NAME

       mongoc_collection_estimated_document_count - mongoc_collection_estimated_document_count()

SYNOPSIS

          int64_t
          mongoc_collection_estimated_document_count (mongoc_collection_t *collection,
                                                      const bson_t *opts,
                                                      const mongoc_read_prefs_t *read_prefs,
                                                      bson_t *reply,
                                                      bson_error_t *error);

PARAMETERS

       • collection: A mongoc_collection_t.

       • 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_count_documents(), the count returned is not 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 *query)
          {
             bson_error_t error;
             int64_t count;
             bson_t* opts = BCON_NEW ("skip", BCON_INT64(5));

             count = mongoc_collection_estimated_document_count (
                collection, 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_count_documents()

AUTHOR

       MongoDB, Inc

COPYRIGHT

       2017-present, MongoDB, Inc

1.21.0                                     Feb 09, 2MONGOC_COLLECTION_ESTIMATED_DOCUMENT_COUNT(3)