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         struct ovsdb_error *error;
 107
 108         if (params->type != JSON_ARRAY) {
 109             error = ovsdb_syntax_error(params, NULL, "array expected");
 110         } else {
 111             error = ovsdb_syntax_error(params, NULL, "database name expected "
 112                                        "as first parameter");
 113         }
 114
 115         results = ovsdb_error_to_json(error);
 116         ovsdb_error_destroy(error);
 117         return results;
 118     }
 119
 120     x.db = db;
 121     x.txn = ovsdb_txn_create(db);
 122     x.symtab = ovsdb_symbol_table_create();
 123     x.durable = false;
 124     x.elapsed_msec = elapsed_msec;
 125     x.timeout_msec = LLONG_MAX;
 126     results = NULL;
 127
 128     results = json_array_create_empty();
 129     n_operations = params->u.array.n - 1;
 130     error = NULL;
 131     for (i = 1; i <= n_operations; i++) {
 132         struct json *operation = params->u.array.elems[i];
 133         struct ovsdb_error *parse_error;
 134         struct ovsdb_parser parser;
 135         struct json *result;
 136         const struct json *op;
 137
 138         /* Parse and execute operation. */
 139         ovsdb_parser_init(&parser, operation,
 140                           "ovsdb operation %zu of %zu", i + 1, n_operations);
 141         op = ovsdb_parser_member(&parser, "op", OP_ID);
 142         result = json_object_create();
 143         if (op) {
 144             const char *op_name = json_string(op);
 145             ovsdb_operation_executor *executor = lookup_executor(op_name);
 146             if (executor) {
 147                 error = executor(&x, &parser, result);
 148             } else {
 149                 ovsdb_parser_raise_error(&parser, "No operation \"%s\"",
 150                                          op_name);
 151             }
 152         } else {
 153             assert(ovsdb_parser_has_error(&parser));
 154         }
 155
 156         /* A parse error overrides any other error.
 157          * An error overrides any other result. */
 158         parse_error = ovsdb_parser_finish(&parser);
 159         if (parse_error) {
 160             ovsdb_error_destroy(error);
 161             error = parse_error;
 162         }
 163         if (error) {
 164             json_destroy(result);
 165             result = ovsdb_error_to_json(error);
 166         }
 167         if (error && !strcmp(ovsdb_error_get_tag(error), "not supported")
 168             && timeout_msec) {
 169             ovsdb_txn_abort(x.txn);
 170             *timeout_msec = x.timeout_msec;
 171
 172             json_destroy(result);
 173             json_destroy(results);
 174             results = NULL;
 175             goto exit;
 176         }
 177
 178         /* Add result to array. */
 179         json_array_add(results, result);
 180         if (error) {
 181             break;
 182         }
 183     }
 184
 185     if (!error) {
 186         error = ovsdb_txn_commit(x.txn, x.durable);
 187         if (error) {
 188             json_array_add(results, ovsdb_error_to_json(error));
 189         }
 190     } else {
 191         ovsdb_txn_abort(x.txn);
 192     }
 193
 194     while (json_array(results)->n < n_operations) {
 195         json_array_add(results, json_null_create());
 196     }
 197
 198 exit:
 199     ovsdb_error_destroy(error);
 200     ovsdb_symbol_table_destroy(x.symtab);
 201
 202     return results;
 203 }
 204
 205 struct ovsdb_error *
 206 ovsdb_execute_commit(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 207                      struct json *result OVS_UNUSED)
 208 {
 209     const struct json *durable;
 210
 211     durable = ovsdb_parser_member(parser, "durable", OP_BOOLEAN);
 212     if (durable && json_boolean(durable)) {
 213         x->durable = true;
 214     }
 215     return NULL;
 216 }
 217
 218 static struct ovsdb_error *
 219 ovsdb_execute_abort(struct ovsdb_execution *x OVS_UNUSED,
 220                     struct ovsdb_parser *parser OVS_UNUSED,
 221                     struct json *result OVS_UNUSED)
 222 {
 223     return ovsdb_error("aborted", "aborted by request");
 224 }
 225
 226 static struct ovsdb_table *
 227 parse_table(struct ovsdb_execution *x,
 228             struct ovsdb_parser *parser, const char *member)
 229 {
 230     struct ovsdb_table *table;
 231     const char *table_name;
 232     const struct json *json;
