Myracle opened a new pull request, #27533:
URL: https://github.com/apache/flink/pull/27533
## What is the purpose of the change
This pull request adds support for `emit-only-on-update` mode in the
CUMULATE window Table-Valued Function (TVF). When enabled, the CUMULATE window
will skip emitting results for step intervals where no new data has arrived,
reducing unnecessary duplicate outputs in sparse data streams. This
optimization is particularly useful for scenarios where data arrives
intermittently, as it avoids repeatedly outputting the same aggregation results.
## Brief change log
- Added a new optional boolean parameter `emitOnlyOnUpdate` (6th parameter)
to the `CUMULATE` window TVF SQL function
- Extended `CumulativeWindowSpec` to support the new `emitOnlyOnUpdate`
field with JSON serialization/deserialization
- Modified `CumulativeSliceAssigner` in `SliceAssigners` to track and expose
the `emitOnlyOnUpdate` configuration
- Updated `SliceSharedSyncStateWindowAggProcessor` and
`AsyncStateSliceSharedWindowAggProcessor` to implement the emit-only-on-update
logic by tracking whether new data arrived in the current step interval
- Improved `SqlWindowTableFunction.checkIntervalOperands()` to skip boolean
parameters dynamically instead of hardcoded parameter count check
- Added integration tests for the new feature with various scenarios
(enabled/disabled comparison, multi-key grouping)
- Updated documentation (both English and Chinese) with parameter
description and usage examples
## Verifying this change
This change added tests and can be verified as follows:
- Added `testCumulateWindowWithEmitOnlyOnUpdate()` integration test that
verifies windows are skipped when no new data arrives in a step interval
- Added `testCumulateWindowWithEmitOnlyOnUpdateDisabled()` integration test
that verifies default behavior (emitOnlyOnUpdate=false) outputs all cumulating
windows
- Added `testCumulateWindowWithEmitOnlyOnUpdateAndMultiKey()` integration
test that verifies the feature works correctly with multiple grouping keys
- Manually verified the change by comparing output row counts between
`emitOnlyOnUpdate=true` and `emitOnlyOnUpdate=false` modes
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): **no**
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: **no**
- The serializers: **no** (only added new optional field with
backward-compatible JSON deserialization)
- The runtime per-record code paths (performance sensitive): **yes** (added
a boolean check in the window aggregation output path, but the overhead is
minimal)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Kubernetes/Yarn, ZooKeeper: **no**
- The S3 file system connector: **no**
## Documentation
- Does this pull request introduce a new feature? **yes**
- If yes, how is the feature documented? **docs / JavaDocs**
- Updated `docs/content/docs/dev/table/sql/queries/window-tvf.md` (English)
- Updated `docs/content.zh/docs/dev/table/sql/queries/window-tvf.md`
(Chinese)
- Added JavaDoc comments for the new parameter in
`SqlCumulateTableFunction.java`
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