summaryrefslogtreecommitdiff
path: root/sql/sql_servers.cc
blob: c46a01cd53478d7b27ddcbca35530433ca2672ea (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
/* Copyright (C) 2000-2003 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; 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */


/*
  The servers are saved in the system table "servers"
  
  Currently, when the user performs an ALTER SERVER or a DROP SERVER
  operation, it will cause all open tables which refer to the named
  server connection to be flushed. This may cause some undesirable
  behaviour with regard to currently running transactions. It is 
  expected that the DBA knows what s/he is doing when s/he performs
  the ALTER SERVER or DROP SERVER operation.
  
  TODO:
  It is desirable for us to implement a callback mechanism instead where
  callbacks can be registered for specific server protocols. The callback
  will be fired when such a server name has been created/altered/dropped
  or when statistics are to be gathered such as how many actual connections.
  Storage engines etc will be able to make use of the callback so that
  currently running transactions etc will not be disrupted.
*/

#include "mysql_priv.h"
#include "hash_filo.h"
#include <m_ctype.h>
#include <stdarg.h>
#include "sp_head.h"
#include "sp.h"
#include "transaction.h"

/*
  We only use 1 mutex to guard the data structures - THR_LOCK_servers.
  Read locked when only reading data and write-locked for all other access.
*/

static HASH servers_cache;
static MEM_ROOT mem;
static rw_lock_t THR_LOCK_servers;

static bool get_server_from_table_to_cache(TABLE *table);

/* insert functions */
static int insert_server(THD *thd, FOREIGN_SERVER *server_options);
static int insert_server_record(TABLE *table, FOREIGN_SERVER *server);
static int insert_server_record_into_cache(FOREIGN_SERVER *server);
static FOREIGN_SERVER *
prepare_server_struct_for_insert(LEX_SERVER_OPTIONS *server_options);
/* drop functions */ 
static int delete_server_record(TABLE *table,
                                char *server_name,
                                size_t server_name_length);
static int delete_server_record_in_cache(LEX_SERVER_OPTIONS *server_options);

/* update functions */
static void prepare_server_struct_for_update(LEX_SERVER_OPTIONS *server_options,
                                             FOREIGN_SERVER *existing,
                                             FOREIGN_SERVER *altered);
static int update_server(THD *thd, FOREIGN_SERVER *existing, 
					     FOREIGN_SERVER *altered);
static int update_server_record(TABLE *table, FOREIGN_SERVER *server);
static int update_server_record_in_cache(FOREIGN_SERVER *existing,
                                         FOREIGN_SERVER *altered);
/* utility functions */
static void merge_server_struct(FOREIGN_SERVER *from, FOREIGN_SERVER *to);



static uchar *servers_cache_get_key(FOREIGN_SERVER *server, size_t *length,
			       my_bool not_used __attribute__((unused)))
{
  DBUG_ENTER("servers_cache_get_key");
  DBUG_PRINT("info", ("server_name_length %d server_name %s",
                      server->server_name_length,
                      server->server_name));

  *length= (uint) server->server_name_length;
  DBUG_RETURN((uchar*) server->server_name);
}


/*
  Initialize structures responsible for servers used in federated
  server scheme information for them from the server
  table in the 'mysql' database.

  SYNOPSIS
    servers_init()
      dont_read_server_table  TRUE if we want to skip loading data from
                            server table and disable privilege checking.

  NOTES
    This function is mostly responsible for preparatory steps, main work
    on initialization and grants loading is done in servers_reload().

  RETURN VALUES
    0	ok
    1	Could not initialize servers
*/

bool servers_init(bool dont_read_servers_table)
{
  THD  *thd;
  bool return_val= FALSE;
  DBUG_ENTER("servers_init");

  /* init the mutex */
  if (my_rwlock_init(&THR_LOCK_servers, NULL))
    DBUG_RETURN(TRUE);

  /* initialise our servers cache */
  if (my_hash_init(&servers_cache, system_charset_info, 32, 0, 0,
                   (my_hash_get_key) servers_cache_get_key, 0, 0))
  {
    return_val= TRUE; /* we failed, out of memory? */
    goto end;
  }

  /* Initialize the mem root for data */
  init_sql_alloc(&mem, ACL_ALLOC_BLOCK_SIZE, 0);

  if (dont_read_servers_table)
    goto end;

  /*
    To be able to run this from boot, we allocate a temporary THD
  */
  if (!(thd=new THD))
    DBUG_RETURN(TRUE);
  thd->thread_stack= (char*) &thd;
  thd->store_globals();
  lex_start(thd);
  /*
    It is safe to call servers_reload() since servers_* arrays and hashes which
    will be freed there are global static objects and thus are initialized
    by zeros at startup.
  */
  return_val= servers_reload(thd);
  delete thd;
  /* Remember that we don't have a THD */
  my_pthread_setspecific_ptr(THR_THD,  0);

end:
  DBUG_RETURN(return_val);
}

/*
  Initialize server structures

  SYNOPSIS
    servers_load()
      thd     Current thread
      tables  List containing open "mysql.servers"