 233
 234     json = ovsdb_parser_member(parser, member, OP_ID);
 235     if (!json) {
 236         return NULL;
 237     }
 238     table_name = json_string(json);
 239
 240     table = shash_find_data(&x->db->tables, table_name);
 241     if (!table) {
 242         ovsdb_parser_raise_error(parser, "No table named %s.", table_name);
 243     }
 244     return table;
 245 }
 246
 247 static WARN_UNUSED_RESULT struct ovsdb_error *
 248 parse_row(struct ovsdb_parser *parser, const char *member,
 249           const struct ovsdb_table *table,
 250           struct ovsdb_symbol_table *symtab,
 251           struct ovsdb_row **rowp, struct ovsdb_column_set *columns)
 252 {
 253     struct ovsdb_error *error;
 254     const struct json *json;
 255     struct ovsdb_row *row;
 256
 257     *rowp = NULL;
 258
 259     if (!table) {
 260         return OVSDB_BUG("null table");
 261     }
 262     json = ovsdb_parser_member(parser, member, OP_OBJECT);
 263     if (!json) {
 264         return OVSDB_BUG("null row member");
 265     }
 266
 267     row = ovsdb_row_create(table);
 268     error = ovsdb_row_from_json(row, json, symtab, columns);
 269     if (error) {
 270         ovsdb_row_destroy(row);
 271         return error;
 272     } else {
 273         *rowp = row;
 274         return NULL;
 275     }
 276 }
 277
 278 struct ovsdb_error *
 279 ovsdb_execute_insert(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 280                      struct json *result)
 281 {
 282     struct ovsdb_table *table;
 283     struct ovsdb_row *row = NULL;
 284     const struct json *uuid_name;
 285     struct ovsdb_error *error;
 286     struct uuid row_uuid;
 287
 288     table = parse_table(x, parser, "table");
 289     uuid_name = ovsdb_parser_member(parser, "uuid-name", OP_ID | OP_OPTIONAL);
 290     error = ovsdb_parser_get_error(parser);
 291
 292     if (uuid_name) {
 293         struct ovsdb_symbol *symbol;
 294
 295         symbol = ovsdb_symbol_table_insert(x->symtab, json_string(uuid_name));
 296         if (symbol->used) {
 297             return ovsdb_syntax_error(uuid_name, "duplicate uuid-name",
 298                                       "This \"uuid-name\" appeared on an "
 299                                       "earlier \"insert\" operation.");
 300         }
 301         row_uuid = symbol->uuid;
 302         symbol->used = true;
 303     } else {
 304         uuid_generate(&row_uuid);
 305     }
 306
 307     if (!error) {
 308         error = parse_row(parser, "row", table, x->symtab, &row, NULL);
 309     }
 310     if (!error) {
 311         /* Check constraints for columns not included in "row", in case the
 312          * default values do not satisfy the constraints.  We could check only
 313          * the columns that have their default values by supplying an
 314          * ovsdb_column_set to parse_row() above, but I suspect that this is
 315          * cheaper.  */
 316         const struct shash_node *node;
 317
 318         SHASH_FOR_EACH (node, &table->schema->columns) {
 319             const struct ovsdb_column *column = node->data;
 320             const struct ovsdb_datum *datum = &row->fields[column->index];
 321
 322             /* If there are 0 keys or pairs, there's nothing to check.
 323              * If there is 1, it might be a default value.
 324              * If there are more, it can't be a default value, so the value has
 325              * already been checked. */
 326             if (datum->n == 1) {
 327                 error = ovsdb_datum_check_constraints(datum, &column->type);
 328                 if (error) {
 329                     ovsdb_row_destroy(row);
 330                     break;
 331                 }
 332             }
 333         }
 334     }
 335     if (!error) {
 336         *ovsdb_row_get_uuid_rw(row) = row_uuid;
 337         ovsdb_txn_row_insert(x->txn, row);
 338         json_object_put(result, "uuid",
 339                         ovsdb_datum_to_json(&row->fields[OVSDB_COL_UUID],
 340                                             &ovsdb_type_uuid));
 341     }
 342     return error;
 343 }
 344
 345 struct ovsdb_error *
 346 ovsdb_execute_select(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 347                      struct json *result)
 348 {
 349     struct ovsdb_table *table;
 350     const struct json *where, *columns_json, *sort_json;
 351     struct ovsdb_condition condition = OVSDB_CONDITION_INITIALIZER;
