MONGOC_CURSOR_T(3)

NAME
mongoc_cursor_t - mongoc_cursor_t

Client-side cursor abstraction

SYNOPSIS

        typedef struct _mongoc_cursor_t mongoc_cursor_t;

mongoc_cursor_t provides access to a MongoDB query cursor. It wraps up the wire protocol negotiation required to initiate a query and retrieve an unknown number of documents.

Common cursor operations include:

    •   Determine which host we've connected to with mongoc_cursor_get_host().

    •   Retrieve more records with repeated calls to mongoc_cursor_next().

    •   Clone a query to repeat execution at a later point with mongoc_cursor_clone().

    •   Test for errors with mongoc_cursor_error().

Cursors are lazy, meaning that no connection is established and no network traffic occurs until the first call to mongoc_cursor_next().

THREAD SAFETY

mongoc_cursor_t is NOT thread safe. It may only be used from within the thread in which it was created.

EXAMPLE

Query MongoDB and iterate results

        /* gcc example-client.c -o example-client $(pkg-config --cflags --libs
         * libmongoc-1.0) */

        /* ./example-client [CONNECTION_STRING [COLLECTION_NAME]] */

        #include <mongoc/mongoc.h>
        #include <stdio.h>
        #include <stdlib.h>

        int
        main (int argc, char *argv[])
        {
           mongoc_client_t *client;
           mongoc_collection_t *collection;
           mongoc_cursor_t *cursor;
           bson_error_t error;
           const bson_t *doc;
           const char *collection_name = "test";
           bson_t query;
           char *str;
           const char *uri_string = "mongodb://127.0.0.1/?appname=client-example";
           mongoc_uri_t *uri;

           mongoc_init ();
           if (argc > 1) {
              uri_string = argv[1];
           }

           if (argc > 2) {
              collection_name = argv[2];
           }

           uri = mongoc_uri_new_with_error (uri_string, &error);
           if (!uri) {
              fprintf (stderr,
                       "failed to parse URI: %s\n"
                       "error message:       %s\n",
                       uri_string,
                       error.message);
              return EXIT_FAILURE;
           }

           client = mongoc_client_new_from_uri (uri);
           if (!client) {
              return EXIT_FAILURE;
           }

           mongoc_client_set_error_api (client, 2);

           bson_init (&query);

        #if 0
           bson_append_utf8 (&query, "hello", -1, "world", -1);
        #endif

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

           while (mongoc_cursor_next (cursor, &doc)) {
              str = bson_as_canonical_extended_json (doc, NULL);
              fprintf (stdout, "%s\n", str);
              bson_free (str);
           }

           if (mongoc_cursor_error (cursor, &error)) {
              fprintf (stderr, "Cursor Failure: %s\n", error.message);
              return EXIT_FAILURE;
           }

           bson_destroy (&query);
           mongoc_cursor_destroy (cursor);
           mongoc_collection_destroy (collection);
           mongoc_uri_destroy (uri);
           mongoc_client_destroy (client);
           mongoc_cleanup ();

           return EXIT_SUCCESS;
        }

AUTHOR
MongoDB, Inc

COPYRIGHT
2017-present, MongoDB, Inc