  RETURN VALUES
    FALSE  Success
    TRUE   Error

  TODO
    Revert back to old list if we failed to load new one.
*/

static bool servers_load(THD *thd, TABLE_LIST *tables)
{
  TABLE *table;
  READ_RECORD read_record_info;
  bool return_val= TRUE;
  DBUG_ENTER("servers_load");

  my_hash_reset(&servers_cache);
  free_root(&mem, MYF(0));
  init_sql_alloc(&mem, ACL_ALLOC_BLOCK_SIZE, 0);

  init_read_record(&read_record_info,thd,table=tables[0].table,NULL,1,0, 
                   FALSE);
  while (!(read_record_info.read_record(&read_record_info)))
  {
    /* return_val is already TRUE, so no need to set */
    if ((get_server_from_table_to_cache(table)))
      goto end;
  }

  return_val= FALSE;

end:
  end_read_record(&read_record_info);
  DBUG_RETURN(return_val);
}


/*
  Forget current servers cache and read new servers 
  from the conneciton table.

  SYNOPSIS
    servers_reload()
      thd  Current thread

  NOTE
    All tables of calling thread which were open and locked by LOCK TABLES
    statement will be unlocked and closed.
    This function is also used for initialization of structures responsible
    for user/db-level privilege checking.

  RETURN VALUE
    FALSE  Success
    TRUE   Failure
*/

bool servers_reload(THD *thd)
{
  TABLE_LIST tables[1];
  bool return_val= TRUE;
  DBUG_ENTER("servers_reload");

  DBUG_PRINT("info", ("locking servers_cache"));
  rw_wrlock(&THR_LOCK_servers);

  bzero((char*) tables, sizeof(tables));
  tables[0].alias= tables[0].table_name= (char*) "servers";
  tables[0].db= (char*) "mysql";
  tables[0].lock_type= TL_READ;
  alloc_mdl_requests(tables, thd->mem_root);

  if (simple_open_n_lock_tables(thd, tables))
  {
    sql_print_error("Can't open and lock privilege tables: %s",
		    thd->stmt_da->message());
    goto end;
  }

  if ((return_val= servers_load(thd, tables)))
  {					// Error. Revert to old list
    /* blast, for now, we have no servers, discuss later way to preserve */

    DBUG_PRINT("error",("Reverting to old privileges"));
    servers_free();
  }

end:
  trans_commit_implicit(thd);
  close_thread_tables(thd);
  if (!thd->locked_tables_mode)
    thd->mdl_context.release_all_locks();
  DBUG_PRINT("info", ("unlocking servers_cache"));
  rw_unlock(&THR_LOCK_servers);
  DBUG_RETURN(return_val);
}


/*
  Initialize structures responsible for servers used in federated
  server scheme information for them from the server
  table in the 'mysql' database.

  SYNOPSIS
    get_server_from_table_to_cache()
      TABLE *table         open table pointer


  NOTES
    This function takes a TABLE pointer (pointing to an opened
    table). With this open table, a FOREIGN_SERVER struct pointer
    is allocated into root memory, then each member of the FOREIGN_SERVER
    struct is populated. A char pointer takes the return value of get_field
    for each column we're interested in obtaining, and if that pointer
    isn't 0x0, the FOREIGN_SERVER member is set to that value, otherwise,
    is set to the value of an empty string, since get_field would set it to
    0x0 if the column's value is empty, even if the default value for that
    column is NOT NULL.

  RETURN VALUES
    0	ok
    1	could not insert server struct into global servers cache
*/

static bool 
get_server_from_table_to_cache(TABLE *table)
{
  /* alloc a server struct */
  char *ptr;
  char * const blank= (char*)"";
  FOREIGN_SERVER *server= (FOREIGN_SERVER *)alloc_root(&mem,
                                                       sizeof(FOREIGN_SERVER));
  DBUG_ENTER("get_server_from_table_to_cache");
  table->use_all_columns();

  /* get each field into the server struct ptr */
  server->server_name= get_field(&mem, table->field[0]);
  server->server_name_length= (uint) strlen(server->server_name);
  ptr= get_field(&mem, table->field[1]);
  server->host= ptr ? ptr : blank;
  ptr= get_field(&mem, table->field[2]);
  server->db= ptr ? ptr : blank;
  ptr= get_field(&mem, table->field[3]);
  server->username= ptr ? ptr : blank;
  ptr= get_field(&mem, table->field[4]);
  server->password= ptr ? ptr : blank;
  ptr= get_field(&mem, table->field[5]);
  server->sport= ptr ? ptr : blank;

  server->port= server->sport ? atoi(server->sport) : 0;