 352     struct ovsdb_column_set columns = OVSDB_COLUMN_SET_INITIALIZER;
 353     struct ovsdb_column_set sort = OVSDB_COLUMN_SET_INITIALIZER;
 354     struct ovsdb_error *error;
 355
 356     table = parse_table(x, parser, "table");
 357     where = ovsdb_parser_member(parser, "where", OP_ARRAY);
 358     columns_json = ovsdb_parser_member(parser, "columns",
 359                                        OP_ARRAY | OP_OPTIONAL);
 360     sort_json = ovsdb_parser_member(parser, "sort", OP_ARRAY | OP_OPTIONAL);
 361
 362     error = ovsdb_parser_get_error(parser);
 363     if (!error) {
 364         error = ovsdb_condition_from_json(table->schema, where, x->symtab,
 365                                           &condition);
 366     }
 367     if (!error) {
 368         error = ovsdb_column_set_from_json(columns_json, table, &columns);
 369     }
 370     if (!error) {
 371         error = ovsdb_column_set_from_json(sort_json, table, &sort);
 372     }
 373     if (!error) {
 374         struct ovsdb_row_set rows = OVSDB_ROW_SET_INITIALIZER;
 375
 376         ovsdb_query_distinct(table, &condition, &columns, &rows);
 377         ovsdb_row_set_sort(&rows, &sort);
 378         json_object_put(result, "rows",
 379                         ovsdb_row_set_to_json(&rows, &columns));
 380
 381         ovsdb_row_set_destroy(&rows);
 382     }
 383
 384     ovsdb_column_set_destroy(&columns);
 385     ovsdb_column_set_destroy(&sort);
 386     ovsdb_condition_destroy(&condition);
 387
 388     return error;
 389 }
 390
 391 struct update_row_cbdata {
 392     size_t n_matches;
 393     struct ovsdb_txn *txn;
 394     const struct ovsdb_row *row;
 395     const struct ovsdb_column_set *columns;
 396 };
 397
 398 static bool
 399 update_row_cb(const struct ovsdb_row *row, void *ur_)
 400 {
 401     struct update_row_cbdata *ur = ur_;
 402
 403     ur->n_matches++;
 404     if (!ovsdb_row_equal_columns(row, ur->row, ur->columns)) {
 405         ovsdb_row_update_columns(ovsdb_txn_row_modify(ur->txn, row),
 406                                  ur->row, ur->columns);
 407     }
 408
 409     return true;
 410 }
 411
 412 struct ovsdb_error *
 413 ovsdb_execute_update(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 414                      struct json *result)
 415 {
 416     struct ovsdb_table *table;
 417     const struct json *where;
 418     struct ovsdb_condition condition = OVSDB_CONDITION_INITIALIZER;
 419     struct ovsdb_column_set columns = OVSDB_COLUMN_SET_INITIALIZER;
 420     struct ovsdb_row *row = NULL;
 421     struct update_row_cbdata ur;
 422     struct ovsdb_error *error;
 423
 424     table = parse_table(x, parser, "table");
 425     where = ovsdb_parser_member(parser, "where", OP_ARRAY);
 426     error = ovsdb_parser_get_error(parser);
 427     if (!error) {
 428         error = parse_row(parser, "row", table, x->symtab, &row, &columns);
 429     }
 430     if (!error) {
 431         error = ovsdb_condition_from_json(table->schema, where, x->symtab,
 432                                           &condition);
 433     }
 434     if (!error) {
 435         ur.n_matches = 0;
 436         ur.txn = x->txn;
 437         ur.row = row;
 438         ur.columns = &columns;
 439         ovsdb_query(table, &condition, update_row_cb, &ur);
 440         json_object_put(result, "count", json_integer_create(ur.n_matches));
 441     }
 442
 443     ovsdb_row_destroy(row);
 444     ovsdb_column_set_destroy(&columns);
 445     ovsdb_condition_destroy(&condition);
 446
 447     return error;
 448 }
 449
 450 struct mutate_row_cbdata {
 451     size_t n_matches;
 452     struct ovsdb_txn *txn;
 453     const struct ovsdb_mutation_set *mutations;
 454 };
 455
 456 static bool
 457 mutate_row_cb(const struct ovsdb_row *row, void *mr_)
 458 {
 459     struct mutate_row_cbdata *mr = mr_;
 460
 461     mr->n_matches++;
 462     ovsdb_mutation_set_execute(ovsdb_txn_row_modify(mr->txn, row),
 463                                mr->mutations);
 464
 465     return true;
 466 }
 467
 468 struct ovsdb_error *
 469 ovsdb_execute_mutate(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 470                      struct json *result)
 471 {
 472     struct ovsdb_table *table;
 473     const struct json *where;
 474     const struct json *mutations_json;
 475     struct ovsdb_condition condition = OVSDB_CONDITION_INITIALIZER;
 476     struct ovsdb_mutation_set mutations = OVSDB_MUTATION_SET_INITIALIZER;
