Re: How to convert a double value to a numeric datum type in pgsql?

hello

you have to look to postgresql/src/backend/utils/adt/numeric.c functions -

then you can call float8_numeric

Numeric result = DatumGetNumeric(DirectFunctionCall1(float8_numeric,
Float8GetDatum(dx));

regards

Pavel

2014-02-24 7:45 GMT+01:00 Felix.徐 <ygnhzeus(at)gmail(dot)com>:

> Hi all,
> 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..
>
>
>
>
>