Provided by: libmongoc-doc_1.15.0-1_all bug


       mongoc_session_opts_set_causal_consistency - mongoc_session_opts_set_causal_consistency()


          mongoc_session_opts_set_causal_consistency (mongoc_session_opt_t *opts,
                                                      bool causal_consistency);

       Configure  causal  consistency  in a session. If true (the default), each operation in the
       session will be causally ordered after the previous read or write operation. Set to  false
       to disable causal consistency. See the MongoDB Manual Entry for Causal Consistency.

       Unacknowledged writes are not causally consistent. If you execute a write operation with a
       mongoc_write_concern_t on which you have called mongoc_write_concern_set_w with a value of
       0, the write does not participate in causal consistency.


       · opts: A mongoc_session_opt_t.

       · causal_consistency: True or false.


          mongoc_client_t *client;
          mongoc_session_opt_t *session_opts;
          mongoc_client_session_t *client_session;
          mongoc_collection_t *collection;
          bson_t insert_opts = BSON_INITIALIZER;
          bson_t *doc;
          bson_error_t error;
          bool r;

          client = mongoc_client_new ("mongodb://example/?appname=session-opts-example");
          mongoc_client_set_error_api (client, 2);

          session_opts = mongoc_session_opts_new ();
          mongoc_session_opts_set_causal_consistency (session_opts, false);
          client_session = mongoc_client_start_session (client, session_opts, &error);
          mongoc_session_opts_destroy (session_opts);

          if (!client_session) {
             fprintf (stderr, "Failed to start session: %s\n", error.message);
             abort ();

          collection = mongoc_client_get_collection (client, "test", "collection");
          doc = BCON_NEW ("_id", BCON_INT32 (1));
          r = mongoc_client_session_append (client_session, &insert_opts, NULL);
          if (!r) {
             fprintf (stderr, "mongoc_client_session_append failed: %s\n", error.message);
             abort ();

          r = mongoc_collection_insert_one (
             collection, doc, &insert_opts, NULL /* reply */, &error);

          if (!r) {
             fprintf (stderr, "Insert failed: %s\n", error.message);
             abort ();


       MongoDB, Inc


       2017-present, MongoDB, Inc

1.15.0                                     Aug 13, 2MONGOC_SESSION_OPTS_SET_CAUSAL_CONSISTENCY(3)