MySQL 8.0.30
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rpl_transaction_write_set_ctx.h
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22
23#ifndef RPL_TRANSACTION_WRITE_SET_CTX_H
24#define RPL_TRANSACTION_WRITE_SET_CTX_H
25
26#include <stddef.h>
27#include <atomic>
28#include <list>
29#include <map>
30#include <string>
31#include <vector>
32
33#include "my_inttypes.h"
34
35/**
36 Thread class responsible for the collection of write sets associated
37 to a transaction.
38
39 It also includes support for save points where information will be discarded
40 on rollbacks to a savepoint.
41
42 Write set and flags are reset on
43 Rpl_transaction_write_set_ctx::reset_state().
44
45 The write set collection by an executing transaction is capped to a limit.
46 The limit can be "soft" or "hard":
47 - when a writeset grows above a "soft" limit, the transaction is allowed to
48 execute and commit, but the write set is discarded, and the transaction
49 declared to not have a usable write set.
50 - when a write set grows above a "hard" limit, the transaction is forced
51 to abort and rollback.
52
53 We cannot use a soft limit for transactions that will be certified in GR,
54 since a writeset is required for correct certification. But when GR is
55 disabled, we can use a soft limit, because the writeset is only used to
56 compute transaction dependencies, and we can pessimistically mark the
57 transaction as conflicting with all other transcations when the writeset
58 is discarded.
59 A soft limit can also be used for transactions executed by the GR recovery
60 channel, since they will not be certified, and the GR applier channel,
61 since those transactions have already passed the certification stage.
62
63 For the soft limit, we use
64 - binlog_transaction_dependency_history_size.
65 Transactions bigger than that cannot be added to the writeset history
66 since they do not fit, and therefore are marked as conflicting with all
67 *subsequent* transactions anyways.
68 Therefore much of the parallelization for the transaction is already
69 destroyed, and it is unlikely that also marking it as conflicting with
70 *previous* transactions makes a significant difference.
71
72 For the hard limit, when using Group Replication, we use
73 - group_replication_transaction_size_limit.
74 Since the writeset is a subset of the transaction, and the transaction
75 is limited to this size anyways, a transaction whose writeset exceeds
76 this limit will fail anyways.
77 So failing it when generating the writeset is merely a fail-fast mechanism,
78 and it is not a restriction to apply this limit to the writeset of all
79 transactions for which the full transaction data is also subject to the limit.
80 The transactions that are subject to this limit are exactly those executed
81 when GR is enabled, except by the GR applier channel and GR recovery channel.
82
83 We expose the following interfaces so that components such as GR
84 can control the limit.
85 There is an interface to *globally*
86 disable/enable the soft limit:
87 static void set_global_require_full_write_set(bool requires_ws);
88 set/alter/remove a hard limit:
89 static void set_global_write_set_memory_size_limit(uint64 limit)
90 static void update_global_write_set_memory_size_limit(uint64 limit);
91
92 There is another interface to override the global limits for a thread:
93 void set_local_ignore_write_set_memory_limit(bool ignore_limit);
94 void set_local_allow_drop_write_set(bool allow_drop_write_set);
95
96 The local methods are used for example for Group Replication applier and
97 recovery threads as group_replication_transaction_size_limit only applies
98 to client sessions and non group replication replica threads.
99*/
101 public:
104
105 /**
106 Function to add the write set of the hash of the PKE in the std::vector
107 in the transaction_ctx object.
108
109 @param[in] hash - the uint64 type hash value of the PKE.
110
111 @return true if it can't add the write set entry, false if successful
112 */
113 bool add_write_set(uint64 hash);
114
115 /*
116 Function to get the pointer of the write set vector in the
117 transaction_ctx object.
118 */
119 std::vector<uint64> *get_write_set();
120
121 /**
122 Reset the object so it can be used for a new transaction.
123 */
124 void reset_state();
125
126 /*
127 mark transactions that include tables with no pk
128 */
130
131 /*
132 check if the transaction was marked as having missing keys.
133
134 @retval true The transaction accesses tables with no PK.
135 @retval false All tables referenced in transaction have PK.
136 */
138
139 /*
140 mark transactions that include tables referenced by foreign keys
141 */
143
144 /*
145 function to check if the transaction was marked as having missing keys.
