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 maybe-NULL pointer to overwritable storage for a bson_t to contain the results.

       • 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.

       • comment: A bson_value_t 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.

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