class PG::BasicTypeMapForQueries

res = conn.exec_params( “SELECT $1”, [5] )
# The format of the parameter is set to 1 (binary) and the OID of this parameter is set to 20 (int8).
# Execute a query. The Integer param value is typecasted internally by PG::BinaryEncoder::Int8.
conn.type_map_for_queries = PG::BasicTypeMapForQueries.new(conn)
# Assign a default ruleset for type casts of input and output values.
conn = PG::Connection.new
Example:
encoders and decoders for the values to be sent.
own derivation of PG::TypeMapByClass or another set of rules to choose suitable
Higher level libraries will most likely not make use of this class, but use their
Query params are type casted based on the class of the given value.
PostgreSQL’s pg_type table in PG::BasicTypeMapForQueries.new .
OIDs of supported type casts are not hard-coded in the sources, but are retrieved from the
Simple set of rules for type casting common Ruby types to PostgreSQL.

def array_encoders_by_klass 

def array_encoders_by_klass
	DEFAULT_ARRAY_TYPE_MAP.inject({}) do |h, (klass, (format, name))|
		h[klass] = coder_by_name(format, :encoder, name)
		h
	end
end

def coder_by_name(format, direction, name) 

def coder_by_name(format, direction, name)
	check_format_and_direction(format, direction)
	@coder_maps[format][direction].coder_by_name(name)
end

def get_array_type(value) 

def get_array_type(value)
	elem = value
	while elem.kind_of?(Array)
		elem = elem.first
	end
	@array_encoders_by_klass[elem.class] ||
			elem.class.ancestors.lazy.map{|ancestor| @array_encoders_by_klass[ancestor] }.find{|a| a } ||
			@anyarray_encoder
end

def initialize(connection) 

def initialize(connection)
	@coder_maps = build_coder_maps(connection)
	populate_encoder_list
	@array_encoders_by_klass = array_encoders_by_klass
	@anyarray_encoder = coder_by_name(0, :encoder, '_any')
end

def populate_encoder_list 

def populate_encoder_list
	DEFAULT_TYPE_MAP.each do |klass, selector|
		if Array === selector
			format, name, oid_name = selector
			coder = coder_by_name(format, :encoder, name).dup
			if oid_name
				coder.oid = coder_by_name(format, :encoder, oid_name).oid
			else
				coder.oid = 0
			end
			self[klass] = coder
		else
			self[klass] = selector
		end
	end
end