--- name: "mongoc_client_read_command_with_opts" section: "3" platform: "linux" package: "libmongoc-doc" version: "1.30.4-1+deb13u3" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/mongoc_client_read_command_with_opts" --- # mongoc\_client\_read\_command\_with\_opts(3) ## SYNOPSIS ``` bool mongoc_client_read_command_with_opts (mongoc_client_t *client, const char *db_name, const bson_t *command, const mongoc_read_prefs_t *read_prefs, 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 read, 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 read such as "count" or "distinct". Read preferences, read concern, and collation can be overridden by various sources. In a transaction, read concern and write concern are prohibited in **opts** and the read preference must be primary or NULL. The highest-priority sources for these options are listed first in the following table. No write concern is applied. | | | | | --- | --- | --- | | Read Preferences | Read Concern | Collation | | **read\_prefs** | **opts** | **opts** | | Transaction | Transaction | | | **client** | | | *See the example for transactions* and for *the "distinct" command with opts*. **reply** is always initialized, and must be freed with *bson\_destroy()*. This function is considered a retryable read operation. Upon a transient error (a network error, errors due to replica set failover, etc.) the operation is safely retried once. If **retryreads** is false in the URI (see *mongoc\_uri\_t*) the retry behavior does not apply. Retry logic occurs regardless of the underlying command. Retrying **mapReduce** has the potential for degraded performance. Retrying a **getMore** command has the potential to miss results. For those commands, use generic command helpers (like *mongoc\_client\_command\_with\_opts()*) instead. ## PARAMETERS - • **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. - • **read\_prefs**: An optional *mongoc\_read\_prefs\_t*. - • **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: - • **readConcern**: Construct a *mongoc\_read\_concern\_t* and use *mongoc\_read\_concern\_append()* to add the read concern to **opts**. See the example code for *mongoc\_client\_read\_command\_with\_opts()*. Read concern requires MongoDB 3.2 or later, otherwise an error is returned. - • **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 Errors are propagated via the **error** parameter. ## RETURNS Returns **true** if successful. Returns **false** and sets **error** if there are invalid arguments or a server or network error. ## EXAMPLE 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 $(pkg-config --cflags --libs libmongoc-1.0) ./example-command-with-opts [CONNECTION_STRING] cloneCollectionAsCapped: { "ok" : 1 } distinct: { "values" : [ 1, 2 ], "ok" : 1 } */ #include #include #include int main (int argc, char *argv[]) { mongoc_client_t *client; const char *uri_string = "mongodb://127.0.0.1/?appname=client-example"; mongoc_uri_t *uri; bson_t *cmd; bson_t *opts; mongoc_write_concern_t *write_concern; mongoc_read_prefs_t *read_prefs; mongoc_read_concern_t *read_concern; bson_t reply; bson_error_t error; char *json; mongoc_init (); if (argc > 1) { uri_string = argv[1]; } uri = mongoc_uri_new_with_error (uri_string, &error); if (!uri) { fprintf (stderr, "failed to parse URI: %s\n" "error message: %s\n", uri_string, error.message); return EXIT_FAILURE; } client = mongoc_client_new_from_uri (uri); if (!client) { return EXIT_FAILURE; } mongoc_client_set_error_api (client, 2); cmd = BCON_NEW ("cloneCollectionAsCapped", BCON_UTF8 ("my_collection"), "toCollection", BCON_UTF8 ("my_capped_collection"), "size", BCON_INT64 (1024 * 1024)); /* include write concern "majority" in command options */ write_concern = mongoc_write_concern_new (); mongoc_write_concern_set_wmajority (write_concern, 10000 /* wtimeoutMS */); opts = bson_new (); mongoc_write_concern_append (write_concern, opts); if (mongoc_client_write_command_with_opts (client, "test", cmd, opts, &reply, &error)) { json = bson_as_canonical_extended_json (&reply, NULL); printf ("cloneCollectionAsCapped: %s\n", json); bson_free (json); } else { fprintf (stderr, "cloneCollectionAsCapped: %s\n", error.message); } bson_free (cmd); bson_free (opts); /* distinct values of "x" in "my_collection" where "y" sorts after "one" */ cmd = BCON_NEW ("distinct", BCON_UTF8 ("my_collection"), "key", BCON_UTF8 ("x"), "query", "{", "y", "{", "$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; } ``` ## AUTHOR MongoDB, Inc ## COPYRIGHT 2009-present, MongoDB, Inc.