  ptr= get_field(&mem, table->field[6]);
  server->socket= ptr && strlen(ptr) ? ptr : blank;
  ptr= get_field(&mem, table->field[7]);
  server->scheme= ptr ? ptr : blank;
  ptr= get_field(&mem, table->field[8]);
  server->owner= ptr ? ptr : blank;
  DBUG_PRINT("info", ("server->server_name %s", server->server_name));
  DBUG_PRINT("info", ("server->host %s", server->host));
  DBUG_PRINT("info", ("server->db %s", server->db));
  DBUG_PRINT("info", ("server->username %s", server->username));
  DBUG_PRINT("info", ("server->password %s", server->password));
  DBUG_PRINT("info", ("server->socket %s", server->socket));
  if (my_hash_insert(&servers_cache, (uchar*) server))
  {
    DBUG_PRINT("info", ("had a problem inserting server %s at %lx",
                        server->server_name, (long unsigned int) server));
    // error handling needed here
    DBUG_RETURN(TRUE);
  }
  DBUG_RETURN(FALSE);
}


/*
  SYNOPSIS
    insert_server()
      THD   *thd     - thread pointer
      FOREIGN_SERVER *server - pointer to prepared FOREIGN_SERVER struct

  NOTES
    This function takes a server object that is has all members properly
    prepared, ready to be inserted both into the mysql.servers table and
    the servers cache.
	
    THR_LOCK_servers must be write locked.

  RETURN VALUES
    0  - no error
    other - error code
*/

static int 
insert_server(THD *thd, FOREIGN_SERVER *server)
{
  int error= -1;
  TABLE_LIST tables;
  TABLE *table;

  DBUG_ENTER("insert_server");

  bzero((char*) &tables, sizeof(tables));
  tables.db= (char*) "mysql";
  tables.alias= tables.table_name= (char*) "servers";
  alloc_mdl_requests(&tables, thd->mem_root);

  /* need to open before acquiring THR_LOCK_plugin or it will deadlock */
  if (! (table= open_ltable(thd, &tables, TL_WRITE, 0)))
    goto end;

  /* insert the server into the table */
  if ((error= insert_server_record(table, server)))
    goto end;

  /* insert the server into the cache */
  if ((error= insert_server_record_into_cache(server)))
    goto end;

end:
  DBUG_RETURN(error);
}


/*
  SYNOPSIS
    int insert_server_record_into_cache()
      FOREIGN_SERVER *server

  NOTES
    This function takes a FOREIGN_SERVER pointer to an allocated (root mem)
    and inserts it into the global servers cache

    THR_LOCK_servers must be write locked.

  RETURN VALUE
    0   - no error
    >0  - error code

*/

static int 
insert_server_record_into_cache(FOREIGN_SERVER *server)
{
  int error=0;
  DBUG_ENTER("insert_server_record_into_cache");
  /*
    We succeded in insertion of the server to the table, now insert
    the server to the cache
  */
  DBUG_PRINT("info", ("inserting server %s at %lx, length %d",
                        server->server_name, (long unsigned int) server,
                        server->server_name_length));
  if (my_hash_insert(&servers_cache, (uchar*) server))
  {
    DBUG_PRINT("info", ("had a problem inserting server %s at %lx",
                        server->server_name, (long unsigned int) server));
    // error handling needed here
    error= 1;
  }
  DBUG_RETURN(error);
}


/*
  SYNOPSIS
    store_server_fields()
      TABLE *table
      FOREIGN_SERVER *server

  NOTES
    This function takes an opened table object, and a pointer to an 
    allocated FOREIGN_SERVER struct, and then stores each member of
    the FOREIGN_SERVER to the appropriate fields in the table, in 
    advance of insertion into the mysql.servers table

  RETURN VALUE
    VOID

*/

static void 
store_server_fields(TABLE *table, FOREIGN_SERVER *server)
{

  table->use_all_columns();
  /*
    "server" has already been prepped by prepare_server_struct_for_<>
    so, all we need to do is check if the value is set (> -1 for port)

    If this happens to be an update, only the server members that 
    have changed will be set. If an insert, then all will be set,
    even if with empty strings
  */
  if (server->host)
    table->field[1]->store(server->host,
                           (uint) strlen(server->host), system_charset_info);
  if (server->db)
    table->field[2]->store(server->db,
                           (uint) strlen(server->db), system_charset_info);
  if (server->username)
    table->field[3]->store(server->username,
                           (uint) strlen(server->username), system_charset_info);
  if (server->password)
    table->field[4]->store(server->password,
                           (uint) strlen(server->password), system_charset_info);
  if (server->port > -1)
    table->field[5]->store(server->port);

  if (server->socket)
    table->field[6]->store(server->socket,
                           (uint) strlen(server->socket), system_charset_info);
  if (server->scheme)
    table->field[7]->store(server->scheme,
                           (uint) strlen(server->scheme), system_charset_info);
  if (server->owner)
    table->field[8]->store(server->owner,
                           (uint) strlen(server->owner), system_charset_info);
}

