ovsdb/execution.c

   1 /* Copyright (c) 2009, 2010 Nicira Networks
   2  *
   3  * Licensed under the Apache License, Version 2.0 (the "License");
   4  * you may not use this file except in compliance with the License.
   5  * You may obtain a copy of the License at:
   6  *
   7  *     http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  * Unless required by applicable law or agreed to in writing, software
  10  * distributed under the License is distributed on an "AS IS" BASIS,
  11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12  * See the License for the specific language governing permissions and
  13  * limitations under the License.
  14  */
  15
  16 #include <config.h>
  17
  18 #include <assert.h>
  19 #include <limits.h>
  20
  21 #include "column.h"
  22 #include "condition.h"
  23 #include "file.h"
  24 #include "json.h"
  25 #include "mutation.h"
  26 #include "ovsdb-data.h"
  27 #include "ovsdb-error.h"
  28 #include "ovsdb-parser.h"
  29 #include "ovsdb.h"
  30 #include "query.h"
  31 #include "row.h"
  32 #include "table.h"
  33 #include "timeval.h"
  34 #include "transaction.h"
  35
  36 struct ovsdb_execution {
  37     struct ovsdb *db;
  38     struct ovsdb_txn *txn;
  39     struct ovsdb_symbol_table *symtab;
  40     bool durable;
  41
  42     /* Triggers. */
  43     long long int elapsed_msec;
  44     long long int timeout_msec;
  45 };
  46
  47 typedef struct ovsdb_error *ovsdb_operation_executor(struct ovsdb_execution *,
  48                                                      struct ovsdb_parser *,
  49                                                      struct json *result);
  50
  51 static ovsdb_operation_executor ovsdb_execute_insert;
  52 static ovsdb_operation_executor ovsdb_execute_select;
  53 static ovsdb_operation_executor ovsdb_execute_update;
  54 static ovsdb_operation_executor ovsdb_execute_mutate;
  55 static ovsdb_operation_executor ovsdb_execute_delete;
  56 static ovsdb_operation_executor ovsdb_execute_wait;
  57 static ovsdb_operation_executor ovsdb_execute_commit;
  58 static ovsdb_operation_executor ovsdb_execute_abort;
  59 static ovsdb_operation_executor ovsdb_execute_comment;
  60
  61 static ovsdb_operation_executor *
  62 lookup_executor(const char *name)
  63 {
  64     struct ovsdb_operation {
  65         const char *name;
  66         ovsdb_operation_executor *executor;
  67     };
  68
  69     static const struct ovsdb_operation operations[] = {
  70         { "insert", ovsdb_execute_insert },
  71         { "select", ovsdb_execute_select },
  72         { "update", ovsdb_execute_update },
  73         { "mutate", ovsdb_execute_mutate },
  74         { "delete", ovsdb_execute_delete },
  75         { "wait", ovsdb_execute_wait },
  76         { "commit", ovsdb_execute_commit },
  77         { "abort", ovsdb_execute_abort },
  78         { "comment", ovsdb_execute_comment },
  79     };
  80
  81     size_t i;
  82
  83     for (i = 0; i < ARRAY_SIZE(operations); i++) {
  84         const struct ovsdb_operation *c = &operations[i];
  85         if (!strcmp(c->name, name)) {
  86             return c->executor;
  87         }
  88     }
  89     return NULL;
  90 }
  91
  92 struct json *
  93 ovsdb_execute(struct ovsdb *db, const struct json *params,
  94               long long int elapsed_msec, long long int *timeout_msec)
  95 {
  96     struct ovsdb_execution x;
  97     struct ovsdb_error *error;
  98     struct json *results;
  99     size_t n_operations;
 100     size_t i;
 101
 102     if (params->type != JSON_ARRAY
 103         || !params->u.array.n
 104         || params->u.array.elems[0]->type != JSON_STRING
 105         || strcmp(params->u.array.elems[0]->u.string, db->schema->name)) {
 106         if (params->type != JSON_ARRAY) {
 107             error = ovsdb_syntax_error(params, NULL, "array expected");
 108         } else {
 109             error = ovsdb_syntax_error(params, NULL, "database name expected "
 110                                        "as first parameter");
 111         }
 112
 113         results = ovsdb_error_to_json(error);
 114         ovsdb_error_destroy(error);
 115         return results;
 116     }
 117
 118     x.db = db;
 119     x.txn = ovsdb_txn_create(db);
 120     x.symtab = ovsdb_symbol_table_create();
