$query does not work on mongodb input

I typed to Query expression(JSON) field at Query tab on MongoDB Input as follows.
{ "$query" : {} }
But No records are retrieved.

All collection records are retrieved when typing following words to Query expression(JSON) field.
{}

I want to set $query and $orderby to Query expression(JSON) field.
Please show me how to solve this problem ?

Environment
-Pentaho data integrateiton 5.0.1 (pdi-ce-5.0.1-stable.zip)
installed at Windows XP SP2 32bit
-MongoDB 2.4.4
installed at CentOS 6.4 64bit