mongoc_collection_read_command_with_opts

bool
mongoc_collection_read_command_with_opts (mongoc_collection_t *collection,
                                          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_collection_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.

See the example for transactions <#mongoc-client-session-start-transaction-example> and for the "distinct" command with opts <#mongoc-client-read-command-with-opts-example>.

reply is always initialized, and must be freed with bson_destroy() <https://www.mongoc.org/libbson/current/bson_destroy.html>.

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_collection_command_with_opts() <>) instead.

• collection: A mongoc_collection_t <>.
• command: A bson_t <https://www.mongoc.org/libbson/current/bson_t.html> containing the command specification.
• read_prefs: An optional mongoc_read_prefs_t <>.
• opts: A bson_t <https://www.mongoc.org/libbson/current/bson_t.html> containing additional options.
• reply: A maybe-NULL pointer to overwritable storage <https://www.mongodb.com/docs/languages/c/c-driver/current/libbson/guides/lifetimes/#overwritable-storage> for a bson_t <https://www.mongoc.org/libbson/current/bson_t.html> 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 collection, 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 <https://www.mongodb.com/docs/languages/c/c-driver/current/libmongoc/guides/bulk/#setting-collation-order>, and the MongoDB Manual entry on Collation <https://www.mongodb.com/docs/manual/reference/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 <https://www.mongodb.com/docs/manual/reference/command/> 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.

See the example code for mongoc_client_read_command_with_opts() <>.

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