 121     x.durable = false;
 122     x.elapsed_msec = elapsed_msec;
 123     x.timeout_msec = LLONG_MAX;
 124     results = NULL;
 125
 126     results = json_array_create_empty();
 127     n_operations = params->u.array.n - 1;
 128     error = NULL;
 129     for (i = 1; i <= n_operations; i++) {
 130         struct json *operation = params->u.array.elems[i];
 131         struct ovsdb_error *parse_error;
 132         struct ovsdb_parser parser;
 133         struct json *result;
 134         const struct json *op;
 135
 136         /* Parse and execute operation. */
 137         ovsdb_parser_init(&parser, operation,
 138                           "ovsdb operation %zu of %zu", i, n_operations);
 139         op = ovsdb_parser_member(&parser, "op", OP_ID);
 140         result = json_object_create();
 141         if (op) {
 142             const char *op_name = json_string(op);
 143             ovsdb_operation_executor *executor = lookup_executor(op_name);
 144             if (executor) {
 145                 error = executor(&x, &parser, result);
 146             } else {
 147                 ovsdb_parser_raise_error(&parser, "No operation \"%s\"",
 148                                          op_name);
 149             }
 150         } else {
 151             assert(ovsdb_parser_has_error(&parser));
 152         }
 153
 154         /* A parse error overrides any other error.
 155          * An error overrides any other result. */
 156         parse_error = ovsdb_parser_finish(&parser);
 157         if (parse_error) {
 158             ovsdb_error_destroy(error);
 159             error = parse_error;
 160         }
 161         if (error) {
 162             json_destroy(result);
 163             result = ovsdb_error_to_json(error);
 164         }
 165         if (error && !strcmp(ovsdb_error_get_tag(error), "not supported")
 166             && timeout_msec) {
 167             ovsdb_txn_abort(x.txn);
 168             *timeout_msec = x.timeout_msec;
 169
 170             json_destroy(result);
 171             json_destroy(results);
 172             results = NULL;
 173             goto exit;
 174         }
 175
 176         /* Add result to array. */
 177         json_array_add(results, result);
 178         if (error) {
 179             break;
 180         }
 181     }
 182
 183     if (!error) {
 184         error = ovsdb_txn_commit(x.txn, x.durable);
 185         if (error) {
 186             json_array_add(results, ovsdb_error_to_json(error));
 187         }
 188     } else {
 189         ovsdb_txn_abort(x.txn);
 190     }
 191
 192     while (json_array(results)->n < n_operations) {
 193         json_array_add(results, json_null_create());
 194     }
 195
 196 exit:
 197     ovsdb_error_destroy(error);
 198     ovsdb_symbol_table_destroy(x.symtab);
 199
 200     return results;
 201 }
 202
 203 struct ovsdb_error *
 204 ovsdb_execute_commit(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 205                      struct json *result OVS_UNUSED)
 206 {
 207     const struct json *durable;
 208
 209     durable = ovsdb_parser_member(parser, "durable", OP_BOOLEAN);
 210     if (durable && json_boolean(durable)) {
 211         x->durable = true;
 212     }
 213     return NULL;
 214 }
 215
 216 static struct ovsdb_error *
 217 ovsdb_execute_abort(struct ovsdb_execution *x OVS_UNUSED,
 218                     struct ovsdb_parser *parser OVS_UNUSED,
 219                     struct json *result OVS_UNUSED)
 220 {
 221     return ovsdb_error("aborted", "aborted by request");
 222 }
 223
 224 static struct ovsdb_table *
 225 parse_table(struct ovsdb_execution *x,
 226             struct ovsdb_parser *parser, const char *member)
 227 {
 228     struct ovsdb_table *table;
 229     const char *table_name;
 230     const struct json *json;
 231
 232     json = ovsdb_parser_member(parser, member, OP_ID);
 233     if (!json) {
 234         return NULL;
 235     }
 236     table_name = json_string(json);
 237
 238     table = shash_find_data(&x->db->tables, table_name);
 239     if (!table) {
 240         ovsdb_parser_raise_error(parser, "No table named %s.", table_name);
 241     }
 242     return table;
 243 }
 244
 245 static WARN_UNUSED_RESULT struct ovsdb_error *
 246 parse_row(struct ovsdb_parser *parser, const char *member,
 247           const struct ovsdb_table *table,
