"Merlin Moncure" <mmoncure(at)gmail(dot)com> writes:
> well, there aren't all that many examples in contrib, and some of the
> ones that are there look like this (edited) from tsearch2:
> Datum
> rewrite_accum(PG_FUNCTION_ARGS)
> {
> QUERYTYPE *acc = (QUERYTYPE *) PG_GETARG_POINTER(0);
> ArrayType *qa = (ArrayType *)
> DatumGetPointer(PG_DETOAST_DATUM_COPY(PG_GETARG_DATUM(1)));
> if (acc == NULL || PG_ARGISNULL(0))
> {
That might be safe but it sure looks like bad practice to me.
In particular I think it's unwise to assume that the Datum value
for a null will always be zero.
regards, tom lane