146
147 @retval true If the transaction was marked as being referenced by a foreign
148 key
149 */
151
152 /**
153 Identifies situations where the limit for number of write set entries
154 already exceeded the configure limit.
155
156 @retval true if too many write set entries exist, false otherwise
157 */
159
160 /**
161 @returns the size of the write_set field in bytes
162 */
163 size_t write_set_memory_size();
164
165 /**
166 Function to add a new SAVEPOINT identifier in the savepoint map in the
167 transaction_ctx object.
168
169 @param[in] name - the identifier name of the SAVEPOINT.
170 */
171 void add_savepoint(char *name);
172
173 /**
174 Function to delete a SAVEPOINT identifier in the savepoint map in the
175 transaction_ctx object.
176
177 @param[in] name - the identifier name of the SAVEPOINT.
178 */
179 void del_savepoint(char *name);
180
181 /**
182 Function to delete all data added to write set and savepoint since
183 SAVEPOINT identifier was added to savepoinbt in the transaction_ctx object.
184
185 @param[in] name - the identifier name of the SAVEPOINT.
186 */
187 void rollback_to_savepoint(char *name);
188
189 /**
190 Function to push savepoint data to a list and clear the savepoint map in
191 order to create another identifier context, needed on functions ant trigger.
192 */
194
195 /**
196 Restore previous savepoint map context, called after executed trigger or
197 function.
198 */
200
201 /**
202 Adds a memory limit for write sets.
203
204 @note currently only one component can set this limit a time.
205
206 @param limit the limit to be added
207 */
209
210 /**
211 Updates the memory limit for write sets.
212
213 @note Using the value 0 disables the limit
214
215 @param limit the limit to be added
216 */
218
219 /**
220 Prevent or allow this class to discard writesets exceeding a size limit
221 If true, a transaction will never discard its write sets
222
223 @param requires_ws if who invoked the method needs or not write sets
224 */
225 static void set_global_require_full_write_set(bool requires_ws);
226
227 /**
228 Set if the thread shall ignore any configured memory limit
229 for write set collection
230
231 @param ignore_limit if the limit should be ignored
232 */
233 void set_local_ignore_write_set_memory_limit(bool ignore_limit);
234
235 /**
236 Set if the thread shall if needed discard write sets
237
238 @param allow_drop_write_set if full write sets are not critical
239 */
240 void set_local_allow_drop_write_set(bool allow_drop_write_set);
241
242 private:
243 /*
244 Clear the vector that stores the PKEs, and clear the savepoints, but do not
245 restore all the flags. Outside transaction cleanup, this is used when
246 discarding a writeset of excessive size, without aborting the transaction.
247 */
248 void clear_write_set();
249
250 std::vector<uint64> write_set;
253
254 /**
255 Contains information related to SAVEPOINTs. The key on map is the
256 identifier and the value is the size of write set when command was
257 executed.
258 */
259 std::map<std::string, size_t> savepoint;
260
261 /**
262 Create a savepoint context hierarchy to support encapsulation of
263 identifier name when function or trigger are executed.
264 */
265 std::list<std::map<std::string, size_t>> savepoint_list;
266
267 // Write set restriction variables
268
269 /** There is a component requiring write sets on transactions */
271 /** Memory size limit enforced for write set collection */
272 static std::atomic<uint64> m_global_write_set_memory_size_limit;
273
274 /**
275 If the thread should or not ignore the set limit for
276 write set collection
277 */
279 /**
280 Even if a component says all transactions require write sets,
281 this variable says this thread should discard them when they are
282 bigger than m_opt_max_history_size
283 */
285
286 /** True if the write set size is over the configure limit */
288};
289
290#endif /* RPL_TRANSACTION_WRITE_SET_CTX_H */
Thread class responsible for the collection of write sets associated to a transaction.
Definition: rpl_transaction_write_set_ctx.h:100
void reset_savepoint_list()
Function to push savepoint data to a list and clear the savepoint map in order to create another iden...
Definition: rpl_transaction_write_set_ctx.cc:307
std::vector< uint64 > write_set
Definition: rpl_transaction_write_set_ctx.h:250
bool get_has_related_foreign_keys()
Definition: rpl_transaction_write_set_ctx.cc:131
static std::atomic< bool > m_global_component_requires_write_sets
There is a component requiring write sets on transactions.
