CF.SCANDUMP key iterator

Available in: Redis Stack

Time complexity: O(n), where n is the capacity

Begins an incremental save of the cuckoo filter. This is useful for large cuckoo filters which cannot fit into the normal SAVE and RESTORE model.

The first time this command is called, the value of iter should be 0. This command returns successive (iter, data) pairs until (0, NULL) indicates completion.


  • key: Name of the filter
  • iter: Iterator value. This is either 0, or the iterator from a previous invocation of this command


[] (Data). The Iterator is passed as input to the next invocation of SCANDUMP. If Iterator is 0, then it means iteration has completed.

The iterator-data pair should also be passed to LOADCHUNK when restoring the filter.


redis> CF.RESERVE cf 8
redis> CF.ADD cf item1
(integer) 1
redis> CF.SCANDUMP cf 0
1) (integer) 1
2) "\x01\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x02\x00\x14\x00\x01\x008\x9a\xe0\xd8\xc3\x7f\x00\x00"
redis> CF.SCANDUMP cf 1
1) (integer) 9
2) "\x00\x00\x00\x00\a\x00\x00\x00"
redis> CF.SCANDUMP cf 9
1) (integer) 0
2) (nil)
redis> CF.LOADCHUNK cf 1 "\x01\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x02\x00\x14\x00\x01\x008\x9a\xe0\xd8\xc3\x7f\x00\x00"
redis> CF.LOADCHUNK cf 9 "\x00\x00\x00\x00\a\x00\x00\x00"
redis> CF.EXISTS cf item1
(integer) 1

python code:

chunks = []
iter = 0
while True:
    iter, data = CF.SCANDUMP(key, iter)
    if iter == 0:
        chunks.append([iter, data])

# Load it back
for chunk in chunks:
    iter, data = chunk
    CF.LOADCHUNK(key, iter, data)