KEYS

Introduction and Use Case(s)

The KEYS command in Redis is used to find all keys matching a given pattern. It is particularly useful for debugging or discovering key names within your database, especially in development environments. However, it should be used sparingly in production due to its potential impact on performance.

Syntax

  1. KEYS pattern

Parameter Explanations

  • pattern: A glob-style pattern to match keys against. Patterns can include special characters:
    • * matches zero or more characters.
    • ? matches exactly one character.
    • [abc] matches any one of the characters inside the brackets.
    • [a-z] matches any character in the range.

Return Values

The KEYS command returns an array of keys that match the specified pattern.

Example:

  1. 1) "key1"
  2. 2) "key2"
  3. 3) "anotherkey"

If no keys match, it returns an empty list.

Code Examples

  1. dragonfly> SET key1 "value1"
  2. OK
  3. dragonfly> SET key2 "value2"
  4. OK
  5. dragonfly> SET anotherkey "value3"
  6. OK
  7. dragonfly> KEYS key*
  8. 1) "key1"
  9. 2) "key2"
  10. dragonfly> KEYS *key
  11. 1) "anotherkey"
  12. dragonfly> KEYS k?y1
  13. 1) "key1"

Best Practices

  • Use in Development: The KEYS command is best used in development or debugging scenarios due to its potential to cause high latency by scanning the entire keyspace.
  • Alternative Commands: In production, prefer using SCAN as it performs incremental iterations over the keyspace, being more memory and CPU efficient.
  • Pattern Specificity: Be specific with the patterns to minimize the number of keys returned and reduce overhead.

Common Mistakes

  • Large Databases: Running KEYS on a large dataset can block the server and degrade performance. Use it cautiously.
  • Misunderstanding Patterns: Ensure the correct use of wildcard characters in patterns to avoid unexpected results.

FAQs

How does KEYS impact Redis performance?

Using KEYS on a large dataset can block the Redis server, leading to increased latency and potential downtime for other operations. It scans the entire keyspace, which can be resource-intensive.

What are the alternatives to KEYS for safer production use?

The SCAN command is recommended for iterating through large datasets incrementally. It allows you to process keys in batches without blocking the server.