Redis store key without a value

Question

When using the Redis expire commands like SETEX and TTL, there are scenarios in which there is no need for the key to hold a value at all, because the time to live acts as such.

However, Redis requires any key to have a value.

What would be the most reasonable value to use - if you don't ever want to read it?

score 61 · Answer 1 · answered Sep 04 '14 at 14:28

61

Who said that you should actually store anything in redis key?

Empty string "" is a perfectly valid value for a redis key, and it's a shortest possible one:

> SET foo ""
OK
> GET foo
""
> BITCOUNT foo
(integer) 0

answered Sep 04 '14 at 14:28

Leonid Beschastny

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When using the StackExchange Redis client this can be detected by seeing that a RedisValue.IsNull is false but IsNullOrEmpty is true (what an api!). – Svend Jul 09 '18 at 09:51
this should be more clear that it is the value for a key 'foo' and not setting key to "" – botbot Jul 28 '19 at 10:15
3

When examined with `MEMORY USAGE [key]`, a value of `0` has a smaller footprint than an empty string. [See the answer below.](https://stackoverflow.com/a/59292672) – Daniel Mar 12 '21 at 09:02

score 19 · Accepted Answer · answered Dec 11 '19 at 19:21

19

I would avoid using "". How about simple 0 ?

127.0.0.1:6379> set akey 0
OK
127.0.0.1:6379> memory usage akey
(integer) 48
127.0.0.1:6379> set akey ""
OK
127.0.0.1:6379> memory usage akey
(integer) 50
127.0.0.1:6379>

answered Dec 11 '19 at 19:21

null

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I think this is probably a better answer, in terms of real memory consumption. – Nathan Lutterman May 22 '20 at 03:14
2

A `0` has a greater likelihood of being a _useful_ value, whereas `""` already essentially means empty or nothing. `""` is better when dealing with integer values is a possibility (or becomes a possibility in the future). – AlexPi Sep 30 '22 at 19:20

score 9 · Answer 3 · answered Sep 04 '14 at 14:17

9

I would store one byte of data that could also be broadly interpreted as "truthy", such as the ASCII character 1.

answered Sep 04 '14 at 14:17

platforms

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score 0 · Answer 4 · answered Aug 28 '14 at 21:03

0

Do you serialize everything coming to and from redis, yourself? If so, you may consider using a sentinel value (like a NONE constant, etc.) which is set to something like 'None'.

answered Aug 28 '14 at 21:03

Greg M. Krsak

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Redis store key without a value

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