MONGOC_CURSOR_T(3)

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);
       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
2009-present, MongoDB, Inc.