> I have a java application which generates inperformant query > plans.
> Index Cond: ((lat >= $3) AND (lat <= $4) AND (lon >= $1) AND (lon > <= $2))
> Filter: (((lon)::double precision >= $1) AND ((lon)::double > precision <= $2) AND ((lat)::double precision >= $3) AND > ((lat)::double precision <= $4))
It is the cast of the table columns to double precision which is taking the index out of play.
What are the data types of those columns? What does the code look like where you're setting the values for the parameters? If nothing else, writing the query so that the parameters are cast to the right type before use might solve the problem, but I would start by looking at the object classes used in the Java app.
