summaryrefslogtreecommitdiff
path: root/sql/session_tracker.cc
blob: 5188891398379547035905c496052157c1704085 (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
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
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
/* Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
   Copyright (c) 2016, MariaDB

   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 St, Fifth Floor, Boston, MA 02110-1301  USA */


#ifndef EMBEDDED_LIBRARY
#include "sql_plugin.h"
#include "session_tracker.h"

#include "hash.h"
#include "table.h"
#include "rpl_gtid.h"
#include "sql_class.h"
#include "sql_show.h"
#include "sql_plugin.h"
#include "set_var.h"

void State_tracker::mark_as_changed(THD *thd, LEX_CSTRING *tracked_item_name)
{
  m_changed= true;
  thd->lex->safe_to_cache_query= 0;
  thd->server_status|= SERVER_SESSION_STATE_CHANGED;
}


class Not_implemented_tracker : public State_tracker
{
public:
  bool enable(THD *thd)
  { return false; }
  bool update(THD *, set_var *)
  { return false; }
  bool store(THD *, String *)
  { return false; }
  void mark_as_changed(THD *, LEX_CSTRING *tracked_item_name)
  {}

};

/**
  Session_sysvars_tracker

  This is a tracker class that enables & manages the tracking of session
  system variables. It internally maintains a hash of user supplied variable
  references and a boolean field to store if the variable was changed by the
  last statement.
*/

class Session_sysvars_tracker : public State_tracker
{
private:

  struct sysvar_node_st {
    sys_var *m_svar;
    bool *test_load;
    bool m_changed;
  };

  class vars_list
  {
  private:
    /**
      Registered system variables. (@@session_track_system_variables)
      A hash to store the name of all the system variables specified by the
      user.
    */
    HASH m_registered_sysvars;
    /** Size of buffer for string representation */
    size_t buffer_length;
    myf m_mem_flag;
    /**
      If TRUE then we want to check all session variable.
    */
    bool track_all;
    void init()
    {
      my_hash_init(&m_registered_sysvars,
                   &my_charset_bin,
		   4, 0, 0, (my_hash_get_key) sysvars_get_key,
		   my_free, MYF(HASH_UNIQUE |
                                ((m_mem_flag & MY_THREAD_SPECIFIC) ?
                                 HASH_THREAD_SPECIFIC : 0)));
    }
    void free_hash()
    {
      if (my_hash_inited(&m_registered_sysvars))
      {
	my_hash_free(&m_registered_sysvars);
      }
    }

    uchar* search(const sys_var *svar)
    {
      return (my_hash_search(&m_registered_sysvars, (const uchar *)&svar,
			     sizeof(sys_var *)));
    }

  public:
    vars_list() :
      buffer_length(0)
    {
      m_mem_flag= current_thd ? MY_THREAD_SPECIFIC : 0;
      init();
    }

    size_t get_buffer_length()
    {
      DBUG_ASSERT(buffer_length != 0); // asked earlier then should
      return buffer_length;
    }
    ~vars_list()
    {
      /* free the allocated hash. */
      if (my_hash_inited(&m_registered_sysvars))
      {
	my_hash_free(&m_registered_sysvars);
      }
    }

    uchar* insert_or_search(sysvar_node_st *node, const sys_var *svar)
    {
      uchar *res;
      res= search(svar);
      if (!res)
      {
	if (track_all)
	{
	  insert(node, svar, m_mem_flag);
	  return search(svar);
	}
      }
      return res;
    }

    bool insert(sysvar_node_st *node, const sys_var *svar, myf mem_flag);
    void reinit();
    void reset();
    inline bool is_enabled()
    {
      return track_all || m_registered_sysvars.records;
    }
    void copy(vars_list* from, THD *thd);
    bool parse_var_list(THD *thd, LEX_STRING var_list, bool throw_error,
                        CHARSET_INFO *char_set, bool take_mutex);
    bool construct_var_list(char *buf, size_t buf_len);
    bool store(THD *thd, String *buf);
  };
  /**
    Two objects of vars_list type are maintained to manage
    various operations.
  */
  vars_list *orig_list, *tool_list;

public:
  Session_sysvars_tracker()
  {
    orig_list= new (std::nothrow) vars_list();
    tool_list= new (std::nothrow) vars_list();
  }

  ~Session_sysvars_tracker()
  {
    if (orig_list)
      delete orig_list;
    if (tool_list)
      delete tool_list;
  }

  size_t get_buffer_length()
  {
    return orig_list->get_buffer_length();
  }
  bool construct_var_list(char *buf, size_t buf_len)
  {
    return orig_list->construct_var_list(buf, buf_len);
  }

  /**
    Method used to check the validity of string provided
    for session_track_system_variables during the server
    startup.
  */
  static bool server_init_check(THD *thd, CHARSET_INFO *char_set,
                                LEX_STRING var_list)
  {
    return check_var_list(thd, var_list, false, char_set, false);
  }

  static bool server_init_process(THD *thd, CHARSET_INFO *char_set,
                                  LEX_STRING var_list)
  {
    vars_list dummy;
    bool result;
    result= dummy.parse_var_list(thd, var_list, false, char_set, false);
    if (!result)
      dummy.construct_var_list(var_list.str, var_list.length + 1);
    return result;
  }

  void reset();
  bool enable(THD *thd);
  bool check_str(THD *thd, LEX_STRING *val);
  bool update(THD *thd, set_var *var);
  bool store(THD *thd, String *buf);
  void mark_as_changed(THD *thd, LEX_CSTRING *tracked_item_name);
  /* callback */
  static uchar *sysvars_get_key(const char *entry, size_t *length,
                                my_bool not_used __attribute__((unused)));

  // hash iterators
  static my_bool name_array_filler(void *ptr, void *data_ptr);
  static my_bool store_variable(void *ptr, void *data_ptr);
  static my_bool reset_variable(void *ptr, void *data_ptr);

  static bool check_var_list(THD *thd, LEX_STRING var_list, bool throw_error,
                             CHARSET_INFO *char_set, bool take_mutex);
};



