Skip to main content

ZINTERCARD

Returns the number of members in the intersection of multiple sorted sets.

Syntax​

ZINTERCARD numkeys key [key ...] [LIMIT limit]

Parameters​

  • numkeys: The number of sorted sets involved in the intersection.
  • key: The name of each sorted set involved in the operation.
  • LIMIT: Optional. Specifies a limit on the number of members to calculate in the intersection. If the intersection cardinality reaches this limit, the command returns the limit as the result.

Details​

  • Available since: 7.0.0
  • Time complexity: O(N*K) worst case where N is the size of the smallest input sorted set and K is the number of input sorted sets.
  • ACL categories: @read, @sortedset, @slow

The ZINTERCARD command is used to quickly obtain the cardinality (number of members) of the intersection of the specified sorted sets without actually retrieving the intersecting members.

Examples​

Basic Usage​

Assume we have three sorted sets:

ZADD set1 1 "a" 2 "b" 3 "c"
ZADD set2 1 "b" 2 "c" 3 "d"
ZADD set3 1 "c" 2 "d" 3 "e"

To find the number of members in the intersection of these sets:

ZINTERCARD 3 set1 set2 set3

This will return:

(integer) 1

Using the LIMIT Option​

To limit the intersection calculation to 2 members:

ZINTERCARD 3 set1 set2 set3 LIMIT 2

This will return:

(integer) 1

The command stops the computation if the intersection cardinality reaches the specified limit.

Edge Cases​

  • If the intersection is empty, ZINTERCARD will return 0.
  • If the key does not exist, it is treated as an empty set.
  • If any of the keys refer to non-sorted set data types, an error is returned.

RESP2/RESP3 Reply​

  • Integer reply: the number of members in the intersection of the specified sorted sets.