What's New in Redis 6.2!

This repository contains example data and exercises to accompany the Redis University "What's New in Redis 6.2" Head in the Corner video on YouTube.

Redis 6.2 introduced lots of new features and enhancements. In the video and this accompanying repository, we'll look at five of them:

1. New options for the SET command.
2. New alternatives to the GET command.
3. A new trimming strategy for Redis Streams.
4. The new HRANDFIELD command.
5. The new SMISMEMBER command.

If you enjoyed this video and would like to see more, be sure to subscribe to our YouTube channel. We're also on Discord, join us for ongoing Redis chat!

Setup and Load Sample Data

To try out the new Redis 6.2 features covered in the video, use Docker and docker-compose to start a Redis server like so:

$ git clone https://github.com/redislabs-training/hitc-new-in-redis-62.git
$ cd hitc-new-in-redis-62
$ docker-compose up -d
Creating network "hitc-new-in-redis-62_default" with the default driver
Creating hitc_redis ... done
$

Load the sample data from the shell in the container:

$ docker exec -it hitc_redis sh
/data # /sampledata/load_all.sh
(integer) 0
OK
OK
(integer) 0
OK
OK
OK
OK
OK
OK
OK
OK
OK
(integer) 0
OK
OK
(integer) 0
"1617307200000-0"
"1617307231000-0"
"1617307262000-0"
...
(integer) 6
# exit
$

Use the redis-cli in the container to enter Redis commands and make sure you have Redis 6.2 or later:

$ docker exec -it hitc_redis redis-cli
127.0.0.1:6379> info server
...
redis_version:6.2.1
...

Exit redis-cli using the quit command:

127.0.0.1:6379> quit
$

To stop the container when you are done with it:

$ docker-compose down

1) Strings: New Options for the SET Command

Redis 6.2 adds GET, EXAT and PXAT options to the SET command. The GET option retrieves any previous value while setting a new one:

127.0.0.1:6379> set favoriteflavor "Mint Choc Chip"
OK
127.0.0.1:6379> set favoriteflavor "Vanilla Bean" get
"Mint Choc Chip"
127.0.0.1:6379> get favoriteflavor
"Vanilla Bean"

The EXAT option allows us to specify a timestamp at which the key should expire, while also setting the key's value:

127.0.0.1:6379> set couponcode halfoff exat 1640937600
OK
127.0.0.1:6379> ttl couponcode
(integer) 21387890

PXAT works in the same way, but takes a millisecond timestamp.

2) Strings: New Alternatives to the GET Command

The new GETEX and GETDEL commands were added in Redis 6.2. GETEX gets the value of a key and sets an expiry on it at the same time, GETDEL gets the value of a key and deletes it.

For example, let's store a coupon code in a Redis key and use GETDEL so that only the first person to redeem it gets it:

127.0.0.1:6379> set onetimecoupon halfoff
OK
127.0.0.1:6379> getdel onetimecoupon
"halfoff"
127.0.0.1:6379> getdel onetimecoupon
(nil)

Or let's start a 2 hour TTL on another coupon when it is retrieved:

127.0.0.1:6379> set limitedtimecoupon freeicecream
OK
127.0.0.1:6379> getex limitedtimecoupon ex 7200
"freeicecream"
127.0.0.1:6379> ttl limitedtimecoupon
(integer) 7194

GETEX also accepts the PX option to set expiry in milliseconds, as well as EXAT when setting expiry to a specific timestamp and PXAT for a millisecond timestamp.

3) Streams: MINID Trimming Strategy

Redis 6.2 introduced a new trimming strategy for managing the entries in a Redis Stream. Previously, you could use the MAXLEN modifier to the XADD and XTRIM commands, which would remove the oldest entries from a stream until the stream's length was a specified number of entries. This strategy also supported trimming to approximately the specified number of entries for greater performance.

Redis 6.2 adds a second trimming strategy called MINID. This allows us to trim the stream such that any entry whose ID is less than the one provided is removed. Given that the default ID for a Redis stream entry is a timestamp, we now have the ability to trim streams to a given period in time which is more in line with how consumers read from them.

