UUID is used to generate the global unique identifiers.
When the number of vertices reaches billions, using Hash Function to generate vid has a certain conflict probability. Therefore Nebula provides UUID Function to avoid vid conflicts in a large number of vertices. UUID Function is composed of the Murmur hash function and the current timestamp (in units of seconds).
Values generated with the UUID are stored in the Nebula Storage service in key-value mode. When called, it checks whether this key exists or conflicts. So the performance may be slower than hash.
Insert with UUID:
-- INSERT VERTEX player (name, age) VALUES hash("n0"):("n0", 13.0)
nebula> INSERT VERTEX player (name, age) VALUES uuid("n0"):("n0", 13.0)
-- INSERT EDGE like(likeness) VALUES hash("n0") -> hash("n1"): (90.0)
nebula> INSERT EDGE like(likeness) VALUES uuid("n0") -> uuid("n1"): (90.0)
Fetch with UUID:
nebula> FETCH PROP ON player uuid("n0") YIELD player.name, player.age
nebula> FETCH PROP ON like uuid("n0") -> uuid("n1")
Go with UUID:
nebula> GO FROM uuid("n0") OVER like