Function compute_tuples_needed

src/backend/executor/nodeLimit.c:455–462

* Compute the maximum number of tuples needed to satisfy this Limit node. * Return a negative value if there is not a determinable limit. */

 * Return a negative value if there is not a determinable limit.
 */
static int64
compute_tuples_needed(LimitState *node)
{
	if ((node->noCount) || (node->limitOption == LIMIT_OPTION_WITH_TIES))
		return -1;
	/* Note: if this overflows, we'll return a negative value, which is OK */
	return node->count + node->offset;
}

/* ----------------------------------------------------------------
 *		ExecInitLimit