0fc4aaa71c
This PR adds the ability to perform aggregations inside of a `ContinuousQuery`. In order to implement this feature, the planning of aggregation has augmented with a new `StatefulAggregationStrategy`. Unlike batch aggregation, stateful-aggregation uses the `StateStore` (introduced in #11645) to persist the results of partial aggregation across different invocations. The resulting physical plan performs the aggregation using the following progression: - Partial Aggregation - Shuffle - Partial Merge (now there is at most 1 tuple per group) - StateStoreRestore (now there is 1 tuple from this batch + optionally one from the previous) - Partial Merge (now there is at most 1 tuple per group) - StateStoreSave (saves the tuple for the next batch) - Complete (output the current result of the aggregation) The following refactoring was also performed to allow us to plug into existing code: - The get/put implementation is taken from #12013 - The logic for breaking down and de-duping the physical execution of aggregation has been move into a new pattern `PhysicalAggregation` - The `AttributeReference` used to identify the result of an `AggregateFunction` as been moved into the `AggregateExpression` container. This change moves the reference into the same object as the other intermediate references used in aggregation and eliminates the need to pass around a `Map[(AggregateFunction, Boolean), Attribute]`. Further clean up (using a different aggregation container for logical/physical plans) is deferred to a followup. - Some planning logic is moved from the `SessionState` into the `QueryExecution` to make it easier to override in the streaming case. - The ability to write a `StreamTest` that checks only the output of the last batch has been added to simulate the future addition of output modes. Author: Michael Armbrust <michael@databricks.com> Closes #12048 from marmbrus/statefulAgg. |
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