Redis multi key and range operation

Multi key operation

MSET

Set multi key - value pairs

redis-cli>  MSET key1 value1 key2 value2

MGET

Get multi values from multi keys order by key

redis-cli> MGET key1 key2
redis-cli> [value1, value2]

GETRANGE, SETRANGE

Two indexes means between range [start, end].

redis-cli> SET name falcon
# from 0 index to 2 index (including 2)
redis-cli> GETRANGE 0 2 # "fal"

Why to use them?

It doesn’t look useful.
However, suppose we use traditional database table including multiple columns.
There’s some operations when we use update partial properties some rows.

• Fetch some column of a single row
• Update some column of a single row
• Create some rows with multiple columns

Especially, when using hashtable with encode value (ex. alphabet)

Example

INCR / DECR

These operations are supported for number type.
It seems that not necessary because we can implement using GET + SET

Why to use them?

1. Reduce network round trip
   It costs two round trip if GET + SET operations are used.
   INCR / DECR require single operation
2. Prevent from race condition
   Race condition would occur. when trying SET operation simultaneously by multiple servers.
   UsingINCR / DECR operation resolve this problem since the Redis is based on single thread.