Re: invalid memory alloc after insert with c trigger function - Mailing list pgsql-general

Dudás József <dj1999@freemail.hu> 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.

--
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com