Guy Deleeuw <G(dot)De_Leeuw(at)eurofer(dot)be> writes:
> I cannot convert properly a cstring to a Datum :
Well, CStringGetDatum would be the proper thing to use if you meant to
produce a Datum of type "cstring". But what you need here is a Datum
of the same type as the target column, which evidently isn't cstring.
Most likely you need to convert the string to type text.
regards, tom lane