void

       MongoDB, Inc

       2009-present, MongoDB, Inc.

1.30.4                                            Jun 08, 2025     MONGOC_SESSION_OPTS_SET_CAUSAL_CONSISTENCY(3)

          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 ();
          }

       • opts: A mongoc_session_opt_t.

       • causal_consistency: True or false.

          void
          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 theMongoDBManualEntryforCausalConsistency.

       Causal  consistency and snapshot reads are mutually exclusive. Attempting to set both to true will result
       in an error. See mongoc_session_opts_set_snapshot().

       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.