[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PROPOSAL] Introduce Elastic Bloom Filter For Flink


I did a survey of the variants of Bloom Filter and the Cuckoo filter these days. Finally, I found 3 of them maybe adaptable for our purpose.

1. standard bloom filter (which we have implemented base on this and used it on production with a good experience)
2. cuckoo filter, also a very good filter which is a space-efficient data structures and support fast query(even faster then BF, but the insert maybe a little slower than BF), addtional it support delete() operation.
3. count bloom filter, a variant of BF, it supports delete()operation, but need to cost 4-5x memory than the standard bloom filter(so, I'm not sure whether it's adaptable in practice).

Anyway, these filters are just the smallest storage unit in this "Elastic Bloom Filter", we can define a general interface, and provide different implementation of "storage unit"  base on different filter if we want. Maybe I should change the PROPOSAL name to the "Introduce Elastic Filter For Flink", the ideal of approach that I outlined in the doc is very similar to the paper "Optimization and Applications of Dynamic Bloom Filters(http://ijarcs.info/index.php/Ijarcs/article/viewFile/826/814)"(compare to the paper, the approach I outlined could have a better query performance and also support the RELAXED TTL), maybe it can help to understand the desgin doc. Looking forward any feedback!

Best, Sihua
On 05/24/2018 10:36,sihua zhou<summerleafs@xxxxxxx> wrote:
Thanks for your suggestions @Elias! I have a brief look at "Cuckoo Filter" and "Golumb Compressed Sequence", my first sensation is that maybe "Golumc Compressed Sequence" is not a good choose, because it seems to require non-constant lookup time, but Cuckoo Filter maybe a good choose, I should definitely have a deeper look at it.

Beside, to me, all of this filters seems to a "variant" of the bloom filter(which is the smallest unit to store data in the current desgin), the main challenge for introducing BF into flink is the data skewed(which is common phenomenon on production) problem, could you maybe also have a look at the solution that I posted on the google doc https://docs.google.com/document/d/17UY5RZ1mq--hPzFx-LfBjCAw_kkoIrI9KHovXWkxNYY/edit?usp=sharing for this problem, It would be nice if you could give us some advice on that.

Best, Sihua

On 05/24/2018 07:21,Elias Levy<fearsome.lucidity@xxxxxxxxx> wrote:
I would suggest you consider an alternative data structures: a Cuckoo
Filter or a Golumb Compressed Sequence.

The GCS data structure was introduced in Cache-, Hash- and Space-Efficient
Bloom Filters
<http://algo2.iti.kit.edu/documents/cacheefficientbloomfilters-jea.pdf> by
F. Putze, P. Sanders, and J. Singler.  See section 4.

We should discuss which exact implementation of bloom filters are the best
@Fabian: There are also implementations of bloom filters that use counting
and therefore support
deletes, but obviously this comes at the cost of a potentially higher
space consumption.

Am 23.05.2018 um 11:29 schrieb Fabian Hueske <fhueske@xxxxxxxxx>:
IMO, such a feature would be very interesting. However, my concerns with
Bloom Filter
is that they are insert-only data structures, i.e., it is not possible to
remove keys once
they were added. This might render the filter useless over time.
In a different thread (see discussion in FLINK-8918 [1]), you mentioned
that the Bloom
Filters would be growing.
If we keep them in memory, how can we prevent them from exceeding memory
boundaries over