mongoc_client_write_command_with_opts - Man Page

bool
mongoc_client_write_command_with_opts (mongoc_client_t *client,
                                       const char *db_name,
                                       const bson_t *command,
                                       const bson_t *opts,
                                       bson_t *reply,
                                       bson_error_t *error);

Execute a command on the server, applying logic that is specific to commands that write, and taking the MongoDB server version into account. To send a raw command to the server without any of this logic, use mongoc_client_command_simple().

Use this function for commands that write such as "drop" or "createRole" (but not for "insert", "update", or "delete", see Basic Write Operations). Write concern and collation can be overridden by various sources. In a transaction, read concern and write concern are prohibited in opts. The highest-priority sources for these options are listed first in the following table. The write concern is omitted for MongoDB before 3.4.

See the example for transactions and for the "distinct" command with opts.

reply is always initialized, and must be freed with bson_destroy().

• client: A mongoc_client_t.
• db_name: The name of the database to run the command on.
• command: A bson_t containing the command specification.
• opts: A bson_t containing additional options.
• reply: A maybe-NULL pointer to overwritable storage for a bson_t to contain the results.
• error: An optional location for a bson_error_t or NULL.

opts may be NULL or a BSON document with additional command options:

• writeConcern: Construct a mongoc_write_concern_t and use mongoc_write_concern_append() to add the write concern to opts. See the example code for mongoc_client_write_command_with_opts().
• sessionId: First, construct a mongoc_client_session_t with mongoc_client_start_session(). You can begin a transaction with mongoc_client_session_start_transaction(), optionally with a mongoc_transaction_opt_t that overrides the options inherited from client, and use mongoc_client_session_append() to add the session to opts. See the example code for mongoc_client_session_t.
• collation: Configure textual comparisons. See Setting Collation Order, and the MongoDB Manual entry on Collation. Collation requires MongoDB 3.2 or later, otherwise an error is returned.
• serverId: To target a specific server, include an int32 "serverId" field. Obtain the id by calling mongoc_client_select_server(), then mongoc_server_description_id() on its return value.

Consult the MongoDB Manual entry on Database Commands for each command's arguments.

Errors are propagated via the error parameter.

Returns true if successful. Returns false and sets error if there are invalid arguments or a server or network error.

A write concern timeout or write concern error is considered a failure.

Do not use this function to call the basic write commands "insert", "update", and "delete". Those commands require special logic not implemented in mongoc_client_write_command_with_opts. For basic write operations use CRUD functions such as mongoc_collection_insert_one() and the others described in the CRUD tutorial, or use the Bulk API.

example-command-with-opts.c

/*

Demonstrates how to prepare options for mongoc_client_read_command_with_opts and
mongoc_client_write_command_with_opts. First it calls "cloneCollectionAsCapped"
command with "writeConcern" option, then "distinct" command with "collation" and
"readConcern" options,

Start a MongoDB 3.4 replica set with --enableMajorityReadConcern and insert two
documents:

$ mongo
MongoDB Enterprise replset:PRIMARY> db.my_collection.insert({x: 1, y: "One"})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise replset:PRIMARY> db.my_collection.insert({x: 2, y: "Two"})
WriteResult({ "nInserted" : 1 })

Build and run the example:

gcc example-command-with-opts.c -o example-command-with-opts $(pkg-config
--cflags --libs libmongoc-1.0)
./example-command-with-opts [CONNECTION_STRING]
cloneCollectionAsCapped: { "ok" : 1 }
distinct: { "values" : [ 1, 2 ], "ok" : 1 }

*/

#include <mongoc/mongoc.h>
#include <stdio.h>
#include <stdlib.h>

int
main (int argc, char *argv[])
{
   mongoc_client_t *client;
   const char *uri_string = "mongodb://127.0.0.1/?appname=client-example";
   mongoc_uri_t *uri;
   bson_t *cmd;
   bson_t *opts;
   mongoc_write_concern_t *write_concern;
   mongoc_read_prefs_t *read_prefs;
   mongoc_read_concern_t *read_concern;
   bson_t reply;
   bson_error_t error;
   char *json;

   mongoc_init ();

   if (argc > 1) {
      uri_string = argv[1];
   }

   uri = mongoc_uri_new_with_error (uri_string, &error);
   if (!uri) {
      fprintf (stderr,
               "failed to parse URI: %s\n"
               "error message:       %s\n",
               uri_string,
               error.message);
      return EXIT_FAILURE;
   }

   client = mongoc_client_new_from_uri (uri);
   if (!client) {
      return EXIT_FAILURE;
   }

   mongoc_client_set_error_api (client, 2);

   cmd = BCON_NEW ("cloneCollectionAsCapped",
                   BCON_UTF8 ("my_collection"),
                   "toCollection",
                   BCON_UTF8 ("my_capped_collection"),
                   "size",
                   BCON_INT64 (1024 * 1024));

   /* include write concern "majority" in command options */
   write_concern = mongoc_write_concern_new ();
   mongoc_write_concern_set_wmajority (write_concern, 10000 /* wtimeoutMS */);
   opts = bson_new ();
   mongoc_write_concern_append (write_concern, opts);

   if (mongoc_client_write_command_with_opts (client, "test", cmd, opts, &reply, &error)) {
      json = bson_as_canonical_extended_json (&reply, NULL);
      printf ("cloneCollectionAsCapped: %s\n", json);
      bson_free (json);
   } else {
      fprintf (stderr, "cloneCollectionAsCapped: %s\n", error.message);
   }

   bson_free (cmd);
   bson_free (opts);

   /* distinct values of "x" in "my_collection" where "y" sorts after "one" */
   cmd = BCON_NEW ("distinct",
                   BCON_UTF8 ("my_collection"),
                   "key",
                   BCON_UTF8 ("x"),
                   "query",
                   "{",
                   "y",
                   "{",
                   "$gt",
                   BCON_UTF8 ("one"),
                   "}",
                   "}");

   read_prefs = mongoc_read_prefs_new (MONGOC_READ_SECONDARY);

   /* "One" normally sorts before "one"; make "One" sort after "one" */
   opts = BCON_NEW ("collation", "{", "locale", BCON_UTF8 ("en_US"), "caseFirst", BCON_UTF8 ("lower"), "}");

   /* add a read concern to "opts" */
   read_concern = mongoc_read_concern_new ();
   mongoc_read_concern_set_level (read_concern, MONGOC_READ_CONCERN_LEVEL_MAJORITY);

   mongoc_read_concern_append (read_concern, opts);

   if (mongoc_client_read_command_with_opts (client, "test", cmd, read_prefs, opts, &reply, &error)) {
      json = bson_as_canonical_extended_json (&reply, NULL);
      printf ("distinct: %s\n", json);
      bson_free (json);
   } else {
      fprintf (stderr, "distinct: %s\n", error.message);
   }

   bson_destroy (cmd);
   bson_destroy (opts);
   bson_destroy (&reply);
   mongoc_read_prefs_destroy (read_prefs);
   mongoc_read_concern_destroy (read_concern);
   mongoc_write_concern_destroy (write_concern);
   mongoc_uri_destroy (uri);
   mongoc_client_destroy (client);

   mongoc_cleanup ();

   return EXIT_SUCCESS;
}

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