 477     struct ovsdb_row *row = NULL;
 478     struct mutate_row_cbdata mr;
 479     struct ovsdb_error *error;
 480
 481     table = parse_table(x, parser, "table");
 482     where = ovsdb_parser_member(parser, "where", OP_ARRAY);
 483     mutations_json = ovsdb_parser_member(parser, "mutations", OP_ARRAY);
 484     error = ovsdb_parser_get_error(parser);
 485     if (!error) {
 486         error = ovsdb_mutation_set_from_json(table->schema, mutations_json,
 487                                              x->symtab, &mutations);
 488     }
 489     if (!error) {
 490         error = ovsdb_condition_from_json(table->schema, where, x->symtab,
 491                                           &condition);
 492     }
 493     if (!error) {
 494         mr.n_matches = 0;
 495         mr.txn = x->txn;
 496         mr.mutations = &mutations;
 497         ovsdb_query(table, &condition, mutate_row_cb, &mr);
 498         json_object_put(result, "count", json_integer_create(mr.n_matches));
 499     }
 500
 501     ovsdb_row_destroy(row);
 502     ovsdb_mutation_set_destroy(&mutations);
 503     ovsdb_condition_destroy(&condition);
 504
 505     return error;
 506 }
 507
 508 struct delete_row_cbdata {
 509     size_t n_matches;
 510     const struct ovsdb_table *table;
 511     struct ovsdb_txn *txn;
 512 };
 513
 514 static bool
 515 delete_row_cb(const struct ovsdb_row *row, void *dr_)
 516 {
 517     struct delete_row_cbdata *dr = dr_;
 518
 519     dr->n_matches++;
 520     ovsdb_txn_row_delete(dr->txn, row);
 521
 522     return true;
 523 }
 524
 525 struct ovsdb_error *
 526 ovsdb_execute_delete(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 527                      struct json *result)
 528 {
 529     struct ovsdb_table *table;
 530     const struct json *where;
 531     struct ovsdb_condition condition = OVSDB_CONDITION_INITIALIZER;
 532     struct ovsdb_error *error;
 533
 534     where = ovsdb_parser_member(parser, "where", OP_ARRAY);
 535     table = parse_table(x, parser, "table");
 536     error = ovsdb_parser_get_error(parser);
 537     if (!error) {
 538         error = ovsdb_condition_from_json(table->schema, where, x->symtab,
 539                                           &condition);
 540     }
 541     if (!error) {
 542         struct delete_row_cbdata dr;
 543
 544         dr.n_matches = 0;
 545         dr.table = table;
 546         dr.txn = x->txn;
 547         ovsdb_query(table, &condition, delete_row_cb, &dr);
 548
 549         json_object_put(result, "count", json_integer_create(dr.n_matches));
 550     }
 551
 552     ovsdb_condition_destroy(&condition);
 553
 554     return error;
 555 }
 556
 557 struct wait_auxdata {
 558     struct ovsdb_row_hash *actual;
 559     struct ovsdb_row_hash *expected;
 560     bool *equal;
 561 };
 562
 563 static bool
 564 ovsdb_execute_wait_query_cb(const struct ovsdb_row *row, void *aux_)
 565 {
 566     struct wait_auxdata *aux = aux_;
 567
 568     if (ovsdb_row_hash_contains(aux->expected, row)) {
 569         ovsdb_row_hash_insert(aux->actual, row);
 570         return true;
 571     } else {
 572         /* The query row isn't in the expected result set, so the actual and
 573          * expected results sets definitely differ and we can short-circuit the
 574          * rest of the query. */
 575         *aux->equal = false;
 576         return false;
 577     }
 578 }
 579
 580 static struct ovsdb_error *
 581 ovsdb_execute_wait(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 582                    struct json *result OVS_UNUSED)
 583 {
 584     struct ovsdb_table *table;
 585     const struct json *timeout, *where, *columns_json, *until, *rows;
 586     struct ovsdb_condition condition = OVSDB_CONDITION_INITIALIZER;
 587     struct ovsdb_column_set columns = OVSDB_COLUMN_SET_INITIALIZER;
 588     struct ovsdb_row_hash expected = OVSDB_ROW_HASH_INITIALIZER(expected);
 589     struct ovsdb_row_hash actual = OVSDB_ROW_HASH_INITIALIZER(actual);
 590     struct ovsdb_error *error;
 591     struct wait_auxdata aux;
 592     long long int timeout_msec = 0;
 593     size_t i;
 594
 595     timeout = ovsdb_parser_member(parser, "timeout", OP_NUMBER | OP_OPTIONAL);
 596     where = ovsdb_parser_member(parser, "where", OP_ARRAY);
 597     columns_json = ovsdb_parser_member(parser, "columns",
 598                                        OP_ARRAY | OP_OPTIONAL);
 599     until = ovsdb_parser_member(parser, "until", OP_STRING);