/*
  SYNOPSIS
    insert_server_record()
      TABLE *table
      FOREIGN_SERVER *server

  NOTES
    This function takes the arguments of an open table object and a pointer
    to an allocated FOREIGN_SERVER struct. It stores the server_name into
    the first field of the table (the primary key, server_name column). With
    this, index_read_idx is called, if the record is found, an error is set
    to ER_FOREIGN_SERVER_EXISTS (the server with that server name exists in the
    table), if not, then store_server_fields stores all fields of the
    FOREIGN_SERVER to the table, then ha_write_row is inserted. If an error
    is encountered in either index_read_idx or ha_write_row, then that error
    is returned

  RETURN VALUE
    0 - no errors
    >0 - error code

  */

static
int insert_server_record(TABLE *table, FOREIGN_SERVER *server)
{
  int error;
  DBUG_ENTER("insert_server_record");
  table->use_all_columns();

  empty_record(table);

  /* set the field that's the PK to the value we're looking for */
  table->field[0]->store(server->server_name,
                         server->server_name_length,
                         system_charset_info);

  /* read index until record is that specified in server_name */
  if ((error= table->file->index_read_idx_map(table->record[0], 0,
                                              (uchar *)table->field[0]->ptr,
                                              HA_WHOLE_KEY,
                                              HA_READ_KEY_EXACT)))
  {
    /* if not found, err */
    if (error != HA_ERR_KEY_NOT_FOUND && error != HA_ERR_END_OF_FILE)
    {
      table->file->print_error(error, MYF(0));
      error= 1;
    }
    /* store each field to be inserted */
    store_server_fields(table, server);

    DBUG_PRINT("info",("record for server '%s' not found!",
                       server->server_name));
    /* write/insert the new server */
    if ((error=table->file->ha_write_row(table->record[0])))
    {
      table->file->print_error(error, MYF(0));
    }
    else
      error= 0;
  }
  else
    error= ER_FOREIGN_SERVER_EXISTS;
  DBUG_RETURN(error);
}

/*
  SYNOPSIS
    drop_server()
      THD *thd
      LEX_SERVER_OPTIONS *server_options

  NOTES
    This function takes as its arguments a THD object pointer and a pointer
    to a LEX_SERVER_OPTIONS struct from the parser. The member 'server_name'
    of this LEX_SERVER_OPTIONS struct contains the value of the server to be
    deleted. The mysql.servers table is opened via open_ltable, a table object
    returned, the servers cache mutex locked, then delete_server_record is
    called with this table object and LEX_SERVER_OPTIONS server_name and
    server_name_length passed, containing the name of the server to be
    dropped/deleted, then delete_server_record_in_cache is called to delete
    the server from the servers cache.

  RETURN VALUE
    0 - no error
    > 0 - error code
*/

int drop_server(THD *thd, LEX_SERVER_OPTIONS *server_options)
{
  int error;
  TABLE_LIST tables;
  TABLE *table;
  LEX_STRING name= { server_options->server_name, 
                     server_options->server_name_length };

  DBUG_ENTER("drop_server");
  DBUG_PRINT("info", ("server name server->server_name %s",
                      server_options->server_name));

  bzero((char*) &tables, sizeof(tables));
  tables.db= (char*) "mysql";
  tables.alias= tables.table_name= (char*) "servers";
  alloc_mdl_requests(&tables, thd->mem_root);

  rw_wrlock(&THR_LOCK_servers);

  /* hit the memory hit first */
  if ((error= delete_server_record_in_cache(server_options)))
    goto end;

  if (! (table= open_ltable(thd, &tables, TL_WRITE, 0)))
  {
    error= my_errno;
    goto end;
  }

  error= delete_server_record(table, name.str, name.length);

  /* close the servers table before we call closed_cached_connection_tables */
  close_thread_tables(thd);

  if (close_cached_connection_tables(thd, TRUE, &name))
  {
    push_warning_printf(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
                        ER_UNKNOWN_ERROR, "Server connection in use");
  }

end:
  rw_unlock(&THR_LOCK_servers);
  DBUG_RETURN(error);
}


/*

  SYNOPSIS
    delete_server_record_in_cache()
      LEX_SERVER_OPTIONS *server_options

  NOTES
    This function's  argument is a LEX_SERVER_OPTIONS struct pointer. This
    function uses the "server_name" and "server_name_length" members of the
    lex->server_options to search for the server in the servers_cache. Upon
    returned the server (pointer to a FOREIGN_SERVER struct), it then deletes
    that server from the servers_cache hash.

