Function array_fill

src/backend/utils/adt/arrayfuncs.c:5914–5947

* array_fill * Create and fill array with default lower bounds. */

 *		Create and fill array with default lower bounds.
 */
Datum
array_fill(PG_FUNCTION_ARGS)
{
	ArrayType  *dims;
	ArrayType  *result;
	Oid			elmtype;
	Datum		value;
	bool		isnull;

	if (PG_ARGISNULL(1))
		ereport(ERROR,
				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
				 errmsg("dimension array or low bound array cannot be null")));

	dims = PG_GETARG_ARRAYTYPE_P(1);

	if (!PG_ARGISNULL(0))
	{
		value = PG_GETARG_DATUM(0);
		isnull = false;
	}
	else
	{
		value = 0;
		isnull = true;
	}

	elmtype = get_fn_expr_argtype(fcinfo->flinfo, 0);
	if (!OidIsValid(elmtype))
		elog(ERROR, "could not determine data type of input");

	result = array_fill_internal(dims, NULL, value, isnull, elmtype, fcinfo);
	PG_RETURN_ARRAYTYPE_P(result);
}

static ArrayType *
create_array_envelope(int ndims, int *dimv, int *lbsv, int nbytes,