Thanks to Oran Agra (@oranagra) for reporting. Key extraction would not
work otherwise and it does not make sense to take wrong data in the
command table.
Currently this feature is only accessible via DEBUG for testing, since
otherwise depending on the instance configuration a given script works
or is broken, which is against the Redis philosophy.
By calling redis.replicate_commands(), the scripting engine of Redis
switches to commands replication instead of replicating whole scripts.
This is useful when the script execution is costly but only results in a
few writes performed to the dataset.
Morover, in this mode, it is possible to call functions with side
effects freely, since the script execution does not need to be
deterministic: anyway we'll capture the outcome from the point of view
of changes to the dataset.
In this mode math.random() returns different sequences at every call.
If redis.replicate_commnads() is not called before any other write, the
command returns false and sticks to whole scripts replication instead.
This new function is able to restart the server "in place". The current
Redis process executes the same executable it was executed with, using
the same arguments and configuration file.
