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MONGOC_COLLECTION_COUNT_DOCUMENTS(3) libmongoc MONGOC_COLLECTION_COUNT_DOCUMENTS(3)

SYNOPSIS

int64_t
mongoc_collection_count_documents (mongoc_collection_t *collection,


                                   const bson_t *filter,


                                   const bson_t *opts,


                                   const mongoc_read_prefs_t *read_prefs,


                                   bson_t *reply,


                                   bson_error_t *error);


PARAMETERS


opts may be NULL or a BSON document with additional command options:

  • readConcern: Construct a mongoc_read_concern_t <> and use mongoc_read_concern_append() <> to add the read concern to opts. See the example code for mongoc_client_read_command_with_opts() <>. Read concern requires MongoDB 3.2 or later, otherwise an error is returned.
  • sessionId: First, construct a mongoc_client_session_t <> with mongoc_client_start_session() <>. You can begin a transaction with mongoc_client_session_start_transaction() <>, optionally with a mongoc_transaction_opt_t <> that overrides the options inherited from collection, and use mongoc_client_session_append() <> to add the session to opts. See the example code for mongoc_client_session_t <>.
  • collation: Configure textual comparisons. See Setting Collation Order <https://www.mongodb.com/docs/languages/c/c-driver/current/libmongoc/guides/bulk/#setting-collation-order>, and the MongoDB Manual entry on Collation <https://www.mongodb.com/docs/manual/reference/collation/>. Collation requires MongoDB 3.2 or later, otherwise an error is returned.
  • serverId: To target a specific server, include an int32 "serverId" field. Obtain the id by calling mongoc_client_select_server() <>, then mongoc_server_description_id() <> on its return value.
  • skip: An int specifying how many documents matching the query should be skipped before counting.
  • limit: An int specifying the maximum number of documents to count.
  • comment: A bson_value_t <https://www.mongoc.org/libbson/current/bson_value_t.html> specifying the comment to attach to this command. The comment will appear in log messages, profiler output, and currentOp output. Only string values are supported prior to MongoDB 4.4.
  • hint: A document or string that specifies the index to use to support the query predicate.

Other options are included in the sent aggregate command. For a list of all options, see the MongoDB Manual entry on the aggregate command <https://www.mongodb.com/docs/manual/reference/command/aggregate/>.

DESCRIPTION

This functions executes a count query on collection. In contrast with mongoc_collection_estimated_document_count() <>, the count returned is guaranteed to be accurate.

This function is considered a retryable read operation. Upon a transient error (a network error, errors due to replica set failover, etc.) the operation is safely retried once. If retryreads is false in the URI (see mongoc_uri_t <>) the retry behavior does not apply.

ERRORS

Errors are propagated via the error parameter.

RETURNS

-1 on failure, otherwise the number of documents counted.

EXAMPLE

#include <bson/bson.h>
#include <mongoc/mongoc.h>
#include <stdio.h>
static void
print_count (mongoc_collection_t *collection, bson_t *filter)
{


   bson_error_t error;


   int64_t count;


   bson_t* opts = BCON_NEW ("skip", BCON_INT64(5));


   count = mongoc_collection_count_documents (


      collection, filter, opts, NULL, NULL, &error);


   bson_destroy (opts);


   if (count < 0) {


      fprintf (stderr, "Count failed: %s\n", error.message);


   } else {


      printf ("%" PRId64 " documents counted.\n", count);


   }
}


See also:

mongoc_collection_estimated_document_count() <>



Author

MongoDB, Inc

Copyright

2009-present, MongoDB, Inc.

December 11, 2025 2.2.1