The sample data contains a stream named redemptions which has data concerning our ice cream coupon redemptions. You can use this to try out the MINID trimming strategy with the sample data provided.

Discover the range of timestamps in the stream:

127.0.0.1:6379> xrange redemptions - + count 1
1) 1) "1617307200000-0"
   2) 1) "couponcode"
      2) "weekendsale"
      3) "userid"
      4) "6935"
127.0.0.1:6379> xrevrange redemptions + - count 1
1) 1) "1617314919000-0"
   2) 1) "couponcode"
      2) "weekendsale"
      3) "userid"
      4) "5577"

Check the initial length of the stream:

127.0.0.1:6379> xlen redemptions
(integer) 250

Trim the stream so that all remaining IDs are equal to or greater than the one provided (removes 16 entries):

127.0.0.1:6379> xtrim redemptions minid 1617307696000
(integer) 16
127.0.0.1:6379> xlen redemptions
(integer) 234

Check that new end of the stream:

127.0.0.1:6379> xrange redemptions - + count 1
1) 1) "1617307696000-0"
   2) 1) "couponcode"
      2) "weekendsale"
      3) "userid"
      4) "529"

Add a new entry while also trimming the stream to a new minimum ID:

127.0.0.1:6379> xadd redemptions minid 1617307851000 * couponcode weekendsale userid 9002
"1619559177427-0"
127.0.0.1:6379> xlen redemptions
(integer) 230

4) Hashes: HRANDFIELD Command

The new HRANDFIELD command picks one or more random field names from a Redis Hash. It returns the field name, and optionally the value too. When asking for multiple fields, you can specify whether or not they all have to be unique.

Try this out with some take out restaurant examples... Look at all the entrees:

127.0.0.1:6379> hgetall entrees
 1) "10"
 2) "Szechuan Shredded Beef"
 3) "11"
 4) "King Prawns with Cashew Nuts"
 5) "12"
 6) "Roast Duck with Plum Sauce"
 7) "13"
 8) "Grilled Lemon Chicken"
 9) "14"
10) "Chicken with Pineapple"
11) "15"
12) "Beef with Broccoli"
13) "16"
14) "Malaysian Chicken Curry"
15) "17"
16) "House Special Chow Mein"
17) "18"
18) "Mushroom Fried Rice"
19) "19"
20) "Fried Mushrooms with Black Bean Sauce"
21) "20"
22) "Singapore Fried Rice"

Get a random entree number:

127.0.0.1:6379> hrandfield entrees 1
1) "17"

Get two random entree numbers along with the names of the dishes:

127.0.0.1:6379> hrandfield entrees 2 withvalues
1) "14"
2) "Chicken with Pineapple"
3) "19"
4) "Fried Mushrooms with Black Bean Sauce"

Using -2, we can say we want 2 random entries but its OK if they're the same... try this a few times until you get 2 x the same dish :)

127.0.0.1:6379> hrandfield entrees -2 withvalues
1) "15"
2) "Beef with Broccoli"
3) "15"
4) "Beef with Broccoli"

5) Sets: SMISMEMBER Command

The new SMISMEMBER command allows us to check set membership for multiple members at once, rather than having to use SISMEMBER for each individually. Try this out with the lottery example in the sample data, check if my six numbers won!:

127.0.0.1:6379> smembers winninglotto
1) "3"
2) "5"
3) "19"
4) "27"
5) "33"
6) "56"
127.0.0.1:6379> smismember winninglotto 1 3 7 19 22 33
1) (integer) 0
2) (integer) 1
3) (integer) 0
4) (integer) 1
5) (integer) 0
6) (integer) 1

SMISMEMBER returns 1 if a match is found and 0 otherwise.

Resources

Useful links to help you learn more about Redis:

• Redis 6.2 Release Blog post at redis.com
• Redis 6.2 GEOSEARCH command repo
• Redis 6.2 GEOSEARCH command video
• Redis Enterprise Cloud - free 30Mb starter tier
• Redis University
• redis.io
• Redis Discord
• Redis Developer Relations Live Streaming Schedule
• Redis YouTube Channel
• Redis Twitch Channel
• Redis Developer
• Redis