/**
  Current_schema_tracker,

  This is a tracker class that enables & manages the tracking of current
  schema for a particular connection.
*/

class Current_schema_tracker : public State_tracker
{
private:
  bool schema_track_inited;
  void reset();

public:

  Current_schema_tracker()
  {
    schema_track_inited= false;
  }

  bool enable(THD *thd)
  { return update(thd, NULL); }
  bool update(THD *thd, set_var *var);
  bool store(THD *thd, String *buf);
};

/*
  Session_state_change_tracker

  This is a boolean tracker class that will monitor any change that contributes
  to a session state change.
  Attributes that contribute to session state change include:
     - Successful change to System variables
     - User defined variables assignments
     - temporary tables created, altered or deleted
     - prepared statements added or removed
     - change in current database
     - change of current role
*/

class Session_state_change_tracker : public State_tracker
{
private:

  void reset();

public:
  Session_state_change_tracker();
  bool enable(THD *thd)
  { return update(thd, NULL); };
  bool update(THD *thd, set_var *var);
  bool store(THD *thd, String *buf);
  bool is_state_changed(THD*);
};


/* To be used in expanding the buffer. */
static const unsigned int EXTRA_ALLOC= 1024;


void Session_sysvars_tracker::vars_list::reinit()
{
  buffer_length= 0;
  track_all= 0;
  if (m_registered_sysvars.records)
    my_hash_reset(&m_registered_sysvars);
}

/**
  Copy the given list.

  @param  from    Source vars_list object.
  @param  thd     THD handle to retrive the charset in use.

  @retval true  there is something to track
  @retval false nothing to track
*/

void Session_sysvars_tracker::vars_list::copy(vars_list* from, THD *thd)
{
  reinit();
  track_all= from->track_all;
  free_hash();
  buffer_length= from->buffer_length;
  m_registered_sysvars= from->m_registered_sysvars;
  from->init();
}

/**
  Inserts the variable to be tracked into m_registered_sysvars hash.

  @param   node   Node to be inserted.
  @param   svar   address of the system variable

  @retval false success
  @retval true  error
*/

bool Session_sysvars_tracker::vars_list::insert(sysvar_node_st *node,
                                                const sys_var *svar,
                                                myf mem_flag)
{
  if (!node)
  {
    if (!(node= (sysvar_node_st *) my_malloc(sizeof(sysvar_node_st),
                                             MYF(MY_WME | mem_flag))))
    {
      reinit();
      return true;
    }
  }

  node->m_svar= (sys_var *)svar;
  node->test_load= node->m_svar->test_load;
  node->m_changed= false;
  if (my_hash_insert(&m_registered_sysvars, (uchar *) node))
  {
    my_free(node);
    if (!search((sys_var *)svar))
    {
      //EOF (error is already reported)
      reinit();
      return true;
    }
  }
  return false;
}

/**
  Parse the specified system variables list.

  @Note In case of invalid entry a warning is raised per invalid entry.
  This is done in order to handle 'potentially' valid system
  variables from uninstalled plugins which might get installed in
  future.


  @param thd             [IN]    The thd handle.
  @param var_list        [IN]    System variable list.
  @param throw_error     [IN]    bool when set to true, returns an error
                                 in case of invalid/duplicate values.
  @param char_set	 [IN]	 charecter set information used for string
				 manipulations.
  @param take_mutex      [IN]    take LOCK_plugin

  @return
    true                    Error
    false                   Success
*/
bool Session_sysvars_tracker::vars_list::parse_var_list(THD *thd,
                                                        LEX_STRING var_list,
                                                        bool throw_error,
							CHARSET_INFO *char_set,
							bool take_mutex)
{
  const char separator= ',';
  char *token, *lasts= NULL;
  size_t rest= var_list.length;
  reinit();

  if (!var_list.str || var_list.length == 0)
  {
    buffer_length= 1;
    return false;
  }

  if(!strcmp(var_list.str, "*"))
  {
    track_all= true;
    buffer_length= 2;
    return false;
  }

  buffer_length= var_list.length + 1;
  token= var_list.str;

  track_all= false;
  /*
    If Lock to the plugin mutex is not acquired here itself, it results
    in having to acquire it multiple times in find_sys_var_ex for each
    token value. Hence the mutex is handled here to avoid a performance
    overhead.
  */
  if (!thd || take_mutex)
    mysql_mutex_lock(&LOCK_plugin);
  for (;;)
  {
    sys_var *svar;
    LEX_CSTRING var;
    uint not_used;

    lasts= (char *) memchr(token, separator, rest);

    var.str= token;
    if (lasts)
    {
      var.length= (lasts - token);
      rest-= var.length + 1;
    }
    else
      var.length= rest;

    /* Remove leading/trailing whitespace. */
    trim_whitespace(char_set, &var, &not_used);

    if(!strcmp(var.str, "*"))
    {
      track_all= true;
    }
    else if ((svar=
              find_sys_var_ex(thd, var.str, var.length, throw_error, true)))
    {
      if (insert(NULL, svar, m_mem_flag) == TRUE)
        goto error;
    }
    else if (throw_error && thd)
    {
      push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,
                          ER_WRONG_VALUE_FOR_VAR,
                          "%.*s is not a valid system variable and will"
                          "be ignored.", (int)var.length, token);
    }
    else
      goto error;

    if (lasts)
      token= lasts + 1;
    else
      break;
  }
  if (!thd || take_mutex)
    mysql_mutex_unlock(&LOCK_plugin);

  return false;

error:
  if (!thd || take_mutex)
    mysql_mutex_unlock(&LOCK_plugin);
  return true;
}


bool Session_sysvars_tracker::check_var_list(THD *thd,
                                             LEX_STRING var_list,
                                             bool throw_error,
                                             CHARSET_INFO *char_set,
                                             bool take_mutex)
{
  const char separator= ',';
  char *token, *lasts= NULL;
  size_t rest= var_list.length;

  if (!var_list.str || var_list.length == 0 ||
      !strcmp(var_list.str, "*"))
  {
    return false;
  }

  token= var_list.str;

