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ZREMRANGEBYLEX

Introduction​

In Dragonfly, as well as in Redis and Valkey, the ZREMRANGEBYLEX command is used to remove members from a sorted set, specifically those members whose names (lexicographically) fall within a specified range.

This command is most useful when you want to perform lexicographical operations with sorted sets, such as cleaning up or culling string-based range data within the sorted set.

Syntax​

ZREMRANGEBYLEX key min max
  • Time complexity: O(log(N)+M) with N being the number of elements in the sorted set and M the number of elements removed by the operation.
  • ACL categories: @write, @sortedset, @slow

Parameter Explanations​

  • key: The key of the sorted set to modify.
  • min and max:
    • The minimum and maximum lexicographical values to filter the members to be removed.
    • Valid min and max values must start with ( or [ to indicate exclusive or inclusive bounds respectively.
    • The + and - special values can be used to specify positive and negative infinity strings, respectively.

Return Values​

  • The command returns an integer indicating the number of members removed from the sorted set.

Code Examples​

Basic Example​

Remove members between alpha and delta inclusively:

dragonfly$> ZADD myzset 0 "alpha" 0 "bravo" 0 "charlie" 0 "delta" 0 "echo"
(integer) 5

dragonfly$> ZREMRANGEBYLEX myzset [alpha [delta
(integer) 4

dragonfly$> ZRANGE myzset 0 -1
1) "echo"

Exclusive Range Removal​

Remove an inclusive-to-exclusive range, excluding alpha but including delta:

dragonfly$> ZADD myzset 0 "alpha" 0 "bravo" 0 "charlie" 0 "delta" 0 "echo"
(integer) 5

dragonfly$> ZREMRANGEBYLEX myzset (alpha [delta
(integer) 3

dragonfly$> ZRANGE myzset 0 -1
1) "alpha"
2) "echo"

Removing All Members in a Lexicographical Range​

Remove everything up to delta inclusively:

dragonfly$> ZADD myzset 0 "alpha" 0 "bravo" 0 "charlie" 0 "delta" 0 "echo"
(integer) 5

dragonfly$> ZREMRANGEBYLEX myzset - [delta
(integer) 4

dragonfly$> ZRANGE myzset 0 -1
1) "echo"

Completely Clearing a Set With a Large Lexicographical Range​

Use ZREMRANGEBYLEX and the - and + special values to remove all members in a sorted set:

dragonfly$> ZADD myzset 0 alpha 0 bravo 0 charlie 0 delta 0 echo
(integer) 5

dragonfly$> ZREMRANGEBYLEX myzset - +
(integer) 5

dragonfly$> ZRANGE myzset 0 -1
(empty array)

Best Practices​

  • For optimal performance, ensure your use case logically fits lexicographical ordering. ZREMRANGEBYLEX works best when you're filtering or trimming sets based on string ranges.
  • If you're unsure about the lexicographical boundaries, use combinations of [ and ( as the inclusive/exclusive markers to adjust the range.

Common Mistakes​

  • Confusing inclusive and exclusive boundaries: Make sure you're clear whether you're including or excluding specific values when using [ and ( to define the range.
  • Using ZREMRANGEBYLEX on non-sorted set types will result in an error.

FAQs​

What happens if the key does not exist?​

If the key does not exist, ZREMRANGEBYLEX will return 0 as no members exist to be removed.

Can I use lexicographical ranges that extend beyond existing elements?​

Yes, you can specify broad ranges using - and + as lexicographical boundaries. If the range extends beyond the existing minimum or maximum members, no error occurs. The command will simply remove all elements within the included range based on existing members.