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ZINCRBY

Increments the score of a member in a sorted set by the specified increment. If the member does not exist in the sorted set, it is added with the specified score as its initial value.

Syntax​

ZINCRBY key increment member

Parameters​

  • key: The name of the sorted set.
  • increment: The amount by which the score of the member should be increased. This can be a positive or negative floating-point number.
  • member: The member whose score should be incremented.

Details​

  • Available since: 1.2.0
  • Time complexity: O(log(N)) where N is the number of elements in the sorted set.
  • ACL categories: @write, @sortedset, @fast

If the member does not exist in the sorted set, ZINCRBY adds it with the specified increment as its score. If the member exists, the score is updated by adding the increment to the existing score.

Examples​

Basic Usage​

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

ZADD myzset 1 "member1" 2 "member2"

To increment the score of member1 by 3:

ZINCRBY myzset 3 "member1"

This will return:

"4"

To decrement the score of member2 by 1.5:

ZINCRBY myzset -1.5 "member2"

This will return:

"0.5"

Adding a New Member​

If the member does not exist, it will be added with the increment as its score:

ZINCRBY myzset 5 "member3"

This will return:

"5"

Edge Cases​

  • If the key does not exist, a new sorted set is created with the specified member and score.
  • If the increment is zero, the command simply returns the current score of the member without modifying the sorted set.
  • If the member's score becomes NaN (not a number) as a result of the increment, the operation fails.

RESP2/RESP3 Reply​

  • Bulk string reply: the new score of the member after the increment is applied.