  /*
    If Lock to the plugin mutex is not acquired here itself, it results
    in having to acquire it multiple times in find_sys_var_ex for each
    token value. Hence the mutex is handled here to avoid a performance
    overhead.
  */
  if (!thd || take_mutex)
    mysql_mutex_lock(&LOCK_plugin);
  for (;;)
  {
    LEX_CSTRING var;
    uint not_used;

    lasts= (char *) memchr(token, separator, rest);

    var.str= token;
    if (lasts)
    {
      var.length= (lasts - token);
      rest-= var.length + 1;
    }
    else
      var.length= rest;

    /* Remove leading/trailing whitespace. */
    trim_whitespace(char_set, &var, &not_used);

    if(!strcmp(var.str, "*") &&
       !find_sys_var_ex(thd, var.str, var.length, throw_error, true))
    {
      if (throw_error && take_mutex && thd)
      {
        push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,
                            ER_WRONG_VALUE_FOR_VAR,
                            "%.*s is not a valid system variable and will"
                            "be ignored.", (int)var.length, token);
      }
      else
      {
        if (!thd || take_mutex)
          mysql_mutex_unlock(&LOCK_plugin);
        return true;
      }
    }

    if (lasts)
      token= lasts + 1;
    else
      break;
  }
  if (!thd || take_mutex)
    mysql_mutex_unlock(&LOCK_plugin);

  return false;
}

struct name_array_filler_data
{
  LEX_CSTRING **names;
  uint idx;

};

/** Collects variable references into array */
my_bool Session_sysvars_tracker::name_array_filler(void *ptr,
                                                   void *data_ptr)
{
  Session_sysvars_tracker::sysvar_node_st *node=
    (Session_sysvars_tracker::sysvar_node_st *)ptr;
  name_array_filler_data *data= (struct name_array_filler_data *)data_ptr;
  if (*node->test_load)
    data->names[data->idx++]= &node->m_svar->name;
  return FALSE;
}

/* Sorts variable references array */
static int name_array_sorter(const void *a, const void *b)
{
  LEX_CSTRING **an= (LEX_CSTRING **)a, **bn=(LEX_CSTRING **)b;
  size_t min= MY_MIN((*an)->length, (*bn)->length);
  int res= strncmp((*an)->str, (*bn)->str, min);
  if (res == 0)
    res= ((int)(*bn)->length)- ((int)(*an)->length);
  return res;
}

/**
  Construct variable list by internal hash with references
*/

bool Session_sysvars_tracker::vars_list::construct_var_list(char *buf,
                                                            size_t buf_len)
{
  struct name_array_filler_data data;
  size_t left= buf_len;
  size_t names_size= m_registered_sysvars.records * sizeof(LEX_CSTRING *);
  const char separator= ',';

  if (unlikely(buf_len < 1))
    return true;

  if (unlikely(track_all))
  {
    if (buf_len < 2)
      return true;
    buf[0]= '*';
    buf[1]= '\0';
    return false;
  }

  if (m_registered_sysvars.records == 0)
  {
    buf[0]= '\0';
    return false;
  }

  data.names= (LEX_CSTRING**)my_safe_alloca(names_size);

  if (unlikely(!data.names))
    return true;

  data.idx= 0;

  mysql_mutex_lock(&LOCK_plugin);
  my_hash_iterate(&m_registered_sysvars, &name_array_filler, &data);
  DBUG_ASSERT(data.idx <= m_registered_sysvars.records);

  /*
    We check number of records again here because number of variables
    could be reduced in case of plugin unload.
  */
  if (m_registered_sysvars.records == 0)
  {
    mysql_mutex_unlock(&LOCK_plugin);
    buf[0]= '\0';
    return false;
  }

  my_qsort(data.names, data.idx, sizeof(LEX_CSTRING *),
           &name_array_sorter);

  for(uint i= 0; i < data.idx; i++)
  {
    LEX_CSTRING *nm= data.names[i];
    size_t ln= nm->length + 1;
    if (ln > left)
    {
      mysql_mutex_unlock(&LOCK_plugin);
      my_safe_afree(data.names, names_size);
      return true;
    }
    memcpy(buf, nm->str, nm->length);
    buf[nm->length]= separator;
    buf+= ln;
    left-= ln;
  }
  mysql_mutex_unlock(&LOCK_plugin);

  buf--; buf[0]= '\0';
  my_safe_afree(data.names, names_size);

  return false;
}

/**
  Enable session tracker by parsing global value of tracked variables.

  @param thd    [IN]        The thd handle.

  @retval true  Error
  @retval false Success
*/

bool Session_sysvars_tracker::enable(THD *thd)
{
  mysql_mutex_lock(&LOCK_plugin);
  LEX_STRING tmp;
  tmp.str= global_system_variables.session_track_system_variables;
  tmp.length= safe_strlen(tmp.str);
  if (tool_list->parse_var_list(thd, tmp,
                                true, thd->charset(), false) == true)
  {
    mysql_mutex_unlock(&LOCK_plugin);
    return true;
  }
  mysql_mutex_unlock(&LOCK_plugin);
  orig_list->copy(tool_list, thd);
  m_enabled= true;

  return false;
}


/**
  Check system variable name(s).

  @note This function is called from the ON_CHECK() function of the
        session_track_system_variables' sys_var class.

  @param thd    [IN]        The thd handle.
  @param var    [IN]        A pointer to set_var holding the specified list of
                            system variable names.

  @retval true  Error
  @retval false Success
*/

inline bool Session_sysvars_tracker::check_str(THD *thd, LEX_STRING *val)
{
  return Session_sysvars_tracker::check_var_list(thd, *val, true,
                                                 thd->charset(), true);
}


/**
  Once the value of the @@session_track_system_variables has been
  successfully updated, this function calls
  Session_sysvars_tracker::vars_list::copy updating the hash in orig_list
  which represents the system variables to be tracked.

  @note This function is called from the ON_UPDATE() function of the
        session_track_system_variables' sys_var class.

  @param thd    [IN]        The thd handle.