 600     rows = ovsdb_parser_member(parser, "rows", OP_ARRAY);
 601     table = parse_table(x, parser, "table");
 602     error = ovsdb_parser_get_error(parser);
 603     if (!error) {
 604         error = ovsdb_condition_from_json(table->schema, where, x->symtab,
 605                                           &condition);
 606     }
 607     if (!error) {
 608         error = ovsdb_column_set_from_json(columns_json, table, &columns);
 609     }
 610     if (!error) {
 611         if (timeout) {
 612             timeout_msec = MIN(LLONG_MAX, json_real(timeout));
 613             if (timeout_msec < 0) {
 614                 error = ovsdb_syntax_error(timeout, NULL,
 615                                            "timeout must be nonnegative");
 616             } else if (timeout_msec < x->timeout_msec) {
 617                 x->timeout_msec = timeout_msec;
 618             }
 619         } else {
 620             timeout_msec = LLONG_MAX;
 621         }
 622         if (strcmp(json_string(until), "==")
 623             && strcmp(json_string(until), "!=")) {
 624             error = ovsdb_syntax_error(until, NULL,
 625                                        "\"until\" must be \"==\" or \"!=\"");
 626         }
 627     }
 628     if (!error) {
 629         /* Parse "rows" into 'expected'. */
 630         ovsdb_row_hash_init(&expected, &columns);
 631         for (i = 0; i < rows->u.array.n; i++) {
 632             struct ovsdb_error *error;
 633             struct ovsdb_row *row;
 634
 635             row = ovsdb_row_create(table);
 636             error = ovsdb_row_from_json(row, rows->u.array.elems[i], x->symtab,
 637                                         NULL);
 638             if (error) {
 639                 break;
 640             }
 641
 642             if (!ovsdb_row_hash_insert(&expected, row)) {
 643                 /* XXX Perhaps we should abort with an error or log a
 644                  * warning. */
 645                 ovsdb_row_destroy(row);
 646             }
 647         }
 648     }
 649     if (!error) {
 650         /* Execute query. */
 651         bool equal = true;
 652         ovsdb_row_hash_init(&actual, &columns);
 653         aux.actual = &actual;
 654         aux.expected = &expected;
 655         aux.equal = &equal;
 656         ovsdb_query(table, &condition, ovsdb_execute_wait_query_cb, &aux);
 657         if (equal) {
 658             /* We know that every row in 'actual' is also in 'expected'.  We
 659              * also know that all of the rows in 'actual' are distinct and that
 660              * all of the rows in 'expected' are distinct.  Therefore, if
 661              * 'actual' and 'expected' have the same number of rows, then they
 662              * have the same content. */
 663             size_t n_actual = ovsdb_row_hash_count(&actual);
 664             size_t n_expected = ovsdb_row_hash_count(&expected);
 665             equal = n_actual == n_expected;
 666         }
 667         if (!strcmp(json_string(until), "==") != equal) {
 668             if (timeout && x->elapsed_msec >= timeout_msec) {
 669                 if (x->elapsed_msec) {
 670                     error = ovsdb_error("timed out",
 671                                         "\"wait\" timed out after %lld ms",
 672                                         x->elapsed_msec);
 673                 } else {
 674                     error = ovsdb_error("timed out", "\"wait\" timed out");
 675                 }
 676             } else {
 677                 /* ovsdb_execute() will change this, if triggers really are
 678                  * supported. */
 679                 error = ovsdb_error("not supported", "triggers not supported");
 680             }
 681         }
 682     }
 683
 684
 685     ovsdb_row_hash_destroy(&expected, true);
 686     ovsdb_row_hash_destroy(&actual, false);
 687     ovsdb_column_set_destroy(&columns);
 688     ovsdb_condition_destroy(&condition);
 689
 690     return error;
 691 }
 692
 693 static struct ovsdb_error *
 694 ovsdb_execute_comment(struct ovsdb_execution *x, struct ovsdb_parser *parser,
 695                       struct json *result OVS_UNUSED)
 696 {
 697     const struct json *comment;
 698
 699     comment = ovsdb_parser_member(parser, "comment", OP_STRING);
 700     if (!comment) {
 701         return NULL;
 702     }
 703     ovsdb_txn_add_comment(x->txn, json_string(comment));
 704
 705     return NULL;
 706 }