BF.SCANDUMP

Syntax
BF.SCANDUMP key iterator
Available in:
Redis Stack / Bloom 1.0.0
Time complexity:
O(n), where n is the capacity

Begins an incremental save of the Bloom filter.

This command is useful for large Bloom filters that cannot fit into the DUMP 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) to indicate completion.

Required arguments

key

is key name for a Bloom filter to save.

iterator

Iterator value; either 0 or the iterator from a previous invocation of this command

Return value

Returns one of these replies:

  • Array reply of Integer reply (Iterator) and [] (Data).

    The Iterator is passed as input to the next invocation of BF.SCANDUMP. If Iterator is 0, then it means iteration has completed.

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

  • [] on error (invalid arguments, key not found, wrong key type, etc.)

Examples

redis> BF.RESERVE bf 0.1 10
OK
redis> BF.ADD bf item1
1) (integer) 1
redis> BF.SCANDUMP bf 0
1) (integer) 1
2) "\x01\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x05\x00\x00\x00\x02\x00\x00\x00\b\x00\x00\x00\x00\x00\x00\x00@\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x9a\x99\x99\x99\x99\x99\xa9?J\xf7\xd4\x9e\xde\xf0\x18@\x05\x00\x00\x00\n\x00\x00\x00\x00\x00\x00\x00\x00"
redis> BF.SCANDUMP bf 1
1) (integer) 9
2) "\x01\b\x00\x80\x00\x04 \x00"
redis> BF.SCANDUMP bf 9
1) (integer) 0
2) ""
redis> DEL bf
(integer) 1
redis> BF.LOADCHUNK bf 1 "\x01\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x05\x00\x00\x00\x02\x00\x00\x00\b\x00\x00\x00\x00\x00\x00\x00@\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x9a\x99\x99\x99\x99\x99\xa9?J\xf7\xd4\x9e\xde\xf0\x18@\x05\x00\x00\x00\n\x00\x00\x00\x00\x00\x00\x00\x00"
OK
redis> BF.LOADCHUNK bf 9 "\x01\b\x00\x80\x00\x04 \x00"
OK
redis> BF.EXISTS bf item1
(integer) 1

Python code: 

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

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


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