Thank you and other helpfully peoples the interest about my first steps
in your world. I learned more than I hope.
This function work fine now.
Can you to offer me place where I find these information, because I read
the postgresql source code to find these macros.
Regards,
Josef
Dudás József <dj1999@xxxxxxxxxxx> writes:
Yes! You are right! Now must me find out how to convert char* to numeric datum
and double to numeric datum and numeric datum to double :)
If you have a char* you can usually call a types input function which is
usally "type_in" or "typein" like:
DirectFunctionCall1(type_in, str).
However in the case of numeric you need to pass a couple extra parameters:
DirectFunctionCall3(numeric_in, str, 0, -1 + VARHDRSZ)
To convert to a float8 datum you would use
DirectFunctionCall1(numeric_float,num).
To convert from a Postgres float8 datum to an actual double you can just call
the macros DatumGetFloat8 and Float8GetDatum. This makes your code depend on
the internal representation of float8 as a C double but it's better than the
alternative.
