Re: Issue on C function that reads int2[] (using "int2vector")
| От | Rodrigo Hjort |
|---|---|
| Тема | Re: Issue on C function that reads int2[] (using "int2vector") |
| Дата | |
| Msg-id | CAAjEfRyLvNANio5O45+tVtT+szdfakxYbFJqT_EC8dycWqm+dQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Issue on C function that reads int2[] (using "int2vector") (Tom Lane <tgl@sss.pgh.pa.us>) |
| Список | pgsql-hackers |
2015-11-30 0:39 GMT-02:00 Tom Lane:
Rodrigo Hjort writes:
> I created a custom C function with this signature:
> CREATE FUNCTION calculate_hash(numbers int2[])
> RETURNS int8
> AS 'MODULE_PATHNAME', 'pg_calculate_hash'
> LANGUAGE C
> IMMUTABLE STRICT;
> And here is the function source code (inspired in codes I found in
> src/backend/utils/adt/int.c):
> PG_FUNCTION_INFO_V1(pg_calculate_hash);
> Datum
> pg_calculate_hash(PG_FUNCTION_ARGS)
> {
> int2vector *int2Array = (int2vector *) PG_GETARG_POINTER(0);
Nope. int2vector is not the same as int2[]. It might occasionally seem
to work, but in general it's not the same type. And this particular
coding won't work at all on on-disk int2[] data, because it doesn't
account for toasting.
regards, tom lane
Thanks for the advice, Tom.
I ended up with the following code, which worked successfully:
#define ARRPTR16(x) ((uint16 *) ARR_DATA_PTR(x))
#define ARRNELEMS(x) ArrayGetNItems(ARR_NDIM(x), ARR_DIMS(x))
#define ARRISEMPTY(x) (ARRNELEMS(x) == 0)
PG_FUNCTION_INFO_V1(pg_calculate_hash);
Datum
pg_calculate_hash(PG_FUNCTION_ARGS)
{
ArrayType *a = PG_GETARG_ARRAYTYPE_P_COPY(0);
unsigned int i, qtd, tipo, nums[MAX_NUMEROS];
uint16 *da;
qtd = ARRNELEMS(a);
tipo = ARR_ELEMTYPE(a);
da = ARRPTR16(a);
elog(DEBUG1, "pg_calculate_hash(qtd=%d, tipo=%d)", qtd, tipo);
[...]
pfree(a);
PG_RETURN_INT64(hash);
}
Regards,
Rodrigo Hjort
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