 248           struct ovsdb_symbol_table *symtab,
 249           struct ovsdb_row **rowp, struct ovsdb_column_set *columns)
 250 {
 251     struct ovsdb_error *error;
 252     const struct json *json;
 253     struct ovsdb_row *row;
 254
 255     *rowp = NULL;
 256
 257     if (!table) {
 258         return OVSDB_BUG("null table");
 259     }
 260     json = ovsdb_parser_member(parser, member, OP_OBJECT);
 261     if (!json) {
 262         return OVSDB_BUG("null row member");
 263     }
 264
 265     row = ovsdb_row_create(table);
 266     error = ovsdb_row_from_json(row, json, symtab, columns);
 267     if (error) {
 268         ovsdb_row_destroy(row);
 269         return error;
 270     } else {
 271         *rowp = row;
 272         return NULL;
 273     }
 274 }
 275
 276 struct ovsdb_error *
 277 ovsdb_execute_insert(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 278                      struct json *result)
 279 {
 280     struct ovsdb_table *table;
 281     struct ovsdb_row *row = NULL;
 282     const struct json *uuid_name;
 283     struct ovsdb_error *error;
 284     struct uuid row_uuid;
 285
 286     table = parse_table(x, parser, "table");
 287     uuid_name = ovsdb_parser_member(parser, "uuid-name", OP_ID | OP_OPTIONAL);
 288     error = ovsdb_parser_get_error(parser);
 289
 290     if (uuid_name) {
 291         struct ovsdb_symbol *symbol;
 292
 293         symbol = ovsdb_symbol_table_insert(x->symtab, json_string(uuid_name));
 294         if (symbol->used) {
 295             return ovsdb_syntax_error(uuid_name, "duplicate uuid-name",
 296                                       "This \"uuid-name\" appeared on an "
 297                                       "earlier \"insert\" operation.");
 298         }
 299         row_uuid = symbol->uuid;
 300         symbol->used = true;
 301     } else {
 302         uuid_generate(&row_uuid);
 303     }
 304
 305     if (!error) {
 306         error = parse_row(parser, "row", table, x->symtab, &row, NULL);
 307     }
 308     if (!error) {
 309         /* Check constraints for columns not included in "row", in case the
 310          * default values do not satisfy the constraints.  We could check only
 311          * the columns that have their default values by supplying an
 312          * ovsdb_column_set to parse_row() above, but I suspect that this is
 313          * cheaper.  */
 314         const struct shash_node *node;
 315
 316         SHASH_FOR_EACH (node, &table->schema->columns) {
 317             const struct ovsdb_column *column = node->data;
 318             const struct ovsdb_datum *datum = &row->fields[column->index];
 319
 320             /* If there are 0 keys or pairs, there's nothing to check.
 321              * If there is 1, it might be a default value.
 322              * If there are more, it can't be a default value, so the value has
 323              * already been checked. */
 324             if (datum->n == 1) {
 325                 error = ovsdb_datum_check_constraints(datum, &column->type);
 326                 if (error) {
 327                     ovsdb_row_destroy(row);
 328                     break;
 329                 }
 330             }
 331         }
 332     }
 333     if (!error) {
 334         *ovsdb_row_get_uuid_rw(row) = row_uuid;
 335         ovsdb_txn_row_insert(x->txn, row);
 336         json_object_put(result, "uuid",
 337                         ovsdb_datum_to_json(&row->fields[OVSDB_COL_UUID],
 338                                             &ovsdb_type_uuid));
 339     }
 340     return error;
 341 }
 342
 343 struct ovsdb_error *
 344 ovsdb_execute_select(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 345                      struct json *result)
 346 {
 347     struct ovsdb_table *table;
 348     const struct json *where, *columns_json, *sort_json;
 349     struct ovsdb_condition condition = OVSDB_CONDITION_INITIALIZER;
 350     struct ovsdb_column_set columns = OVSDB_COLUMN_SET_INITIALIZER;
 351     struct ovsdb_column_set sort = OVSDB_COLUMN_SET_INITIALIZER;
 352     struct ovsdb_error *error;
 353
 354     table = parse_table(x, parser, "table");
 355     where = ovsdb_parser_member(parser, "where", OP_ARRAY);
 356     columns_json = ovsdb_parser_member(parser, "columns",