  RETURN VALUE
    0 - no error

*/

static int 
delete_server_record_in_cache(LEX_SERVER_OPTIONS *server_options)
{
  int error= ER_FOREIGN_SERVER_DOESNT_EXIST;
  FOREIGN_SERVER *server;
  DBUG_ENTER("delete_server_record_in_cache");

  DBUG_PRINT("info",("trying to obtain server name %s length %d",
                     server_options->server_name,
                     server_options->server_name_length));


  if (!(server= (FOREIGN_SERVER *)
        my_hash_search(&servers_cache,
                       (uchar*) server_options->server_name,
                       server_options->server_name_length)))
  {
    DBUG_PRINT("info", ("server_name %s length %d not found!",
                        server_options->server_name,
                        server_options->server_name_length));
    goto end;
  }
  /*
    We succeded in deletion of the server to the table, now delete
    the server from the cache
  */
  DBUG_PRINT("info",("deleting server %s length %d",
                     server->server_name,
                     server->server_name_length));

  my_hash_delete(&servers_cache, (uchar*) server);

  error= 0;

end:
  DBUG_RETURN(error);
}


/*

  SYNOPSIS
    update_server()
      THD *thd
      FOREIGN_SERVER *existing
      FOREIGN_SERVER *altered

  NOTES
    This function takes as arguments a THD object pointer, and two pointers,
    one pointing to the existing FOREIGN_SERVER struct "existing" (which is
    the current record as it is) and another pointer pointing to the
    FOREIGN_SERVER struct with the members containing the modified/altered
    values that need to be updated in both the mysql.servers table and the 
    servers_cache. It opens a table, passes the table and the altered
    FOREIGN_SERVER pointer, which will be used to update the mysql.servers 
    table for the particular server via the call to update_server_record,
    and in the servers_cache via update_server_record_in_cache. 

    THR_LOCK_servers must be write locked.

  RETURN VALUE
    0 - no error
    >0 - error code

*/

int update_server(THD *thd, FOREIGN_SERVER *existing, FOREIGN_SERVER *altered)
{
  int error;
  TABLE *table;
  TABLE_LIST tables;
  DBUG_ENTER("update_server");

  bzero((char*) &tables, sizeof(tables));
  tables.db= (char*)"mysql";
  tables.alias= tables.table_name= (char*)"servers";
  alloc_mdl_requests(&tables, thd->mem_root);

  if (!(table= open_ltable(thd, &tables, TL_WRITE, 0)))
  {
    error= my_errno;
    goto end;
  }

  if ((error= update_server_record(table, altered)))
    goto end;

  error= update_server_record_in_cache(existing, altered);

  /*
	Perform a reload so we don't have a 'hole' in our mem_root
  */
  servers_load(thd, &tables);

end:
  DBUG_RETURN(error);
}


/*

  SYNOPSIS
    update_server_record_in_cache()
      FOREIGN_SERVER *existing
      FOREIGN_SERVER *altered

  NOTES
    This function takes as an argument the FOREIGN_SERVER structi pointer
    for the existing server and the FOREIGN_SERVER struct populated with only 
    the members which have been updated. It then "merges" the "altered" struct
    members to the existing server, the existing server then represents an
    updated server. Then, the existing record is deleted from the servers_cache
    HASH, then the updated record inserted, in essence replacing the old
    record.

    THR_LOCK_servers must be write locked.

  RETURN VALUE
    0 - no error
    1 - error

*/

int update_server_record_in_cache(FOREIGN_SERVER *existing,
                                  FOREIGN_SERVER *altered)
{
  int error= 0;
  DBUG_ENTER("update_server_record_in_cache");

  /*
    update the members that haven't been change in the altered server struct
    with the values of the existing server struct
  */
  merge_server_struct(existing, altered);

  /*
    delete the existing server struct from the server cache
  */
  my_hash_delete(&servers_cache, (uchar*)existing);

  /*
    Insert the altered server struct into the server cache
  */
  if (my_hash_insert(&servers_cache, (uchar*)altered))
  {
    DBUG_PRINT("info", ("had a problem inserting server %s at %lx",
                        altered->server_name, (long unsigned int) altered));
    error= ER_OUT_OF_RESOURCES;
  }

  DBUG_RETURN(error);
}


/*

  SYNOPSIS
    merge_server_struct()
      FOREIGN_SERVER *from
      FOREIGN_SERVER *to

  NOTES
    This function takes as its arguments two pointers each to an allocated
    FOREIGN_SERVER struct. The first FOREIGN_SERVER struct represents the struct
    that we will obtain values from (hence the name "from"), the second
    FOREIGN_SERVER struct represents which FOREIGN_SERVER struct we will be
    "copying" any members that have a value to (hence the name "to")

  RETURN VALUE
    VOID

*/

void merge_server_struct(FOREIGN_SERVER *from, FOREIGN_SERVER *to)
{
  DBUG_ENTER("merge_server_struct");
  if (!to->host)
    to->host= strdup_root(&mem, from->host);
  if (!to->db)
    to->db= strdup_root(&mem, from->db);
  if (!to->username)
    to->username= strdup_root(&mem, from->username);
  if (!to->password)
    to->password= strdup_root(&mem, from->password);
  if (to->port == -1)
    to->port= from->port;
  if (!to->socket && from->socket)
    to->socket= strdup_root(&mem, from->socket);
  if (!to->scheme && from->scheme)
    to->scheme= strdup_root(&mem, from->scheme);
  if (!to->owner)
    to->owner= strdup_root(&mem, from->owner);

