BITOP AND | OR | XOR | NOT destkey key
Available since
Time complexity
ACL categories
@write, @bitmap, @slow

Perform a bitwise operation between multiple keys (containing string values) and store the result in the destination key.

The BITOP command supports four bitwise operations: AND, OR, XOR and NOT, thus the valid forms to call the command are:

  • BITOP AND destkey srckey1 srckey2 srckey3 ... srckeyN
  • BITOP OR destkey srckey1 srckey2 srckey3 ... srckeyN
  • BITOP XOR destkey srckey1 srckey2 srckey3 ... srckeyN
  • BITOP NOT destkey srckey

As you can see NOT is special as it only takes an input key, because it performs inversion of bits so it only makes sense as a unary operator.

The result of the operation is always stored at destkey.

Handling of strings with different lengths #

When an operation is performed between strings having different lengths, all the strings shorter than the longest string in the set are treated as if they were zero-padded up to the length of the longest string.

The same holds true for non-existent keys, that are considered as a stream of zero bytes up to the length of the longest string.

Examples #

SET key1 "foobar"
SET key2 "abcdef"
BITOP AND dest key1 key2
GET dest

Pattern: real time metrics using bitmaps #

BITOP is a good complement to the pattern documented in the BITCOUNT command documentation. Different bitmaps can be combined in order to obtain a target bitmap where the population counting operation is performed.

See the article called “Fast easy realtime metrics using Redict bitmaps” for an interesting use cases.

Performance considerations #

BITOP is a potentially slow command as it runs in O(N) time. Care should be taken when running it against long input strings.

For real-time metrics and statistics involving large inputs a good approach is to use a replica (with replica-read-only option enabled) where the bit-wise operations are performed to avoid blocking the master instance.

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