I'm talking about the source code of pgsql and I want to know how the typing system works in pgsql.
A few functions can help us do the type conversion, for example:
Int32GetDatum -- convert a integer to a datum
Float8GetDatum -- convert double to a datum
cstring_to_text -- convert a string to a text
...
but there are a lot of types in pgsql,how to choose the corresponding function? or is there a more automatic way to do the type conversion(raw chars to a datum, suppose I have the corresponding Form_pg_type instance)?
I ask this question because I don't know how to convert a double value to a numeric datum(the field's type is numeric(10,2)), pg_type shows that numeric's typlen is -1 whose length is variable thus Float8GetDatum is not working..
