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ZLEXCOUNT

Counts the number of members in a sorted set between a given lexicographical range.

Syntax​

ZLEXCOUNT key min max

Parameters​

  • key: The name of the sorted set.
  • min: The minimum lexicographical value (inclusive) of the range.
  • max: The maximum lexicographical value (inclusive) of the range.

Details​

  • Available since: 2.8.9
  • Time complexity: O(log(N)) with N being the number of elements in the sorted set.
  • ACL categories: @read, @sortedset, @fast

The ZLEXCOUNT command is used to count the number of elements in the sorted set stored at key with values lexicographically between min and max.

Special Range Syntax​

  • Inclusive Range: Specify the range with the value directly (e.g., min, max).
  • Exclusive Range: Prefix the value with an open parenthesis to exclude it from the range (e.g., (min, (max).
  • Unbounded Range: Use - for the minimum and + for the maximum to specify an open-ended range.

Examples​

Basic Usage​

Assume we have a sorted set called myzset with the following members:

ZADD myzset 0 "apple" 0 "banana" 0 "cherry" 0 "date" 0 "fig"

To count the number of members between "banana" and "date" (inclusive):

ZLEXCOUNT myzset [banana [date

This will return:

(integer) 3

Using Exclusive Range​

To count the number of members between "banana" (exclusive) and "date" (exclusive):

ZLEXCOUNT myzset (banana (date

This will return:

(integer) 1

Using Unbounded Range​

To count all members up to "cherry":

ZLEXCOUNT myzset - [cherry

This will return:

(integer) 3

Edge Cases​

  • If min is greater than max, ZLEXCOUNT returns 0.
  • If the key does not exist, ZLEXCOUNT returns 0.
  • If the key exists but is not a sorted set, an error is returned.

RESP2/RESP3 Reply​

  • Integer reply: the number of elements in the specified lexicographical range.