Time complexity: O(N) where N is the total number of keys in all databases
ACL categories: @keyspace, @write, @slow, @dangerous
Delete all the keys of all the existing databases, not just the currently selected one. This command never fails.
Note: an asynchronous
FLUSHALL command only deletes keys that were present at the time the command was invoked. Keys created during an asynchronous flush will be unaffected.