  @retval true  Error
  @retval false Success
*/

bool Session_sysvars_tracker::update(THD *thd, set_var *var)
{
  /*
    We are doing via tool list because there possible errors with memory
    in this case value will be unchanged.
  */
  tool_list->reinit();
  if (tool_list->parse_var_list(thd, var->save_result.string_value, true,
                                thd->charset(), true))
    return true;
  orig_list->copy(tool_list, thd);
  return false;
}


/*
  Function and structure to support storing variables from hash to the buffer.
*/

struct st_store_variable_param
{
  THD *thd;
  String *buf;
};

my_bool Session_sysvars_tracker::store_variable(void *ptr, void *data_ptr)
{
  Session_sysvars_tracker::sysvar_node_st *node=
    (Session_sysvars_tracker::sysvar_node_st *)ptr;
  if (node->m_changed)
  {
    THD *thd= ((st_store_variable_param *)data_ptr)->thd;
    String *buf= ((st_store_variable_param *)data_ptr)->buf;
    char val_buf[SHOW_VAR_FUNC_BUFF_SIZE];
    SHOW_VAR show;
    CHARSET_INFO *charset;
    size_t val_length, length;
    mysql_mutex_lock(&LOCK_plugin);
    if (!*node->test_load)
    {
      mysql_mutex_unlock(&LOCK_plugin);
      return false;
    }
    sys_var *svar= node->m_svar;
    bool is_plugin= svar->cast_pluginvar();
    if (!is_plugin)
      mysql_mutex_unlock(&LOCK_plugin);

    /* As its always system variable. */
    show.type= SHOW_SYS;
    show.name= svar->name.str;
    show.value= (char *) svar;

    const char *value= get_one_variable(thd, &show, OPT_SESSION, SHOW_SYS, NULL,
                                        &charset, val_buf, &val_length);
    if (is_plugin)
      mysql_mutex_unlock(&LOCK_plugin);

    length= net_length_size(svar->name.length) +
      svar->name.length +
      net_length_size(val_length) +
      val_length;

    compile_time_assert(SESSION_TRACK_SYSTEM_VARIABLES < 251);
    if (unlikely((1 + net_length_size(length) + length + buf->length() >=
                  MAX_PACKET_LENGTH) ||
                 buf->reserve(1 + net_length_size(length) + length,
                              EXTRA_ALLOC)))
      return true;


    /* Session state type (SESSION_TRACK_SYSTEM_VARIABLES) */
    buf->q_append((char)SESSION_TRACK_SYSTEM_VARIABLES);

    /* Length of the overall entity. */
    buf->q_net_store_length((ulonglong)length);

    /* System variable's name (length-encoded string). */
    buf->q_net_store_data((const uchar*)svar->name.str, svar->name.length);

    /* System variable's value (length-encoded string). */
    buf->q_net_store_data((const uchar*)value, val_length);
  }
  return false;
}

bool Session_sysvars_tracker::vars_list::store(THD *thd, String *buf)
{
  st_store_variable_param data= {thd, buf};
  return my_hash_iterate(&m_registered_sysvars, &store_variable, &data);
}

/**
  Store the data for changed system variables in the specified buffer.
  Once the data is stored, we reset the flags related to state-change
  (see reset()).

  @param thd [IN]           The thd handle.
  @paran buf [INOUT]        Buffer to store the information to.

  @retval true  Error
  @retval false Success
*/

bool Session_sysvars_tracker::store(THD *thd, String *buf)
{
  if (!orig_list->is_enabled())
    return false;

  if (orig_list->store(thd, buf))
    return true;

  reset();

  return false;
}


/**
  Mark the system variable as changed.

  @param               [IN] pointer on a variable
*/

void Session_sysvars_tracker::mark_as_changed(THD *thd,
                                              LEX_CSTRING *var)
{
  sysvar_node_st *node= NULL;
  sys_var *svar= (sys_var *)var;
  /*
    Check if the specified system variable is being tracked, if so
    mark it as changed and also set the class's m_changed flag.
  */
  if (orig_list->is_enabled() &&
      (node= (sysvar_node_st *) (orig_list->insert_or_search(node, svar))))
  {
    node->m_changed= true;
    State_tracker::mark_as_changed(thd, var);
  }
}


/**
  Supply key to a hash.

  @param entry  [IN]        A single entry.
  @param length [OUT]       Length of the key.
  @param not_used           Unused.

  @return Pointer to the key buffer.
*/

uchar *Session_sysvars_tracker::sysvars_get_key(const char *entry,
                                                size_t *length,
                                                my_bool not_used __attribute__((unused)))
{
  *length= sizeof(sys_var *);
  return (uchar *) &(((sysvar_node_st *) entry)->m_svar);
}


/* Function to support resetting hash nodes for the variables */

my_bool Session_sysvars_tracker::reset_variable(void *ptr,
                                                   void *data_ptr)
{
  ((Session_sysvars_tracker::sysvar_node_st *)ptr)->m_changed= false;
  return false;
}

void Session_sysvars_tracker::vars_list::reset()
{
  my_hash_iterate(&m_registered_sysvars, &reset_variable, NULL);
}

/**
  Prepare/reset the m_registered_sysvars hash for next statement.
*/

void Session_sysvars_tracker::reset()
{

  orig_list->reset();
  m_changed= false;
}

static Session_sysvars_tracker* sysvar_tracker(THD *thd)
{
  return (Session_sysvars_tracker*)
    thd->session_tracker.get_tracker(SESSION_SYSVARS_TRACKER);
}

bool sysvartrack_validate_value(THD *thd, const char *str, size_t len)
{
  LEX_STRING tmp= {(char *)str, len};
  return Session_sysvars_tracker::server_init_check(thd, system_charset_info,
                                                    tmp);
}
bool sysvartrack_reprint_value(THD *thd, char *str, size_t len)
{
  LEX_STRING tmp= {str, len};
  return Session_sysvars_tracker::server_init_process(thd,
                                                       system_charset_info,
                                                       tmp);
}
bool sysvartrack_update(THD *thd, set_var *var)
{
  return sysvar_tracker(thd)->update(thd, var);
}
size_t sysvartrack_value_len(THD *thd)
{
  return sysvar_tracker(thd)->get_buffer_length();
}
bool sysvartrack_value_construct(THD *thd, char *val, size_t len)
{
  return sysvar_tracker(thd)->construct_var_list(val, len);
}

///////////////////////////////////////////////////////////////////////////////

/**
  Enable/disable the tracker based on @@session_track_schema's value.