 357                                        OP_ARRAY | OP_OPTIONAL);
 358     sort_json = ovsdb_parser_member(parser, "sort", OP_ARRAY | OP_OPTIONAL);
 359
 360     error = ovsdb_parser_get_error(parser);
 361     if (!error) {
 362         error = ovsdb_condition_from_json(table->schema, where, x->symtab,
 363                                           &condition);
 364     }
 365     if (!error) {
 366         error = ovsdb_column_set_from_json(columns_json, table, &columns);
 367     }
 368     if (!error) {
 369         error = ovsdb_column_set_from_json(sort_json, table, &sort);
 370     }
 371     if (!error) {
 372         struct ovsdb_row_set rows = OVSDB_ROW_SET_INITIALIZER;
 373
 374         ovsdb_query_distinct(table, &condition, &columns, &rows);
 375         ovsdb_row_set_sort(&rows, &sort);
 376         json_object_put(result, "rows",
 377                         ovsdb_row_set_to_json(&rows, &columns));
 378
 379         ovsdb_row_set_destroy(&rows);
 380     }
 381
 382     ovsdb_column_set_destroy(&columns);
 383     ovsdb_column_set_destroy(&sort);
 384     ovsdb_condition_destroy(&condition);
 385
 386     return error;
 387 }
 388
 389 struct update_row_cbdata {
 390     size_t n_matches;
 391     struct ovsdb_txn *txn;
 392     const struct ovsdb_row *row;
 393     const struct ovsdb_column_set *columns;
 394 };
 395
 396 static bool
 397 update_row_cb(const struct ovsdb_row *row, void *ur_)
 398 {
 399     struct update_row_cbdata *ur = ur_;
 400
 401     ur->n_matches++;
 402     if (!ovsdb_row_equal_columns(row, ur->row, ur->columns)) {
 403         ovsdb_row_update_columns(ovsdb_txn_row_modify(ur->txn, row),
 404                                  ur->row, ur->columns);
 405     }
 406
 407     return true;
 408 }
 409
 410 struct ovsdb_error *
 411 ovsdb_execute_update(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 412                      struct json *result)
 413 {
 414     struct ovsdb_table *table;
 415     const struct json *where;
 416     struct ovsdb_condition condition = OVSDB_CONDITION_INITIALIZER;
 417     struct ovsdb_column_set columns = OVSDB_COLUMN_SET_INITIALIZER;
 418     struct ovsdb_row *row = NULL;
 419     struct update_row_cbdata ur;
 420     struct ovsdb_error *error;
 421
 422     table = parse_table(x, parser, "table");
 423     where = ovsdb_parser_member(parser, "where", OP_ARRAY);
 424     error = ovsdb_parser_get_error(parser);
 425     if (!error) {
 426         error = parse_row(parser, "row", table, x->symtab, &row, &columns);
 427     }
 428     if (!error) {
 429         error = ovsdb_condition_from_json(table->schema, where, x->symtab,
 430                                           &condition);
 431     }
 432     if (!error) {
 433         ur.n_matches = 0;
 434         ur.txn = x->txn;
 435         ur.row = row;
 436         ur.columns = &columns;
 437         ovsdb_query(table, &condition, update_row_cb, &ur);
 438         json_object_put(result, "count", json_integer_create(ur.n_matches));
 439     }
 440
 441     ovsdb_row_destroy(row);
 442     ovsdb_column_set_destroy(&columns);
 443     ovsdb_condition_destroy(&condition);
 444
 445     return error;
 446 }
 447
 448 struct mutate_row_cbdata {
 449     size_t n_matches;
 450     struct ovsdb_txn *txn;
 451     const struct ovsdb_mutation_set *mutations;
 452 };
 453
 454 static bool
 455 mutate_row_cb(const struct ovsdb_row *row, void *mr_)
 456 {
 457     struct mutate_row_cbdata *mr = mr_;
 458
 459     mr->n_matches++;
 460     ovsdb_mutation_set_execute(ovsdb_txn_row_modify(mr->txn, row),
 461                                mr->mutations);
 462
 463     return true;
 464 }
 465
 466 struct ovsdb_error *
 467 ovsdb_execute_mutate(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 468                      struct json *result)
 469 {
 470     struct ovsdb_table *table;
 471     const struct json *where;
 472     const struct json *mutations_json;
 473     struct ovsdb_condition condition = OVSDB_CONDITION_INITIALIZER;
 474     struct ovsdb_mutation_set mutations = OVSDB_MUTATION_SET_INITIALIZER;
 475     struct ovsdb_row *row = NULL;
 476     struct mutate_row_cbdata mr;
 477     struct ovsdb_error *error;
 478
 479     table = parse_table(x, parser, "table");
 480     where = ovsdb_parser_member(parser, "where", OP_ARRAY);
