mongoc_collection_count_documents - Man Page

mongoc_collection_count_documents()

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:

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);
   }
}

Migrating from Deprecated Count Functions

When migrating to mongoc_collection_count_documents from the deprecated mongoc_collection_count or mongoc_collection_count_with_opts, the following query operators in the filter must be replaced:

OperatorReplacement
$where$expr
$near$geoWithin with $center
$nearSphere$geoWithin with $centerSphere

$expr requires MongoDB 3.6+

See Also

mongoc_collection_estimated_document_count()

Author

MongoDB, Inc

Info

Apr 09, 2021 1.17.5 libmongoc