Username or ID for keys in Redis

Question

I was wondering what the benefits of using user IDs were rather than just using the unique username for the keys.

• user:USERNAME => {password: HASH, age: 45}
• user:0 => {username: USERNAME, password: HASH, age: 45}

Note that I would wish to lookup users by name, therefore requiring a second set of key-values to relate usernames to IDs.

Given that every username is unique and has to be alphanumeric is there any particular reason why it may be beneficial to use the ID system.

The main reason I ask this is because I primarily used IDs as they decreased lookup times in my database, especially when the database was normalized in some way. But Redis doesn't gain this benefit and so I wondered what other reasons there may be to use user IDs instead of just the usernames.

Thanks for any help,

Pluckerpluck

p.s. Due to the way Redis handles hashes I am very actually unsure about the memory differences between the two methods so information on this may be good, though I may go and test this myself later.

Answer 1

Does not matter in the use case you defined, but using integer user ids has other advantages.

Sooner or later, you would want to reference user ids in other objects. For example, "Friends of user pluckerpluck". To model that, you'd have two alternatives -

friendsof:pluckerpluck -> SET{tom, dick, harry}

VS

friendsof:1 --> SET{2, 3, 4}

The former approach uses a regular Hash table to store the elements, and uses a lot of memory. The latter approach uses an integer array and is extremely memory efficient.

This special encoding for sets of integers is called IntSet. You can control the behaviour of Redis using the property set-max-intset-entries

# Sets have a special encoding in just one case: when a set is composed
# of just strings that happens to be integers in radix 10 in the range
# of 64 bit signed integers.
# The following configuration setting sets the limit in the size of the
# set in order to use this special memory saving encoding.
set-max-intset-entries 512