How do socialist countries prevent unemployment while still increasing innovation?

Technical innovation increases the productivity of labor in industry. If production shouldn't be wasteful, there needs to be a reduction in workers. Where do all these workers go if there's no unemployment? In a capitalist economy the workers are left to die on the streets but in a socialist economy they need to get a job again, right? Does the state take the burden of cost of reeducating these workers to enter another field and factor this into calculations when introducing new technology?