 481     mutations_json = ovsdb_parser_member(parser, "mutations", OP_ARRAY);
 482     error = ovsdb_parser_get_error(parser);
 483     if (!error) {
 484         error = ovsdb_mutation_set_from_json(table->schema, mutations_json,
 485                                              x->symtab, &mutations);
 486     }
 487     if (!error) {
 488         error = ovsdb_condition_from_json(table->schema, where, x->symtab,
 489                                           &condition);
 490     }
 491     if (!error) {
 492         mr.n_matches = 0;
 493         mr.txn = x->txn;
 494         mr.mutations = &mutations;
 495         ovsdb_query(table, &condition, mutate_row_cb, &mr);
 496         json_object_put(result, "count", json_integer_create(mr.n_matches));
 497     }
 498
 499     ovsdb_row_destroy(row);
 500     ovsdb_mutation_set_destroy(&mutations);
 501     ovsdb_condition_destroy(&condition);
 502
 503     return error;
 504 }
 505
 506 struct delete_row_cbdata {
 507     size_t n_matches;
 508     const struct ovsdb_table *table;
 509     struct ovsdb_txn *txn;
 510 };
 511
 512 static bool
 513 delete_row_cb(const struct ovsdb_row *row, void *dr_)
 514 {
 515     struct delete_row_cbdata *dr = dr_;
 516
 517     dr->n_matches++;
 518     ovsdb_txn_row_delete(dr->txn, row);
 519
 520     return true;
 521 }
 522
 523 struct ovsdb_error *
 524 ovsdb_execute_delete(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 525                      struct json *result)
 526 {
 527     struct ovsdb_table *table;
 528     const struct json *where;
 529     struct ovsdb_condition condition = OVSDB_CONDITION_INITIALIZER;
 530     struct ovsdb_error *error;
 531
 532     where = ovsdb_parser_member(parser, "where", OP_ARRAY);
 533     table = parse_table(x, parser, "table");
 534     error = ovsdb_parser_get_error(parser);
 535     if (!error) {
 536         error = ovsdb_condition_from_json(table->schema, where, x->symtab,
 537                                           &condition);
 538     }
 539     if (!error) {
 540         struct delete_row_cbdata dr;
 541
 542         dr.n_matches = 0;
 543         dr.table = table;
 544         dr.txn = x->txn;
 545         ovsdb_query(table, &condition, delete_row_cb, &dr);
 546
 547         json_object_put(result, "count", json_integer_create(dr.n_matches));
 548     }
 549
 550     ovsdb_condition_destroy(&condition);
 551
 552     return error;
 553 }
 554
 555 struct wait_auxdata {
 556     struct ovsdb_row_hash *actual;
 557     struct ovsdb_row_hash *expected;
 558     bool *equal;
 559 };
 560
 561 static bool
 562 ovsdb_execute_wait_query_cb(const struct ovsdb_row *row, void *aux_)
 563 {
 564     struct wait_auxdata *aux = aux_;
 565
 566     if (ovsdb_row_hash_contains(aux->expected, row)) {
 567         ovsdb_row_hash_insert(aux->actual, row);
 568         return true;
 569     } else {
 570         /* The query row isn't in the expected result set, so the actual and
 571          * expected results sets definitely differ and we can short-circuit the
 572          * rest of the query. */
 573         *aux->equal = false;
 574         return false;
 575     }
 576 }
 577
 578 static struct ovsdb_error *
 579 ovsdb_execute_wait(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 580                    struct json *result OVS_UNUSED)
 581 {
 582     struct ovsdb_table *table;
 583     const struct json *timeout, *where, *columns_json, *until, *rows;
 584     struct ovsdb_condition condition = OVSDB_CONDITION_INITIALIZER;
 585     struct ovsdb_column_set columns = OVSDB_COLUMN_SET_INITIALIZER;
 586     struct ovsdb_row_hash expected = OVSDB_ROW_HASH_INITIALIZER(expected);
 587     struct ovsdb_row_hash actual = OVSDB_ROW_HASH_INITIALIZER(actual);
 588     struct ovsdb_error *error;
 589     struct wait_auxdata aux;
 590     long long int timeout_msec = 0;
 591     size_t i;
 592
 593     timeout = ovsdb_parser_member(parser, "timeout", OP_NUMBER | OP_OPTIONAL);
 594     where = ovsdb_parser_member(parser, "where", OP_ARRAY);
 595     columns_json = ovsdb_parser_member(parser, "columns",
 596                                        OP_ARRAY | OP_OPTIONAL);
 597     until = ovsdb_parser_member(parser, "until", OP_STRING);
 598     rows = ovsdb_parser_member(parser, "rows", OP_ARRAY);
