MONGOC_COLLECTION_COUNT_DOCUMENTS(3)

NAME
mongoc_collection_count_documents - 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

    •   collection: A mongoc_collection_t.

    •   filter: A bson_t containing the filter.

    •   opts: A bson_t, NULL to ignore.

    •   read_prefs: A mongoc_read_prefs_t or NULL.

    •   reply: A location for an uninitialized bson_t to store the command reply, NULL to ignore. If not NULL, reply will be initialized.

    •   error: An optional location for a bson_error_t or NULL.

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, and the MongoDB Manual entry on 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.

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:
Operator | Replacement
$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

COPYRIGHT
2017-present, MongoDB, Inc