Using Redis Sets

Jul 28, 2020

Learn how to use Redis sets, which are unordered and hold each item once, with SADD, SMEMBERS, SISMEMBER, SCARD and SINTER to intersect two sets.

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Sets have 2 main differences with lists:

Create a set using

SADD <setkey> <value>

The same command is used to add more items to the set.

Example:

SADD names "Flavio"
SADD names "Roger"
SADD names "Tony" "Mark" "Jane"

Get all the items in a set using SMEMBERS <setkey>:

Redis CLI showing SMEMBERS names command returning Roger, Flavio, and Syd

Find out if a value is in a set with SISMEMBER:

SISMEMBER names "Flavio"

Redis CLI showing SISMEMBER commands checking if Flavio and Roger are in the names set

To know how many items are in a set, use SCARD:

SCARD names

Get (without removing) an item from the set, randomly:

SRANDMEMBER names

Extract (and remove) an item from the set, casually ordered:

SPOP names

You can extract multiple items at once:

SPOP names 2

Remove an item from a set by value:

SREM names "Flavio"

Redis CLI showing SREM command removing Flavio from names set, then SMEMBERS showing Roger and Syd

Get the items contained in 2 different sets, exclusing elements only included in one with SINTER:

SINTER set1 set2

See all the sets commands here.

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