 599     table = parse_table(x, parser, "table");
 600     error = ovsdb_parser_get_error(parser);
 601     if (!error) {
 602         error = ovsdb_condition_from_json(table->schema, where, x->symtab,
 603                                           &condition);
 604     }
 605     if (!error) {
 606         error = ovsdb_column_set_from_json(columns_json, table, &columns);
 607     }
 608     if (!error) {
 609         if (timeout) {
 610             timeout_msec = MIN(LLONG_MAX, json_real(timeout));
 611             if (timeout_msec < 0) {
 612                 error = ovsdb_syntax_error(timeout, NULL,
 613                                            "timeout must be nonnegative");
 614             } else if (timeout_msec < x->timeout_msec) {
 615                 x->timeout_msec = timeout_msec;
 616             }
 617         } else {
 618             timeout_msec = LLONG_MAX;
 619         }
 620         if (strcmp(json_string(until), "==")
 621             && strcmp(json_string(until), "!=")) {
 622             error = ovsdb_syntax_error(until, NULL,
 623                                        "\"until\" must be \"==\" or \"!=\"");
 624         }
 625     }
 626     if (!error) {
 627         /* Parse "rows" into 'expected'. */
 628         ovsdb_row_hash_init(&expected, &columns);
 629         for (i = 0; i < rows->u.array.n; i++) {
 630             struct ovsdb_row *row;
 631
 632             row = ovsdb_row_create(table);
 633             error = ovsdb_row_from_json(row, rows->u.array.elems[i], x->symtab,
 634                                         NULL);
 635             if (error) {
 636                 break;
 637             }
 638
 639             if (!ovsdb_row_hash_insert(&expected, row)) {
 640                 /* XXX Perhaps we should abort with an error or log a
 641                  * warning. */
 642                 ovsdb_row_destroy(row);
 643             }
 644         }
 645     }
 646     if (!error) {
 647         /* Execute query. */
 648         bool equal = true;
 649         ovsdb_row_hash_init(&actual, &columns);
 650         aux.actual = &actual;
 651         aux.expected = &expected;
 652         aux.equal = &equal;
 653         ovsdb_query(table, &condition, ovsdb_execute_wait_query_cb, &aux);
 654         if (equal) {
 655             /* We know that every row in 'actual' is also in 'expected'.  We
 656              * also know that all of the rows in 'actual' are distinct and that
 657              * all of the rows in 'expected' are distinct.  Therefore, if
 658              * 'actual' and 'expected' have the same number of rows, then they
 659              * have the same content. */
 660             size_t n_actual = ovsdb_row_hash_count(&actual);
 661             size_t n_expected = ovsdb_row_hash_count(&expected);
 662             equal = n_actual == n_expected;
 663         }
 664         if (!strcmp(json_string(until), "==") != equal) {
 665             if (timeout && x->elapsed_msec >= timeout_msec) {
 666                 if (x->elapsed_msec) {
 667                     error = ovsdb_error("timed out",
 668                                         "\"wait\" timed out after %lld ms",
 669                                         x->elapsed_msec);
 670                 } else {
 671                     error = ovsdb_error("timed out", "\"wait\" timed out");
 672                 }
 673             } else {
 674                 /* ovsdb_execute() will change this, if triggers really are
 675                  * supported. */
 676                 error = ovsdb_error("not supported", "triggers not supported");
 677             }
 678         }
 679     }
 680
 681
 682     ovsdb_row_hash_destroy(&expected, true);
 683     ovsdb_row_hash_destroy(&actual, false);
 684     ovsdb_column_set_destroy(&columns);
 685     ovsdb_condition_destroy(&condition);
 686
 687     return error;
 688 }
 689
 690 static struct ovsdb_error *
 691 ovsdb_execute_comment(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 692                       struct json *result OVS_UNUSED)
 693 {
 694     const struct json *comment;
 695
 696     comment = ovsdb_parser_member(parser, "comment", OP_STRING);
 697     if (!comment) {
 698         return NULL;
 699     }
 700     ovsdb_txn_add_comment(x->txn, json_string(comment));
 701
 702     return NULL;
 703 }