[Feature Request]: Add hotkey shuffle/fanout support to BeamSQL

[Polber]

What would you like to happen?

Currently BeamSQL does not have a way to reshuffle data that contains hotkeys during sub-transforms. For example, if a pipeline performs a JOIN operation as part of a SQLTransform, there is a good chance that a given key contains a disproportionate amount of data when it is fed into the GroupByKey that is performed as part of the expanded JOIN operation. Adding hotkey detection and reshuffling/fanout similar to Combine.PerKey.withHotKeyFanout should greatly increase performance.

Issue Priority

Priority: 2 (default / most feature requests should be filed as P2)

Issue Components

• Component: Python SDK
• Component: Java SDK
• Component: Go SDK
• Component: Typescript SDK
• Component: IO connector
• Component: Beam examples
• Component: Beam playground
• Component: Beam katas
• Component: Website
• Component: Spark Runner
• Component: Flink Runner
• Component: Samza Runner
• Component: Twister2 Runner
• Component: Hazelcast Jet Runner
• Component: Google Cloud Dataflow Runner