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.

• 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 database, collection, or 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.