mongoc_cursor_t *
mongoc_collection_find_with_opts (mongoc_collection_t *collection,
                                  const bson_t *filter,
                                  const bson_t *opts,
                                  const mongoc_read_prefs_t *read_prefs)



Query on collection, passing arbitrary query options to the server in opts.

To target a specific server, include an integer "serverId" field in opts with an id obtained first by calling mongoc_client_select_server(), then mongoc_server_description_id() on its return value.


A newly allocated mongoc_cursor_t that must be freed with mongoc_cursor_destroy().


Print First Ten Documents in a Collection
#include <mongoc.h>
#include <stdio.h>

static void
print_ten_documents (mongoc_collection_t *collection)
   bson_t *filter;
   bson_t *opts;
   mongoc_cursor_t *cursor;
   bson_error_t error;
   const bson_t *doc;
   char *str;

   /* filter by "foo": 1, order by "bar" descending */
   filter = BCON_NEW ("foo", BCON_INT32 (1));
   opts = BCON_NEW (
      "limit", BCON_INT64 (10), "sort", "{", "bar", BCON_INT32 (-1), "}");

   cursor = mongoc_collection_find_with_opts (collection, filter, opts, NULL);

   while (mongoc_cursor_next (cursor, &doc)) {
      str = bson_as_json (doc, NULL);
      printf ("%s\n", str);
      bson_free (str);

   if (mongoc_cursor_error (cursor, &error)) {
      fprintf (stderr, "An error occurred: %s\n", error.message);

   mongoc_cursor_destroy (cursor);
   bson_destroy (filter);
   bson_destroy (opts);
More examples of modifying the query with opts:
bson_t *filter;
bson_t *opts;
mongoc_read_prefs_t *read_prefs;

filter = BCON_NEW ("foo", BCON_INT32 (1));

/* Include "field_name_one" and "field_name_two" in "projection", omit
 * others. "_id" must be specifically removed or it is included by default.
opts = BCON_NEW ("projection", "{",
                    "field_name_one", BCON_BOOL (true),
                    "field_name_two", BCON_BOOL (true),
                    "_id", BCON_BOOL (false),
                 "tailable", BCON_BOOL (true),
                 "awaitData", BCON_BOOL (true),
                 "sort", "{", "bar", BCON_INT32 (-1), "}",
                 "collation", "{",
                    "locale", BCON_UTF8("en_US"),
                    "caseFirst", BCON_UTF8 ("lower"),

read_prefs = mongoc_read_prefs_new (MONGOC_READ_SECONDARY);

cursor =
   mongoc_collection_find_with_opts (collection, filter, opts, read_prefs);

The following options are supported.

Option BSON type Option BSON type
projection document maxScan non-negative int64
sort document maxTimeMS non-negative int64
skip non-negative int64 maxAwaitTimeMS non-negative int64
limit non-negative int64 min document
batchSize non-negative int64 noCursorTimeout bool
exhaust bool oplogReplay bool
hint string or document returnKey bool
allowPartialResults bool showRecordId bool
awaitData bool singleBatch bool
collation document snapshot bool
comment string tailable bool
max document    

All options are documented in the reference page for the "find" command in the MongoDB server manual, except for "maxAwaitTimeMS".

"maxAwaitTimeMS" is the maximum amount of time for the server to wait on new documents to satisfy a query, if "tailable" and "awaitData" are both true. If no new documents are found, the tailable cursor receives an empty batch. The "maxAwaitTimeMS" option is ignored for MongoDB older than 3.4.

For some options like "collation", the driver returns an error if the server version is too old to support the feature. Any fields in opts that are not listed here are passed to the server unmodified.

See Also

The "find" command in the MongoDB Manual. All options listed there are supported by the C Driver. For MongoDB servers before 3.2, or for exhaust queries, the driver transparently converts the query to a legacy OP_QUERY message.

The "explain" command

With MongoDB before 3.2, a query with option $explain: true returns information about the query plan, instead of the query results. Beginning in MongoDB 3.2, there is a separate "explain" command. The driver will not convert "$explain" queries to "explain" commands, you must call the "explain" command explicitly:

/* MongoDB 3.2+, "explain" command syntax */
command = BCON_NEW ("explain", "{",
                    "find", BCON_UTF8 ("collection_name"),
                    "filter", "{", "foo", BCON_INT32 (1), "}",

mongoc_collection_command_simple (collection, command, NULL, &reply, &error);

See Also

The "explain" command in the MongoDB Manual.