BITOP

Introduction

In Dragonfly, as well as in Redis and Valkey, the BITOP command is used to perform bitwise operations between multiple keys and store the result in a destination key. It supports operations like AND, OR, XOR, and NOT. This command is crucial for handling binary data and performing efficient bulk bitwise operations.

Syntax

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

Parameter Explanations

  • operation: The bitwise operation to be performed. It can be AND, OR, XOR, or NOT.
  • destkey: The key where the result of the bitwise operation will be stored.
  • key [key ...]: One or more keys containing string values on which the bitwise operation will be applied.

Return Values

Returns the size of the string stored in the destination key, measured in bytes.

Code Examples

Basic Example

Performing a basic bitwise AND operation between two keys:

  1. dragonfly> SET key1 "foobar"
  2. OK
  3. dragonfly> SET key2 "abcdef"
  4. OK
  5. dragonfly> BITOP AND result key1 key2
  6. (integer) 6
  7. dragonfly> GET result
  8. "\x60\x60\x04\x00\x00\x00"

Combining Multiple Keys with the OR Operation

Combining three keys using the OR operation:

  1. dragonfly> SET key1 "\x01"
  2. OK
  3. dragonfly> SET key2 "\x02"
  4. OK
  5. dragonfly> SET key3 "\x03"
  6. OK
  7. dragonfly> BITOP OR result key1 key2 key3
  8. (integer) 1
  9. dragonfly> GET result
  10. "\x03"

Using the XOR Operation

Using the XOR operation to combine two keys:

  1. dragonfly> SET key1 "\x0F"
  2. OK
  3. dragonfly> SET key2 "\xF0"
  4. OK
  5. dragonfly> BITOP XOR result key1 key2
  6. (integer) 1
  7. dragonfly> GET result
  8. "\xFF"

Using the NOT Operation

Performing the NOT operation on a single key:

  1. dragonfly> SET key1 "\xAA"  # 10101010 in binary
  2. OK
  3. dragonfly> BITOP NOT result key1
  4. (integer) 1
  5. dragonfly> GET result
  6. "\x55"  # 01010101 in binary (inverted bits)

Best Practices

  • Ensure the keys involved in the BITOP operation have values of the same length for predictable results.
  • Use the NOT operation with only one key, as this is the only unary operation in BITOP.

Common Mistakes

  • Using the NOT operation with more than one key will result in an error.
  • Performing operations on non-string data types can lead to unexpected results or errors.

FAQs

What happens if the keys have different lengths?

Redis pads the shorter strings with zero bytes to match the length of the longest string before performing the bitwise operation.

Can I use BITOP with empty keys?

Yes, but if all keys are empty, the result stored in the destination key will also be an empty string.