Function bms_intersect

src/backend/nodes/bitmapset.c:255–282

* bms_intersect - set intersection */

 * bms_intersect - set intersection
 */
Bitmapset *
bms_intersect(const Bitmapset *a, const Bitmapset *b)
{
	Bitmapset  *result;
	const Bitmapset *other;
	int			resultlen;
	int			i;

	/* Handle cases where either input is NULL */
	if (a == NULL || b == NULL)
		return NULL;
	/* Identify shorter and longer input; copy the shorter one */
	if (a->nwords <= b->nwords)
	{
		result = bms_copy(a);
		other = b;
	}
	else
	{
		result = bms_copy(b);
		other = a;
	}
	/* And intersect the longer input with the result */
	resultlen = result->nwords;
	for (i = 0; i < resultlen; i++)
		result->words[i] &= other->words[i];
	return result;
}

/*
 * bms_difference - set difference (ie, A without members of B)