Fabian Hueske commented on FLINK-8601:

It's good to know that you're using this in production.

The design document suggests it's similar to MapState, ValueState, etc. because 
it uses the same terms (xyzState, xyzStateDescriptor, getxyzState, etc.). If 
this is not the same as the other states, I'd suggest to rename these concepts. 
I'd also add an Implementation section to the design document that explains 
which changes will be done.

Thanks, Fabian

> Introduce LinkedBloomFilterState for Approximate calculation and other 
> situations of performance optimization
> -------------------------------------------------------------------------------------------------------------
>                 Key: FLINK-8601
>                 URL: https://issues.apache.org/jira/browse/FLINK-8601
>             Project: Flink
>          Issue Type: New Feature
>          Components: Core, DataStream API
>    Affects Versions: 1.4.0
>            Reporter: Sihua Zhou
>            Assignee: Sihua Zhou
>            Priority: Major
> h3. Backgroud
> Bloom filter is useful in many situation, for example:
>  * 1. Approximate calculation: deduplication (eg: UV calculation)
>  * 2. Performance optimization: eg, [runtime filter 
> join|https://www.cloudera.com/documentation/enterprise/5-9-x/topics/impala_runtime_filtering.html]
> However, based on the current status provided by flink, it is hard to use the 
> bloom filter for the following reasons:
>  * 1. Serialization problem: Bloom filter status can be large (for example: 
> 100M), if implement it based on the RocksDB state, the state data will need 
> to be serialized each time it is queried and updated, and the performance 
> will be very poor.
>  * 2. Data skewed: Data in different key group can be skewed, and the 
> information of data skewed can not be accurately predicted before the program 
> is running. Therefore, it is impossible to determine how much resources bloom 
> filter should allocate. One way to do this is to allocate space needed for 
> the most skewed case, but this can lead to very serious waste of resources.
> h3. Requirement
> Therefore, I introduce the LinkedBloomFilterState for flink, which at least 
> need to meet the following features:
>  * 1. Support for changing Parallelism
>  * 2. Only serialize when necessary: when performing checkpoint
>  * 3. Can deal with data skew problem: users only need to specify a 
> LinkedBloomFilterState with the desired input, fpp, system will allocate 
> resource dynamic.
>  * 4. Do not conflict with other state: user can use KeyedState and 
> OperateState when using bloom filter state.
>  * 5. Support relax ttl (ie: the data survival time at least greater than the 
> specified time)
> Design doc:  [design 
> doc|https://docs.google.com/document/d/1yMCT2ogE0CtSjzRvldgi0ZPPxC791PpkVGkVeqaUUI8/edit?usp=sharing]

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