  DBUG_VOID_RETURN;
}


/*

  SYNOPSIS
    update_server_record()
      TABLE *table
      FOREIGN_SERVER *server

  NOTES
    This function takes as its arguments an open TABLE pointer, and a pointer
    to an allocated FOREIGN_SERVER structure representing an updated record
    which needs to be inserted. The primary key, server_name is stored to field
    0, then index_read_idx is called to read the index to that record, the
    record then being ready to be updated, if found. If not found an error is
    set and error message printed. If the record is found, store_record is
    called, then store_server_fields stores each field from the the members of
    the updated FOREIGN_SERVER struct.

  RETURN VALUE
    0 - no error

*/


static int 
update_server_record(TABLE *table, FOREIGN_SERVER *server)
{
  int error=0;
  DBUG_ENTER("update_server_record");
  table->use_all_columns();
  /* set the field that's the PK to the value we're looking for */
  table->field[0]->store(server->server_name,
                         server->server_name_length,
                         system_charset_info);

  if ((error= table->file->index_read_idx_map(table->record[0], 0,
                                              (uchar *)table->field[0]->ptr,
                                              ~(longlong)0,
                                              HA_READ_KEY_EXACT)))
  {
    if (error != HA_ERR_KEY_NOT_FOUND && error != HA_ERR_END_OF_FILE)
      table->file->print_error(error, MYF(0));
    DBUG_PRINT("info",("server not found!"));
    error= ER_FOREIGN_SERVER_DOESNT_EXIST;
  }
  else
  {
    /* ok, so we can update since the record exists in the table */
    store_record(table,record[1]);
    store_server_fields(table, server);
    if ((error=table->file->ha_update_row(table->record[1],
                                          table->record[0])) &&
        error != HA_ERR_RECORD_IS_THE_SAME)
    {
      DBUG_PRINT("info",("problems with ha_update_row %d", error));
      goto end;
    }
    else
      error= 0;
  }

end:
  DBUG_RETURN(error);
}


/*

  SYNOPSIS
    delete_server_record()
      TABLE *table
      char *server_name
      int server_name_length

  NOTES

  RETURN VALUE
    0 - no error

*/

static int 
delete_server_record(TABLE *table,
                     char *server_name, size_t server_name_length)
{
  int error;
  DBUG_ENTER("delete_server_record");
  table->use_all_columns();

  /* set the field that's the PK to the value we're looking for */
  table->field[0]->store(server_name, server_name_length, system_charset_info);

  if ((error= table->file->index_read_idx_map(table->record[0], 0,
                                          (uchar *)table->field[0]->ptr,
                                          HA_WHOLE_KEY,
                                          HA_READ_KEY_EXACT)))
  {
    if (error != HA_ERR_KEY_NOT_FOUND && error != HA_ERR_END_OF_FILE)
      table->file->print_error(error, MYF(0));
    DBUG_PRINT("info",("server not found!"));
    error= ER_FOREIGN_SERVER_DOESNT_EXIST;
  }
  else
  {
    if ((error= table->file->ha_delete_row(table->record[0])))
      table->file->print_error(error, MYF(0));
  }

  DBUG_RETURN(error);
}

/*

  SYNOPSIS
    create_server()
        THD *thd
        LEX_SERVER_OPTIONS *server_options

  NOTES

  RETURN VALUE
    0 - no error

*/

int create_server(THD *thd, LEX_SERVER_OPTIONS *server_options)
{
  int error= ER_FOREIGN_SERVER_EXISTS;
  FOREIGN_SERVER *server;

  DBUG_ENTER("create_server");
  DBUG_PRINT("info", ("server_options->server_name %s",
                      server_options->server_name));

  rw_wrlock(&THR_LOCK_servers);

  /* hit the memory first */
  if (my_hash_search(&servers_cache, (uchar*) server_options->server_name,
                     server_options->server_name_length))
    goto end;


  if (!(server= prepare_server_struct_for_insert(server_options)))
  {
    /* purecov: begin inspected */
    error= ER_OUT_OF_RESOURCES;
    goto end;
    /* purecov: end */
  }

  error= insert_server(thd, server);

  DBUG_PRINT("info", ("error returned %d", error));

end:
  rw_unlock(&THR_LOCK_servers);
  DBUG_RETURN(error);
}


/*

  SYNOPSIS
    alter_server()
      THD *thd
      LEX_SERVER_OPTIONS *server_options