  @param thd [IN]           The thd handle.

  @return
    false (always)
*/

bool Current_schema_tracker::update(THD *thd, set_var *)
{
  m_enabled= thd->variables.session_track_schema;
  return false;
}


/**
  Store the schema name as length-encoded string in the specified buffer.

  @param thd [IN]           The thd handle.
  @paran buf [INOUT]        Buffer to store the information to.

  @reval  false Success
  @retval true  Error
*/

bool Current_schema_tracker::store(THD *thd, String *buf)
{
  size_t db_length, length;

  /*
    Protocol made (by unknown reasons) redundant:
    It saves length of database name and name of database name +
    length of saved length of database length.
  */
  length= db_length= thd->db.length;
  length += net_length_size(length);

  compile_time_assert(SESSION_TRACK_SCHEMA < 251);
  compile_time_assert(NAME_LEN < 251);
  DBUG_ASSERT(length < 251);
  if (unlikely((1 + 1 + length + buf->length() >= MAX_PACKET_LENGTH) ||
               buf->reserve(1 + 1 + length, EXTRA_ALLOC)))
    return true;

  /* Session state type (SESSION_TRACK_SCHEMA) */
  buf->q_append((char)SESSION_TRACK_SCHEMA);

  /* Length of the overall entity. */
  buf->q_net_store_length(length);

  /* Length and current schema name */
  buf->q_net_store_data((const uchar *)thd->db.str, thd->db.length);

  reset();

  return false;
}


/**
  Reset the m_changed flag for next statement.

  @return                   void
*/

void Current_schema_tracker::reset()
{
  m_changed= false;
}


///////////////////////////////////////////////////////////////////////////////


Transaction_state_tracker::Transaction_state_tracker()
{
  m_enabled        = false;
  tx_changed       = TX_CHG_NONE;
  tx_curr_state    =
  tx_reported_state= TX_EMPTY;
  tx_read_flags    = TX_READ_INHERIT;
  tx_isol_level    = TX_ISOL_INHERIT;
}

/**
  Enable/disable the tracker based on @@session_track_transaction_info.

  @param thd [IN]           The thd handle.

  @retval true if updating the tracking level failed
  @retval false otherwise
*/

bool Transaction_state_tracker::update(THD *thd, set_var *)
{
  if (thd->variables.session_track_transaction_info != TX_TRACK_NONE)
  {
    /*
      If we only just turned reporting on (rather than changing between
      state and characteristics reporting), start from a defined state.
    */
    if (!m_enabled)
    {
      tx_curr_state     =
      tx_reported_state = TX_EMPTY;
      tx_changed       |= TX_CHG_STATE;
      m_enabled= true;
    }
    if (thd->variables.session_track_transaction_info == TX_TRACK_CHISTICS)
      tx_changed       |= TX_CHG_CHISTICS;
    mark_as_changed(thd, NULL);
  }
  else
    m_enabled= false;

  return false;
}


/**
  Store the transaction state (and, optionally, characteristics)
  as length-encoded string in the specified buffer.  Once the data
  is stored, we reset the flags related to state-change (see reset()).


  @param thd [IN]           The thd handle.
  @paran buf [INOUT]        Buffer to store the information to.

  @retval false Success
  @retval true  Error
*/

static LEX_CSTRING isol[]= {
  { STRING_WITH_LEN("READ UNCOMMITTED") },
  { STRING_WITH_LEN("READ COMMITTED") },
  { STRING_WITH_LEN("REPEATABLE READ") },
  { STRING_WITH_LEN("SERIALIZABLE") }
};

bool Transaction_state_tracker::store(THD *thd, String *buf)
{
  /* STATE */
  if (tx_changed & TX_CHG_STATE)
  {
    if (unlikely((11 + buf->length() >= MAX_PACKET_LENGTH) ||
                 buf->reserve(11, EXTRA_ALLOC)))
      return true;

    buf->q_append((char)SESSION_TRACK_TRANSACTION_STATE);

    buf->q_append((char)9); // whole packet length
    buf->q_append((char)8); // results length

    buf->q_append((char)((tx_curr_state & TX_EXPLICIT)        ? 'T' :
                         ((tx_curr_state & TX_IMPLICIT)       ? 'I' : '_')));
    buf->q_append((char)((tx_curr_state & TX_READ_UNSAFE)     ? 'r' : '_'));
    buf->q_append((char)(((tx_curr_state & TX_READ_TRX) ||
                          (tx_curr_state & TX_WITH_SNAPSHOT)) ? 'R' : '_'));
    buf->q_append((char)((tx_curr_state & TX_WRITE_UNSAFE)   ? 'w' : '_'));
    buf->q_append((char)((tx_curr_state & TX_WRITE_TRX)      ? 'W' : '_'));
    buf->q_append((char)((tx_curr_state & TX_STMT_UNSAFE)    ? 's' : '_'));
    buf->q_append((char)((tx_curr_state & TX_RESULT_SET)     ? 'S' : '_'));
    buf->q_append((char)((tx_curr_state & TX_LOCKED_TABLES)  ? 'L' : '_'));
  }

  /* CHARACTERISTICS -- How to restart the transaction */

  if ((thd->variables.session_track_transaction_info == TX_TRACK_CHISTICS) &&
      (tx_changed & TX_CHG_CHISTICS))
  {
    bool is_xa= (thd->transaction.xid_state.xa_state != XA_NOTR);
    size_t start;

