NAME

       mongoc_cursor_error_document - mongoc_cursor_error_document()

SYNOPSIS

          bool
          mongoc_cursor_error_document (mongoc_cursor_t *cursor,
                                        bson_error_t *error,
                                        const bson_t **reply);

PARAMETERS

       • cursor: A mongoc_cursor_t.

       • error: An optional location for a bson_error_t or NULL.

       • reply: A location for a bson_t.

DESCRIPTION

       This function checks to see if an error has occurred while iterating the cursor.

       If  an error occurred client-side, for example if there was a network error or timeout, or
       the cursor was created with invalid parameters,  then  reply  is  set  to  an  empty  BSON
       document.  If  an  error occurred server-side, reply is set to the server's reply document
       with information about the error.

ERRORS

       Errors are propagated via the error and reply parameters.

RETURNS

       False if no error has occurred, otherwise true and error is set.

       If the function returns true and reply is not NULL, then reply is set to a  pointer  to  a
       BSON  document,  which  is  either  empty  or the server's error response. The document is
       invalid after the cursor is freed with mongoc_cursor_destroy().

EXAMPLE

       This example shows the difference between a client-side  and  server-side  error.  If  the
       client  cannot connect to the server, for example, the error message includes "No suitable
       servers found" and reply is set to an empty BSON document.

       On the other hand, if the client connects to  the  server  successfully  and  attempts  to
       execute  an invalid query, the error message comes from the server and reply is set to the
       server's reply document, with fields errmsg and code.

          void
          run_query (const char *uri_str, const bson_t *query)
          {
             mongoc_client_t *client;
             mongoc_collection_t *collection;
             mongoc_cursor_t *cursor;
             const bson_t *doc;
             bson_error_t error;
             const bson_t *reply;
             char *str;

             client = mongoc_client_new (uri_str);

             mongoc_client_set_error_api (client, 2);

             collection = mongoc_client_get_collection (client, "db", "collection");
             cursor = mongoc_collection_find_with_opts (
                collection,
                query,
                NULL,  /* additional options */
                NULL); /* read prefs, NULL for default */

             /* this loop is never run: mongoc_cursor_next immediately returns false */
             while (mongoc_cursor_next (cursor, &doc)) {
             }

             if (mongoc_cursor_error_document (cursor, &error, &reply)) {
                str = bson_as_json (reply, NULL);
                fprintf (stderr, "Cursor Failure: %s\nReply: %s\n", error.message, str);
                bson_free (str);
             }

             mongoc_cursor_destroy (cursor);
             mongoc_collection_destroy (collection);
             mongoc_client_destroy (client);
          }

          int
          main (int argc, char *argv[])
          {
             bson_t *good_query;
             bson_t *bad_query;

             mongoc_init ();

             /* find documents matching the query {"x": 1} */
             good_query = BCON_NEW ("x", BCON_INT64 (1));

             /* Cause a network error. This will print an error and empty reply document:
              *
              * Cursor Failure: No suitable servers found (`serverSelectionTryOnce` set):
              *     [Failed to resolve 'fake-domain']
              *
              * Reply: { }
              *
              */
             run_query ("mongodb://fake-domain/?appname=cursor-example", good_query);

             /* invalid: {"x": {"$badOperator": 1}} */
             bad_query = BCON_NEW ("x", "{", "$badOperator", BCON_INT64 (1), "}");

             /* Cause a server error. This will print an error and server reply document:
              *
              * Cursor Failure: unknown operator: $badOperator
              *
              * Reply:
              * {"ok": 0.0,
              *  "errmsg":"unknown operator: $badOperator",
              *  "code": 2,
              *  "codeName":"BadValue"
              * }
              *
              */
             run_query ("mongodb://localhost/?appname=cursor-example", bad_query);

             bson_destroy (good_query);
             bson_destroy (bad_query);

             mongoc_cleanup ();

             return 0;
          }

AUTHOR

       MongoDB, Inc

COPYRIGHT

       2017-present, MongoDB, Inc