org.apache.flink.table.runtime.operators.window.slicing

Interface SliceSharedAssigner

All Superinterfaces:

Serializable, SliceAssigner

All Known Implementing Classes:

SliceAssigners.CumulativeSliceAssigner, SliceAssigners.HoppingSliceAssigner, SliceAssigners.SlicedSharedSliceAssigner

@Internal
public interface SliceSharedAssigner
extends SliceAssigner

A SliceAssigner which shares slices for windows, which means a window is divided into multiple slices and need to merge the slices into windows when emitting windows.

Classical window of SliceSharedAssigner is hopping window.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	SliceSharedAssigner.MergeCallback Callback to be used in mergeSlices(long, MergeCallback) for specifying which slices should be merged.

Method Summary

Modifier and Type	Method and Description
void	mergeSlices(long sliceEnd, SliceSharedAssigner.MergeCallback callback) Determines which slices (if any) should be merged.
Optional<Long>	nextTriggerWindow(long windowEnd, java.util.function.Supplier<Boolean> isWindowEmpty) Returns the optional end timestamp of next window which should be triggered.

Methods inherited from interface org.apache.flink.table.runtime.operators.window.slicing.SliceAssigner

assignSliceEnd, expiredSlices, getLastWindowEnd, getSliceEndInterval, getWindowStart, isEventTime

Method Detail

mergeSlices

void mergeSlices(long sliceEnd,
                 SliceSharedAssigner.MergeCallback callback)
          throws Exception

Determines which slices (if any) should be merged.

Parameters:

sliceEnd - the triggered slice, identified by end timestamp

callback - a callback that can be invoked to signal which slices should be merged.

Throws:

Exception

nextTriggerWindow

Optional<Long> nextTriggerWindow(long windowEnd,
                                 java.util.function.Supplier<Boolean> isWindowEmpty)

Returns the optional end timestamp of next window which should be triggered. Empty if no following window to trigger for now.

The purpose of this method is avoid register too many timers for each hopping and cumulative slice, e.g. HOP(1day, 10s) needs register 8640 timers for every slice. In order to improve this, we only register one timer for the next window. For hopping windows we don't register next window if current window is empty (i.e. no records in current window). That means we will have one more unnecessary window triggered for hopping windows if no elements arrives for a key for a long time. We will skip to emit window result for the triggered empty window, see SliceSharedWindowAggProcessor.fireWindow(Long).

Parameters:

windowEnd - the current triggered window, identified by end timestamp

isWindowEmpty - a supplier that can be invoked to get whether the triggered window is empty (i.e. no records in the window).