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 false 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

       2018, MongoDB, Inc