readable.rb in mongo-2.7.1

- old
+ new

@@ -120,10 +120,11 @@
         # @option opts :limit [ Integer ] Max number of docs to count.
         # @option opts :max_time_ms [ Integer ] The maximum amount of time to allow the
         #   command to run.
         # @option opts [ Hash ] :read The read preference options.
         # @option opts [ Hash ] :collation The collation to use.
+        # @option opts [ Mongo::Session ] :session The session to use for the operation.
         #
         # @return [ Integer ] The document count.
         #
         # @since 2.0.0
         #
@@ -180,11 +181,13 @@
           pipeline = [:'$match' => filter]
           pipeline << { :'$skip' => opts[:skip] } if opts[:skip]
           pipeline << { :'$limit' => opts[:limit] } if opts[:limit]
           pipeline << { :'$group' => { _id: nil, n: { :'$sum' => 1 } } }
 
-          opts.select! { |k, _| [:hint, :max_time_ms, :read, :collation].include?(k) }
-          aggregate(pipeline, opts).first['n'].to_i
+          opts.select! { |k, _| [:hint, :max_time_ms, :read, :collation, :session].include?(k) }
+          first = aggregate(pipeline, opts).first
+          return 0 unless first
+          first['n'].to_i
         end
 
         # Gets an estimate of the count of documents in a collection using collection metadata.
         #
         # @example Get the number of documents in the collection.