    /* 2 length by 1 byte and code */
    if (unlikely((1 + 1 + 1 + 110 + buf->length() >= MAX_PACKET_LENGTH) ||
                 buf->reserve(1 + 1 + 1, EXTRA_ALLOC)))
      return true;

    compile_time_assert(SESSION_TRACK_TRANSACTION_CHARACTERISTICS < 251);
    /* Session state type (SESSION_TRACK_TRANSACTION_CHARACTERISTICS) */
    buf->q_append((char)SESSION_TRACK_TRANSACTION_CHARACTERISTICS);

    /* placeholders for lengths. will be filled in at the end */
    buf->q_append('\0');
    buf->q_append('\0');

    start= buf->length();

    {
      /*
        We have four basic replay scenarios:

        a) SET TRANSACTION was used, but before an actual transaction
           was started, the load balancer moves the connection elsewhere.
           In that case, the same one-shots should be set up in the
           target session.  (read-only/read-write; isolation-level)

        b) The initial transaction has begun; the relevant characteristics
           are the session defaults, possibly overridden by previous
           SET TRANSACTION statements, possibly overridden or extended
           by options passed to the START TRANSACTION statement.
           If the load balancer wishes to move this transaction,
           it needs to be replayed with the correct characteristics.
           (read-only/read-write from SET or START;
           isolation-level from SET only, snapshot from START only)

        c) A subsequent transaction started with START TRANSACTION
           (which is legal syntax in lieu of COMMIT AND CHAIN in MySQL)
           may add/modify the current one-shots:

           - It may set up a read-only/read-write one-shot.
             This one-shot will override the value used in the previous
             transaction (whether that came from the default or a one-shot),
             and, like all one-shots currently do, it will carry over into
             any subsequent transactions that don't explicitly override them
             in turn. This behavior is not guaranteed in the docs and may
             change in the future, but the tracker item should correctly
             reflect whatever behavior a given version of mysqld implements.

           - It may also set up a WITH CONSISTENT SNAPSHOT one-shot.
             This one-shot does not currently carry over into subsequent
             transactions (meaning that with "traditional syntax", WITH
             CONSISTENT SNAPSHOT can only be requested for the first part
             of a transaction chain). Again, the tracker item should reflect
             mysqld behavior.

        d) A subsequent transaction started using COMMIT AND CHAIN
           (or, for that matter, BEGIN WORK, which is currently
           legal and equivalent syntax in MySQL, or START TRANSACTION
           sans options) will re-use any one-shots set up so far
           (with SET before the first transaction started, and with
           all subsequent STARTs), except for WITH CONSISTANT SNAPSHOT,
           which will never be chained and only applies when explicitly
           given.

        It bears noting that if we switch sessions in a follow-up
        transaction, SET TRANSACTION would be illegal in the old
        session (as a transaction is active), whereas in the target
        session which is being prepared, it should be legal, as no
        transaction (chain) should have started yet.

        Therefore, we are free to generate SET TRANSACTION as a replay
        statement even for a transaction that isn't the first in an
        ongoing chain. Consider

          SET TRANSACTION ISOLATION LEVEL READ UNCOMMITED;
          START TRANSACTION READ ONLY, WITH CONSISTENT SNAPSHOT;
          # work
          COMMIT AND CHAIN;

        If we switch away at this point, the replay in the new session
        needs to be

          SET TRANSACTION ISOLATION LEVEL READ UNCOMMITED;
          START TRANSACTION READ ONLY;

        When a transaction ends (COMMIT/ROLLBACK sans CHAIN), all
        per-transaction characteristics are reset to the session's
        defaults.

        This also holds for a transaction ended implicitly!  (transaction.cc)
        Once again, the aim is to have the tracker item reflect on a
        given mysqld's actual behavior.
      */

      /*
        "ISOLATION LEVEL"
        Only legal in SET TRANSACTION, so will always be replayed as such.
      */
      if (tx_isol_level != TX_ISOL_INHERIT)
      {
        /*
          Unfortunately, we can't re-use tx_isolation_names /
          tx_isolation_typelib as it hyphenates its items.
        */
        buf->append(STRING_WITH_LEN("SET TRANSACTION ISOLATION LEVEL "));
        buf->append(&isol[tx_isol_level - 1]);
        buf->append(STRING_WITH_LEN("; "));
      }

      /*
        Start transaction will usually result in TX_EXPLICIT (transaction
        started, but no data attached yet), except when WITH CONSISTENT
        SNAPSHOT, in which case we may have data pending.
        If it's an XA transaction, we don't go through here so we can
        first print the trx access mode ("SET TRANSACTION READ ...")
        separately before adding XA START (whereas with START TRANSACTION,
        we can merge the access mode into the same statement).
      */
      if ((tx_curr_state & TX_EXPLICIT) && !is_xa)
      {
        buf->append(STRING_WITH_LEN("START TRANSACTION"));

        /*
          "WITH CONSISTENT SNAPSHOT"
          Defaults to no, can only be enabled.
          Only appears in START TRANSACTION.
        */
        if (tx_curr_state & TX_WITH_SNAPSHOT)
        {
          buf->append(STRING_WITH_LEN(" WITH CONSISTENT SNAPSHOT"));
          if (tx_read_flags != TX_READ_INHERIT)
            buf->append(STRING_WITH_LEN(","));
        }

        /*
          "READ WRITE / READ ONLY" can be set globally, per-session,
          or just for one transaction.

          The latter case can take the form of
          START TRANSACTION READ (WRITE|ONLY), or of
          SET TRANSACTION READ (ONLY|WRITE).
          (Both set thd->read_only for the upcoming transaction;
          it will ultimately be re-set to the session default.)

          As the regular session-variable tracker does not monitor the one-shot,
          we'll have to do it here.