  NOTES

  RETURN VALUE
    0 - no error

*/

int alter_server(THD *thd, LEX_SERVER_OPTIONS *server_options)
{
  int error= ER_FOREIGN_SERVER_DOESNT_EXIST;
  FOREIGN_SERVER *altered, *existing;
  LEX_STRING name= { server_options->server_name, 
                     server_options->server_name_length };
  DBUG_ENTER("alter_server");
  DBUG_PRINT("info", ("server_options->server_name %s",
                      server_options->server_name));

  rw_wrlock(&THR_LOCK_servers);

  if (!(existing= (FOREIGN_SERVER *) my_hash_search(&servers_cache,
                                                    (uchar*) name.str,
                                                    name.length)))
    goto end;

  altered= (FOREIGN_SERVER *)alloc_root(&mem,
                                        sizeof(FOREIGN_SERVER));

  prepare_server_struct_for_update(server_options, existing, altered);

  error= update_server(thd, existing, altered);

  /* close the servers table before we call closed_cached_connection_tables */
  close_thread_tables(thd);

  if (close_cached_connection_tables(thd, FALSE, &name))
  {
    push_warning_printf(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
                        ER_UNKNOWN_ERROR, "Server connection in use");
  }

end:
  DBUG_PRINT("info", ("error returned %d", error));
  rw_unlock(&THR_LOCK_servers);
  DBUG_RETURN(error);
}


/*

  SYNOPSIS
    prepare_server_struct_for_insert()
      LEX_SERVER_OPTIONS *server_options

  NOTES
    As FOREIGN_SERVER members are allocated on mem_root, we do not need to
    free them in case of error.

  RETURN VALUE
    On success filled FOREIGN_SERVER, or NULL in case out of memory.

*/

static FOREIGN_SERVER *
prepare_server_struct_for_insert(LEX_SERVER_OPTIONS *server_options)
{
  char *unset_ptr= (char*)"";
  FOREIGN_SERVER *server;
  DBUG_ENTER("prepare_server_struct");

  if (!(server= (FOREIGN_SERVER *)alloc_root(&mem, sizeof(FOREIGN_SERVER))))
    DBUG_RETURN(NULL); /* purecov: inspected */

  /* these two MUST be set */
  if (!(server->server_name= strdup_root(&mem, server_options->server_name)))
    DBUG_RETURN(NULL); /* purecov: inspected */
  server->server_name_length= server_options->server_name_length;

  if (!(server->host= server_options->host ?
          strdup_root(&mem, server_options->host) : unset_ptr))
    DBUG_RETURN(NULL); /* purecov: inspected */

  if (!(server->db= server_options->db ?
          strdup_root(&mem, server_options->db) : unset_ptr))
    DBUG_RETURN(NULL); /* purecov: inspected */

  if (!(server->username= server_options->username ?
          strdup_root(&mem, server_options->username) : unset_ptr))
    DBUG_RETURN(NULL); /* purecov: inspected */

  if (!(server->password= server_options->password ?
          strdup_root(&mem, server_options->password) : unset_ptr))
    DBUG_RETURN(NULL); /* purecov: inspected */

  /* set to 0 if not specified */
  server->port= server_options->port > -1 ?
    server_options->port : 0;

  if (!(server->socket= server_options->socket ?
          strdup_root(&mem, server_options->socket) : unset_ptr))
    DBUG_RETURN(NULL); /* purecov: inspected */

  if (!(server->scheme= server_options->scheme ?
          strdup_root(&mem, server_options->scheme) : unset_ptr))
    DBUG_RETURN(NULL); /* purecov: inspected */

  if (!(server->owner= server_options->owner ?
          strdup_root(&mem, server_options->owner) : unset_ptr))
    DBUG_RETURN(NULL); /* purecov: inspected */

  DBUG_RETURN(server);
}

/*

  SYNOPSIS
    prepare_server_struct_for_update()
      LEX_SERVER_OPTIONS *server_options

  NOTES

  RETURN VALUE
    0 - no error

*/

static void
prepare_server_struct_for_update(LEX_SERVER_OPTIONS *server_options,
                                 FOREIGN_SERVER *existing,
                                 FOREIGN_SERVER *altered)
{
  DBUG_ENTER("prepare_server_struct_for_update");

  altered->server_name= strdup_root(&mem, server_options->server_name);
  altered->server_name_length= server_options->server_name_length;
  DBUG_PRINT("info", ("existing name %s altered name %s",
                      existing->server_name, altered->server_name));

  /*
    The logic here is this: is this value set AND is it different
    than the existing value?
  */
  altered->host=
    (server_options->host && (strcmp(server_options->host, existing->host))) ?
     strdup_root(&mem, server_options->host) : 0;

  altered->db=
      (server_options->db && (strcmp(server_options->db, existing->db))) ?
        strdup_root(&mem, server_options->db) : 0;

  altered->username=
      (server_options->username &&
      (strcmp(server_options->username, existing->username))) ?
        strdup_root(&mem, server_options->username) : 0;

  altered->password=
      (server_options->password &&
      (strcmp(server_options->password, existing->password))) ?
        strdup_root(&mem, server_options->password) : 0;