Definition: rpl_transaction_write_set_ctx.h:270
size_t write_set_memory_size()
Definition: rpl_transaction_write_set_ctx.cc:141
std::list< std::map< std::string, size_t > > savepoint_list
Create a savepoint context hierarchy to support encapsulation of identifier name when function or tri...
Definition: rpl_transaction_write_set_ctx.h:265
std::vector< uint64 > * get_write_set()
Definition: rpl_transaction_write_set_ctx.cc:97
bool add_write_set(uint64 hash)
Function to add the write set of the hash of the PKE in the std::vector in the transaction_ctx object...
Definition: rpl_transaction_write_set_ctx.cc:63
bool m_local_has_reached_write_set_limit
True if the write set size is over the configure limit.
Definition: rpl_transaction_write_set_ctx.h:287
bool m_local_allow_drop_write_set
Even if a component says all transactions require write sets, this variable says this thread should d...
Definition: rpl_transaction_write_set_ctx.h:284
static void set_global_write_set_memory_size_limit(uint64 limit)
Adds a memory limit for write sets.
Definition: rpl_transaction_write_set_ctx.cc:156
bool m_has_missing_keys
Definition: rpl_transaction_write_set_ctx.h:251
static void set_global_require_full_write_set(bool requires_ws)
Prevent or allow this class to discard writesets exceeding a size limit If true, a transaction will n...
Definition: rpl_transaction_write_set_ctx.cc:146
void rollback_to_savepoint(char *name)
Function to delete all data added to write set and savepoint since SAVEPOINT identifier was added to ...
Definition: rpl_transaction_write_set_ctx.cc:263
void set_has_related_foreign_keys()
Definition: rpl_transaction_write_set_ctx.cc:126
void set_local_ignore_write_set_memory_limit(bool ignore_limit)
Set if the thread shall ignore any configured memory limit for write set collection.
Definition: rpl_transaction_write_set_ctx.cc:177
void add_savepoint(char *name)
Function to add a new SAVEPOINT identifier in the savepoint map in the transaction_ctx object.
Definition: rpl_transaction_write_set_ctx.cc:222
void reset_state()
Reset the object so it can be used for a new transaction.
Definition: rpl_transaction_write_set_ctx.cc:102
std::map< std::string, size_t > savepoint
Contains information related to SAVEPOINTs.
Definition: rpl_transaction_write_set_ctx.h:259
void del_savepoint(char *name)
Function to delete a SAVEPOINT identifier in the savepoint map in the transaction_ctx object.
Definition: rpl_transaction_write_set_ctx.cc:251
void restore_savepoint_list()
Restore previous savepoint map context, called after executed trigger or function.
Definition: rpl_transaction_write_set_ctx.cc:314
virtual ~Rpl_transaction_write_set_ctx()=default
void set_has_missing_keys()
Definition: rpl_transaction_write_set_ctx.cc:116
static void update_global_write_set_memory_size_limit(uint64 limit)
Updates the memory limit for write sets.
Definition: rpl_transaction_write_set_ctx.cc:162
bool was_write_set_limit_reached()
Identifies situations where the limit for number of write set entries already exceeded the configure ...
Definition: rpl_transaction_write_set_ctx.cc:136
bool m_has_related_foreign_keys
Definition: rpl_transaction_write_set_ctx.h:252
void clear_write_set()
Definition: rpl_transaction_write_set_ctx.cc:109
static std::atomic< uint64 > m_global_write_set_memory_size_limit
Memory size limit enforced for write set collection.
Definition: rpl_transaction_write_set_ctx.h:272
void set_local_allow_drop_write_set(bool allow_drop_write_set)
Set if the thread shall if needed discard write sets.
Definition: rpl_transaction_write_set_ctx.cc:182
bool get_has_missing_keys()
Definition: rpl_transaction_write_set_ctx.cc:121
Rpl_transaction_write_set_ctx()
Definition: rpl_transaction_write_set_ctx.cc:47
bool m_ignore_write_set_memory_limit
If the thread should or not ignore the set limit for write set collection.
Definition: rpl_transaction_write_set_ctx.h:278
Some integer typedefs for easier portability.
uint64_t uint64
Definition: my_inttypes.h:68
case opt name
Definition: sslopt-case.h:32