          If READ is flagged as set explicitly (rather than just inherited
          from the session's default), we'll get the actual bool from the THD.
        */
        if (tx_read_flags != TX_READ_INHERIT)
        {
          if (tx_read_flags == TX_READ_ONLY)
            buf->append(STRING_WITH_LEN(" READ ONLY"));
          else
            buf->append(STRING_WITH_LEN(" READ WRITE"));
        }
        buf->append(STRING_WITH_LEN("; "));
      }
      else if (tx_read_flags != TX_READ_INHERIT)
      {
        /*
          "READ ONLY" / "READ WRITE"
          We could transform this to SET TRANSACTION even when it occurs
          in START TRANSACTION, but for now, we'll resysynthesize the original
          command as closely as possible.
        */
        buf->append(STRING_WITH_LEN("SET TRANSACTION "));
        if (tx_read_flags == TX_READ_ONLY)
          buf->append(STRING_WITH_LEN("READ ONLY; "));
        else
          buf->append(STRING_WITH_LEN("READ WRITE; "));
      }

      if ((tx_curr_state & TX_EXPLICIT) && is_xa)
      {
        XID *xid= &thd->transaction.xid_state.xid;
        long glen, blen;

        buf->append(STRING_WITH_LEN("XA START"));

        if ((glen= xid->gtrid_length) > 0)
        {
          buf->append(STRING_WITH_LEN(" '"));
          buf->append(xid->data, glen);

          if ((blen= xid->bqual_length) > 0)
          {
            buf->append(STRING_WITH_LEN("','"));
            buf->append(xid->data + glen, blen);
          }
          buf->append(STRING_WITH_LEN("'"));

          if (xid->formatID != 1)
          {
            buf->append(STRING_WITH_LEN(","));
            buf->append_ulonglong(xid->formatID);
          }
        }

        buf->append(STRING_WITH_LEN("; "));
      }

      // discard trailing space
      if (buf->length() > start)
        buf->length(buf->length() - 1);
    }

    {
      size_t length= buf->length() - start;
      uchar *place= (uchar *)(buf->ptr() + (start - 2));
      DBUG_ASSERT(length < 249); // in fact < 110
      DBUG_ASSERT(start >= 3);

      DBUG_ASSERT((place - 1)[0] == SESSION_TRACK_TRANSACTION_CHARACTERISTICS);
      /* Length of the overall entity. */
      place[0]= (uchar)length + 1;
      /* Transaction characteristics (length-encoded string). */
      place[1]= (uchar)length;
    }
  }

  reset();

  return false;
}


/**
  Reset the m_changed flag for next statement.
*/

void Transaction_state_tracker::reset()
{
  m_changed=  false;
  tx_reported_state=  tx_curr_state;
  tx_changed=  TX_CHG_NONE;
}


/**
  Helper function: turn table info into table access flag.
  Accepts table lock type and engine type flag (transactional/
  non-transactional), and returns the corresponding access flag
  out of TX_READ_TRX, TX_READ_UNSAFE, TX_WRITE_TRX, TX_WRITE_UNSAFE.

  @param thd [IN]           The thd handle
  @param set [IN]           The table's access/lock type
  @param set [IN]           Whether the table's engine is transactional

  @return                   The table access flag
*/

enum_tx_state Transaction_state_tracker::calc_trx_state(THD *thd,
                                                        thr_lock_type l,
                                                        bool has_trx)
{
  enum_tx_state      s;
  bool               read= (l <= TL_READ_NO_INSERT);

  if (read)
    s= has_trx ? TX_READ_TRX  : TX_READ_UNSAFE;
  else
    s= has_trx ? TX_WRITE_TRX : TX_WRITE_UNSAFE;

  return s;
}


/**
  Register the end of an (implicit or explicit) transaction.

  @param thd [IN]           The thd handle
*/
void Transaction_state_tracker::end_trx(THD *thd)
{
  DBUG_ASSERT(thd->variables.session_track_transaction_info > TX_TRACK_NONE);

  if ((!m_enabled) || (thd->state_flags & Open_tables_state::BACKUPS_AVAIL))
    return;

  if (tx_curr_state != TX_EMPTY)
  {
    if (tx_curr_state & TX_EXPLICIT)
      tx_changed  |= TX_CHG_CHISTICS;
    tx_curr_state &= TX_LOCKED_TABLES;
  }
  update_change_flags(thd);
}


/**
  Clear flags pertaining to the current statement or transaction.
  May be called repeatedly within the same execution cycle.

  @param thd [IN]           The thd handle.
  @param set [IN]           The flags to clear
*/

void Transaction_state_tracker::clear_trx_state(THD *thd, uint clear)
{
  if ((!m_enabled) || (thd->state_flags & Open_tables_state::BACKUPS_AVAIL))
    return;

  tx_curr_state &= ~clear;
  update_change_flags(thd);
}


/**
  Add flags pertaining to the current statement or transaction.
  May be called repeatedly within the same execution cycle,
  e.g. to add access info for more tables.

  @param thd [IN]           The thd handle.
  @param set [IN]           The flags to add
*/

void Transaction_state_tracker::add_trx_state(THD *thd, uint add)
{
  if ((!m_enabled) || (thd->state_flags & Open_tables_state::BACKUPS_AVAIL))
    return;

  if (add == TX_EXPLICIT)
  {
    /* Always send characteristic item (if tracked), always replace state. */
    tx_changed |= TX_CHG_CHISTICS;
    tx_curr_state = TX_EXPLICIT;
  }

  /*
    If we're not in an implicit or explicit transaction, but
    autocommit==0 and tables are accessed, we flag "implicit transaction."
  */
  else if (!(tx_curr_state & (TX_EXPLICIT|TX_IMPLICIT)) &&
           (thd->variables.option_bits & OPTION_NOT_AUTOCOMMIT) &&
           (add &
            (TX_READ_TRX | TX_READ_UNSAFE | TX_WRITE_TRX | TX_WRITE_UNSAFE)))
    tx_curr_state |= TX_IMPLICIT;

  /*
    Only flag state when in transaction or LOCK TABLES is added.
  */
  if ((tx_curr_state & (TX_EXPLICIT | TX_IMPLICIT)) ||
      (add & TX_LOCKED_TABLES))
    tx_curr_state |= add;

  update_change_flags(thd);
}


/**
  Add "unsafe statement" flag if applicable.

  @param thd [IN]           The thd handle.
  @param set [IN]           The flags to add
*/

void Transaction_state_tracker::add_trx_state_from_thd(THD *thd)
{
  if (m_enabled)
  {
    if (thd->lex->is_stmt_unsafe())
      add_trx_state(thd, TX_STMT_UNSAFE);
  }
}


/**
  Set read flags (read only/read write) pertaining to the next
  transaction.

