_id_t m_low_limit_no;
/** true if transaction is in MVCC::m_views. Only thread that owns
this view may access it. */
bool m_registered;
byte pad1[CACHE_LINE_SIZE];
UT_LIST_NODE_T(ReadView) m_view_list;
};
#endif
|
