Function array_to_jsonb_internal

src/backend/utils/adt/jsonb.c:985–1028

* Turn an array into JSON. */

 * Turn an array into JSON.
 */
static void
array_to_jsonb_internal(Datum array, JsonbInState *result)
{
	ArrayType  *v = DatumGetArrayTypeP(array);
	Oid			element_type = ARR_ELEMTYPE(v);
	int		   *dim;
	int			ndim;
	int			nitems;
	int			count = 0;
	Datum	   *elements;
	bool	   *nulls;
	int16		typlen;
	bool		typbyval;
	char		typalign;
	JsonbTypeCategory tcategory;
	Oid			outfuncoid;

	ndim = ARR_NDIM(v);
	dim = ARR_DIMS(v);
	nitems = ArrayGetNItems(ndim, dim);

	if (nitems <= 0)
	{
		result->res = pushJsonbValue(&result->parseState, WJB_BEGIN_ARRAY, NULL);
		result->res = pushJsonbValue(&result->parseState, WJB_END_ARRAY, NULL);
		return;
	}

	get_typlenbyvalalign(element_type,
						 &typlen, &typbyval, &typalign);

	jsonb_categorize_type(element_type,
						  &tcategory, &outfuncoid);

	deconstruct_array(v, element_type, typlen, typbyval,
					  typalign, &elements, &nulls,
					  &nitems);

	array_dim_to_jsonb(result, 0, ndim, dim, elements, nulls, &count, tcategory,
					   outfuncoid);

	pfree(elements);
	pfree(nulls);
}

/*
 * Turn a composite / record into JSON.