  @param thd [IN]           The thd handle.
  @param set [IN]           The flags to set
*/

void Transaction_state_tracker::set_read_flags(THD *thd,
                                               enum enum_tx_read_flags flags)
{
  if (m_enabled && (tx_read_flags != flags))
  {
    tx_read_flags = flags;
    tx_changed   |= TX_CHG_CHISTICS;
    mark_as_changed(thd, NULL);
  }
}


/**
  Set isolation level pertaining to the next transaction.

  @param thd [IN]           The thd handle.
  @param set [IN]           The isolation level to set
*/

void Transaction_state_tracker::set_isol_level(THD *thd,
                                               enum enum_tx_isol_level level)
{
  if (m_enabled && (tx_isol_level != level))
  {
    tx_isol_level = level;
    tx_changed   |= TX_CHG_CHISTICS;
    mark_as_changed(thd, NULL);
  }
}


///////////////////////////////////////////////////////////////////////////////

Session_state_change_tracker::Session_state_change_tracker()
{
  m_changed= false;
}

/**
  @Enable/disable the tracker based on @@session_track_state_change value.

  @param thd [IN]           The thd handle.
  @return                   false (always)

**/

bool Session_state_change_tracker::update(THD *thd, set_var *)
{
  m_enabled= thd->variables.session_track_state_change;
  return false;
}

/**
  Store the '1' in the specified buffer when state is changed.

  @param thd [IN]           The thd handle.
  @paran buf [INOUT]        Buffer to store the information to.

  @reval  false Success
  @retval true  Error
**/

bool Session_state_change_tracker::store(THD *thd, String *buf)
{
  if (unlikely((1 + 1 + 1 + buf->length() >= MAX_PACKET_LENGTH) ||
               buf->reserve(1 + 1 + 1, EXTRA_ALLOC)))
    return true;

  compile_time_assert(SESSION_TRACK_STATE_CHANGE < 251);
  /* Session state type (SESSION_TRACK_STATE_CHANGE) */
  buf->q_append((char)SESSION_TRACK_STATE_CHANGE);

  /* Length of the overall entity (1 byte) */
  buf->q_append('\1');

  DBUG_ASSERT(is_state_changed(thd));
  buf->q_append('1');

  reset();

  return false;
}


/**
  Reset the m_changed flag for next statement.
*/

void Session_state_change_tracker::reset()
{
  m_changed= false;
}


/**
  Find if there is a session state change.
*/

bool Session_state_change_tracker::is_state_changed(THD *)
{
  return m_changed;
}

///////////////////////////////////////////////////////////////////////////////

/**
  @brief Initialize session tracker objects.
*/

Session_tracker::Session_tracker()
{
  /* track data ID fit into one byte in net coding */
  compile_time_assert(SESSION_TRACK_always_at_the_end < 251);
  /* one tracker could serv several tracking data */
  compile_time_assert((uint)SESSION_TRACK_always_at_the_end >=
                      (uint)SESSION_TRACKER_END);

  for (int i= 0; i < SESSION_TRACKER_END; i++)
    m_trackers[i]= NULL;
}


/**
  @brief Enables the tracker objects.

  @param thd [IN]    The thread handle.

  @return            void
*/

void Session_tracker::enable(THD *thd)
{
  /*
    Originally and correctly this allocation was in the constructor and
    deallocation in the destructor, but in this case memory counting
    system works incorrectly (for example in INSERT DELAYED thread)
  */
  deinit();
  m_trackers[SESSION_SYSVARS_TRACKER]=
    new (std::nothrow) Session_sysvars_tracker();
  m_trackers[CURRENT_SCHEMA_TRACKER]=
    new (std::nothrow) Current_schema_tracker;
  m_trackers[SESSION_STATE_CHANGE_TRACKER]=
    new (std::nothrow) Session_state_change_tracker;
  m_trackers[SESSION_GTIDS_TRACKER]=
    new (std::nothrow) Not_implemented_tracker;
  m_trackers[TRANSACTION_INFO_TRACKER]=
    new (std::nothrow) Transaction_state_tracker;

  for (int i= 0; i < SESSION_TRACKER_END; i++)
    m_trackers[i]->enable(thd);
}


/**
  Method called during the server startup to verify the contents
  of @@session_track_system_variables.

  @retval false Success
  @retval true  Failure
*/

bool Session_tracker::server_boot_verify(CHARSET_INFO *char_set)
{
  bool result;
  LEX_STRING tmp;
  tmp.str= global_system_variables.session_track_system_variables;
  tmp.length= safe_strlen(tmp.str);
  result=
    Session_sysvars_tracker::server_init_check(NULL, char_set, tmp);
  return result;
}


/**
  @brief Store all change information in the specified buffer.

  @param thd [IN]           The thd handle.
  @param buf [OUT]          Reference to the string buffer to which the state
                            change data needs to be written.
*/

void Session_tracker::store(THD *thd, String *buf)
{
  size_t start;

  /*
    Probably most track result will fit in 251 byte so lets made it at
    least efficient. We allocate 1 byte for length and then will move
    string if there is more.
  */
  buf->append('\0');
  start= buf->length();

  /* Get total length. */
  for (int i= 0; i < SESSION_TRACKER_END; i++)
  {
    if (m_trackers[i]->is_changed() &&
        m_trackers[i]->store(thd, buf))
    {
      buf->length(start); // it is safer to have 0-length block in case of error
      return;
    }
  }

  size_t length= buf->length() - start;
  uchar *data= (uchar *)(buf->ptr() + start);
  uint size;

  if ((size= net_length_size(length)) != 1)
  {
    if (buf->reserve(size - 1, EXTRA_ALLOC))
    {
      buf->length(start); // it is safer to have 0-length block in case of error
      return;
    }
    memmove(data + (size - 1), data, length);
  }

  net_store_length(data - 1, length);
}

#endif //EMBEDDED_LIBRARY