[jira] [Created] (FLINK-8297) RocksDBListState stores whole list in single byte[]

[Shang Yuanchun (Jira)]

Jan Lukavský created FLINK-8297:
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             Summary: RocksDBListState stores whole list in single byte[]
                 Key: FLINK-8297
                 URL: https://issues.apache.org/jira/browse/FLINK-8297
             Project: Flink
          Issue Type: Improvement
          Components: Core
    Affects Versions: 1.3.2, 1.4.0
            Reporter: Jan Lukavský


RocksDBListState currently keeps whole list of data in single RocksDB key-value pair, which implies that the list actually must fit into memory. Larger lists are not supported and end up with OOME or other error. The RocksDBListState could be modified so that individual items in list are stored in separate keys in RocksDB and can then be iterated over. A simple implementation could reuse existing RocksDBMapState, with key as index to the list and a single RocksDBValueState keeping track of how many items has already been added to the list. Because this implementation might be less efficient in come cases, it would be good to make it opt-in by a construct like

{{new RocksDBStateBackend().enableLargeListsPerKey()}}



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