class PG::BasicTypeMapForResults::WarningTypeMap

def initialize(typenames)
	@already_warned = Hash.new{|h, k| h[k] = {} }
	@typenames_by_oid = typenames
end

def typecast_result_value(result, _tuple, field)
	format = result.fformat(field)
	oid = result.ftype(field)
	unless @already_warned[format][oid]
		STDERR.puts "Warning: no type cast defined for type #{@typenames_by_oid[format][oid].inspect} with oid #{oid}. Please cast this type explicitly to TEXT to be safe for future changes."
		 @already_warned[format][oid] = true
	end
	super
end