BITOP

Introduction and Use Case(s)

The BITOP command in Redis performs bitwise operations between strings stored at specified keys and stores the result in a destination key. Typical use cases include manipulating binary data, performing fast aggregations on sets of flags, or implementing efficient counters.

Syntax

  1. BITOP operation destkey key [key ...]

Parameter Explanations

  • operation: The bitwise operation to perform. Possible values are:
    • AND: Perform a bitwise AND.
    • OR: Perform a bitwise OR.
    • XOR: Perform a bitwise XOR.
    • NOT: Perform a bitwise NOT (only takes one source key).
  • destkey: The key where the result will be stored.
  • key [key …]: One or more source keys which hold the strings to operate on.

Return Values

The BITOP command returns the length of the string stored in the destination key, which is equal to the length of the longest input string.

Examples

  1. dragonfly> SET key1 "\x01"
  2. OK
  3. dragonfly> SET key2 "\x01"
  4. OK
  5. dragonfly> BITOP AND destkey key1 key2
  6. (integer) 1
  7. dragonfly> GET destkey
  8. "\x01"
  10. dragonfly> SET key3 "\x02"
  11. OK
  12. dragonfly> BITOP OR destkey key1 key3
  13. (integer) 1
  14. dragonfly> GET destkey
  15. "\x03"
  17. dragonfly> BITOP XOR destkey key1 key3
  18. (integer) 1
  19. dragonfly> GET destkey
  20. "\x03"

Best Practices

  • Ensure that the keys involved contain binary-safe strings.
  • Use the smallest possible number of keys to avoid unnecessary memory usage and processing time.

Common Mistakes

  • Using non-existent keys in the operation can yield unexpected results since Redis treats missing keys as empty strings.
  • Incorrectly assuming BITOP NOT supports multiple keys; it only supports a single source key.

FAQs

What happens if the keys have different lengths?

Redis pads the shorter strings with zero-bytes so all strings are treated as having the same length as the longest string involved in the operation.

Can I perform BITOP on non-binary string values?

Yes, but make sure the values are interpreted as binary by your application logic. BITOP works at the byte level, regardless of the actual content.