ZRANGEBYLEX

Introduction and Use Case(s)

The ZRANGEBYLEX command in Redis is used to return a range of members in a sorted set, where the elements are ordered lexicographically (alphabetically) by their value. This command is particularly useful for operations that need to fetch members from a sorted set within a specific lexicographical range, such as autocomplete suggestions or alphabetical filtering.

Syntax

ZRANGEBYLEX key min max [LIMIT offset count]

Parameter Explanations

• key: The name of the sorted set.
• min: The minimum value in the lexicographical range to include. Use - to represent the lowest possible string value.
• max: The maximum value in the lexicographical range to include. Use + to represent the highest possible string value.
• LIMIT offset count (optional): Limits the number of elements returned. offset specifies the number of elements to skip and count sets the maximum number of elements to return.

Return Values

Returns an array of elements in the specified range.

Examples:

• If there are matching elements: ["alpha", "beta", "gamma"]
• If no elements match: []

Code Examples

dragonfly> ZADD myzset 0 "alpha"
(integer) 1
dragonfly> ZADD myzset 0 "beta"
(integer) 1
dragonfly> ZADD myzset 0 "gamma"
(integer) 1
dragonfly> ZADD myzset 0 "delta"
(integer) 1
dragonfly> ZRANGEBYLEX myzset "[a" "[g"
1) "alpha"
2) "beta"
3) "delta"
dragonfly> ZRANGEBYLEX myzset "[a" "[d" LIMIT 1 2
1) "beta"
2) "delta"

Best Practices

• Ensure your elements are unique if they have the same score since ZRANGEBYLEX orders elements lexicographically when scores are equal.
• Utilize the LIMIT option to paginate through large sets efficiently.

Common Mistakes

• Confusing lexicographical order with numerical order. ZRANGEBYLEX does not sort by numerical value but by string comparison.
• Using incorrect syntax for min and max. Always include square brackets ([ ]) to indicate inclusive ranges.

FAQs

What happens if I use ( instead of [ in min or max?

Using ( indicates an exclusive range. For example, ZRANGEBYLEX myzset "(alpha" "[gamma" will exclude alpha from the results.

Can I use ZRANGEBYLEX on non-string elements?

No, ZRANGEBYLEX operates on string comparisons, so it isn’t suitable for non-string elements.