add numeric datatype

[koshak01]

def split_by(number, length = 4):
	data = [ int(number[-length-once:len(number) - once]) for once in range(0, len(number), length)]
	data.reverse()
	return data

def numeric_formater(val):
	val = str(val)
	try:
		dots = val.index('.')
		data_base = [(2, 'h', once) for once in split_by(val[:dots], 4)]
		dots_based = "{0}{1}".format(val[dots+1:], '0'*(4 - len(val[dots+1:])%4))
		data_dots = [(2, 'h', once) for once in split_by(dots_based, 4)]
		data = data_base + data_dots
		dots_positions = len(val) - dots - 1
	except ValueError:
		data = [(2, 'h', once) for once in split_by(val, 4)]
		data_base = data
		# dots = None
		dots_positions = None

	header = [
		 (2, 'h', len(data))
		,(2, 'h', len(data_base) - 1)
		,(4, 'i', 0 if not dots_positions else dots_positions)
	]
	data = header + data
	count = sum([once[0] for once in data])
	data.insert(0, (4, 'i', count))
	format = ''.join([once[1] for once in data])
	return (format, [once[2] for once in data] )

take from https://doxygen.postgresql.org/backend_2utils_2adt_2numeric_8c.html#a57a8f8ab552bae24926d252180956958

[altaurog]

Hey, thanks for your interest, @koshak01! numeric would be a great addition to the library, but it would need a more complete implementation. I'll have a shot at it when time permits. What are your thoughts about the type of the python val? Would it serialize any type, or just decimal.Decimal?

[filippzorin]

Hey, thanks for your interest, @koshak01! numeric would be a great addition to the library, but it would need a more complete implementation. I'll have a shot at it when time permits. What are your thoughts about the type of the python val? Would it serialize any type, or just decimal.Decimal?

Hi @altaurog, I'm just started using pgcopy and faced with issue when insert int values to postgres numeric. Why you decided to serialize only decimal.Decimal? I think it would be good if at least int can be serialized to numeric. In my opinion, there is no any corner cases with int, not sure about other types which can be converted casted to decimal.Decimal, this is also discussable. What do you think about this?

[altaurog]

Hey @filippzorin, I am glad you have taken interest in this project.

I think the primary motivation was a simple and natural mapping between types. It is true that int can be serialized to numeric, but int can easily be converted first to decimal.Decimal as well. We could add some magic in the library to do that automatically for convenience, but there would have to be a compelling motivation. An int in python will normally be stored in the database as int.