New options for SET from Redis 2.6.12

[debasishg]

Starting with Redis 2.6.12 SET supports a set of options that modify its behavior: EX seconds -- Set the specified expire time, in seconds. PX milliseconds -- Set the specified expire time, in milliseconds. NX -- Only set the key if it does not already exist. XX -- Only set the key if it already exist. Note: Since the SET command options can replace SETNX, SETEX, PSETEX, it is possible that in future versions of Redis these three commands will be deprecated and finally removed.