  /*
    port is initialised to -1, so if unset, it will be -1
  */
  altered->port= (server_options->port > -1 &&
                 server_options->port != existing->port) ?
    server_options->port : -1;

  altered->socket=
    (server_options->socket &&
    (strcmp(server_options->socket, existing->socket))) ?
      strdup_root(&mem, server_options->socket) : 0;

  altered->scheme=
    (server_options->scheme &&
    (strcmp(server_options->scheme, existing->scheme))) ?
      strdup_root(&mem, server_options->scheme) : 0;

  altered->owner=
    (server_options->owner &&
    (strcmp(server_options->owner, existing->owner))) ?
      strdup_root(&mem, server_options->owner) : 0;

  DBUG_VOID_RETURN;
}

/*

  SYNOPSIS
    servers_free()
      bool end

  NOTES

  RETURN VALUE
    void

*/

void servers_free(bool end)
{
  DBUG_ENTER("servers_free");
  if (!my_hash_inited(&servers_cache))
    DBUG_VOID_RETURN;
  if (!end)
  {
    free_root(&mem, MYF(MY_MARK_BLOCKS_FREE));
	my_hash_reset(&servers_cache);
    DBUG_VOID_RETURN;
  }
  rwlock_destroy(&THR_LOCK_servers);
  free_root(&mem,MYF(0));
  my_hash_free(&servers_cache);
  DBUG_VOID_RETURN;
}


/*
  SYNOPSIS

  clone_server(MEM_ROOT *mem_root, FOREIGN_SERVER *orig, FOREIGN_SERVER *buff)

  Create a clone of FOREIGN_SERVER. If the supplied mem_root is of
  thd->mem_root then the copy is automatically disposed at end of statement.

  NOTES

  ARGS
   MEM_ROOT pointer (strings are copied into this mem root) 
   FOREIGN_SERVER pointer (made a copy of)
   FOREIGN_SERVER buffer (if not-NULL, this pointer is returned)

  RETURN VALUE
   FOREIGN_SEVER pointer (copy of one supplied FOREIGN_SERVER)
*/

static FOREIGN_SERVER *clone_server(MEM_ROOT *mem, const FOREIGN_SERVER *server,
                                    FOREIGN_SERVER *buffer)
{
  DBUG_ENTER("sql_server.cc:clone_server");

  if (!buffer)
    buffer= (FOREIGN_SERVER *) alloc_root(mem, sizeof(FOREIGN_SERVER));

  buffer->server_name= strmake_root(mem, server->server_name,
                                    server->server_name_length);
  buffer->port= server->port;
  buffer->server_name_length= server->server_name_length;
  
  /* TODO: We need to examine which of these can really be NULL */
  buffer->db= server->db ? strdup_root(mem, server->db) : NULL;
  buffer->scheme= server->scheme ? strdup_root(mem, server->scheme) : NULL;
  buffer->username= server->username? strdup_root(mem, server->username): NULL;
  buffer->password= server->password? strdup_root(mem, server->password): NULL;
  buffer->socket= server->socket ? strdup_root(mem, server->socket) : NULL;
  buffer->owner= server->owner ? strdup_root(mem, server->owner) : NULL;
  buffer->host= server->host ? strdup_root(mem, server->host) : NULL;

 DBUG_RETURN(buffer);
}


/*

  SYNOPSIS
    get_server_by_name()
      const char *server_name

  NOTES

  RETURN VALUE
   FOREIGN_SERVER *

*/

FOREIGN_SERVER *get_server_by_name(MEM_ROOT *mem, const char *server_name,
                                   FOREIGN_SERVER *buff)
{
  size_t server_name_length;
  FOREIGN_SERVER *server;
  DBUG_ENTER("get_server_by_name");
  DBUG_PRINT("info", ("server_name %s", server_name));

  server_name_length= strlen(server_name);

  if (! server_name || !strlen(server_name))
  {
    DBUG_PRINT("info", ("server_name not defined!"));
    DBUG_RETURN((FOREIGN_SERVER *)NULL);
  }

  DBUG_PRINT("info", ("locking servers_cache"));
  rw_rdlock(&THR_LOCK_servers);
  if (!(server= (FOREIGN_SERVER *) my_hash_search(&servers_cache,
                                                  (uchar*) server_name,
                                                  server_name_length)))
  {
    DBUG_PRINT("info", ("server_name %s length %u not found!",
                        server_name, (unsigned) server_name_length));
    server= (FOREIGN_SERVER *) NULL;
  }
  /* otherwise, make copy of server */
  else
    server= clone_server(mem, server, buff);

  DBUG_PRINT("info", ("unlocking servers_cache"));
  rw_unlock(&THR_LOCK_servers);
  DBUG_RETURN(server);

}