Function mda_get_offset_values

src/backend/utils/adt/arrayutils.c:174–187

* From products of whole-array dimensions and spans of a sub-array, * compute offset distances needed to step through subarray within array * * We assume caller has validated dimensions, so overflow is impossible */

 * We assume caller has validated dimensions, so overflow is impossible
 */
void
mda_get_offset_values(int n, int *dist, const int *prod, const int *span)
{
	int			i,
				j;

	dist[n - 1] = 0;
	for (j = n - 2; j >= 0; j--)
	{
		dist[j] = prod[j] - 1;
		for (i = j + 1; i < n; i++)
			dist[j] -= (span[i] - 1) * prod[i];
	}
}

/*
 * Generates the tuple that is lexicographically one greater than the current