Comment 7 for bug 1825152

also relevant, from http://docs.openvswitch.org/en/latest/faq/issues/

 I want to add thousands of ports to an Open vSwitch bridge, but it takes too long (minutes or hours) to do it with ovs-vsctl. How can I do it faster?

    A: If you add them one at a time with ovs-vsctl, it can take a long time to add thousands of ports to an Open vSwitch bridge. This is because every invocation of ovs-vsctl first reads the current configuration from OVSDB. As the number of ports grows, this starts to take an appreciable amount of time, and when it is repeated thousands of times the total time becomes significant.

    The solution is to add the ports in one invocation of ovs-vsctl (or a small number of them).

If there's a way we could query the API to get a delta of what the ovs db should look like, and does look like, then we could construct a much smaller statement to run rather than one per router.