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SUNIONSTORE

Computes the union of multiple sets and stores the resulting set in a new key.

Syntax​

SUNIONSTORE destination key [key ...]

Parameters​

  • destination: The key where the result of the union operation will be stored.
  • key: One or more keys representing the sets to be combined.

Details​

  • Available since: 1.0.0
  • Time complexity: O(N) where N is the total number of elements in all the sets.
  • ACL categories: @write, @set, @slow

The SUNIONSTORE command computes the union of multiple sets and stores the resulting set in the key specified by destination. This operation overwrites any existing value at the destination key.

Examples​

Union of Two Sets​

Assume we have the following sets:

SADD set1 "a" "b" "c"
SADD set2 "b" "c" "d"

To compute the union of set1 and set2 and store it in resultset:

SUNIONSTORE resultset set1 set2

After running this command, the resultset key will contain:

S Members of set1 and set2:
1) "a"
2) "b"
3) "c"
4) "d"

Union of Multiple Sets​

Assume we have additional sets:

SADD set3 "e" "f"
SADD set4 "g" "h"

To compute the union of set1, set2, set3, and set4 and store it in allsets:

SUNIONSTORE allsets set1 set2 set3 set4

After running this command, the allsets key will contain:

S Members of set1, set2, set3, and set4:
1) "a"
2) "b"
3) "c"
4) "d"
5) "e"
6) "f"
7) "g"
8) "h"

Edge Cases​

  • If any of the source keys do not exist, they are treated as empty sets.
  • If destination already exists, it will be overwritten with the result of the union operation.
  • If no source keys are specified, SUNIONSTORE creates an empty set at destination.

RESP2/RESP3 Reply​

  • Integer reply: the number of elements in the resulting set stored at destination.