com.hazelcast.jet.core

## Class SlidingWindowPolicy

- java.lang.Object
- - com.hazelcast.jet.core.SlidingWindowPolicy

- All Implemented Interfaces:
    Serializable

      public class SlidingWindowPolicy
      extends Object
      implements Serializable

  Contains parameters that define a sliding/tumbling window over which Jet will apply an aggregate function. Internally, Jet computes the window by maintaining frames of size equal to the sliding step. It treats the frame as a "unit range" of timestamps which cannot be further divided and immediately applies the accumulating function to the items belonging to the same frame. This allows Jet to let go of the individual items' data, saving memory. The user-visible consequences of this are that the configured window length must be an integer multiple of the sliding step and that the memory requirements scale with the ratio between window size and the sliding step.

  A frame is labelled with its timestamp, which is the first timestamp value beyond the range covered by the frame. That timestamp denotes the exact moment on the event timeline where the frame was closed.

  See Also:
    Serialized Form

- - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `long` | `floorFrameTs(long timestamp)` Returns the highest frame timestamp less than or equal to the given timestamp.
    `long` | `frameOffset()` Returns the frame offset.
    `long` | `frameSize()` Returns the length of the frame (equal to the sliding step).
    `long` | `higherFrameTs(long timestamp)` Returns the lowest frame timestamp greater than the given timestamp.
    `boolean` | `isTumbling()` Tells whether this definition describes a tumbling window.
    `static SlidingWindowPolicy` | `slidingWinPolicy(long windowSize, long slideBy)` Returns the definition of a sliding window of length `windowSize` that slides by `slideBy`.
    `SlidingWindowPolicy` | `toTumblingByFrame()` Converts this definition to one defining a tumbling window of the same length as this definition's frame.
    `static SlidingWindowPolicy` | `tumblingWinPolicy(long windowSize)` Returns the definition of a tumbling window of length `windowSize`.
    `long` | `windowSize()` Returns the length of the window (the size of the timestamp range it covers).
    `SlidingWindowPolicy` | `withOffset(long offset)` Returns a new window definition where all the frames are shifted by the given offset.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Method Detail

    - #### frameSize

          public long frameSize()

      Returns the length of the frame (equal to the sliding step).

    - #### frameOffset

          public long frameOffset()

      Returns the frame offset. For example, with `frameLength = 10` and `frameOffset = 5` the frames will start at 5, 15, 25...

    - #### windowSize

          public long windowSize()

      Returns the length of the window (the size of the timestamp range it covers). It is an integer multiple of `frameSize()`.

    - #### isTumbling

          public boolean isTumbling()

      Tells whether this definition describes a tumbling window. Tumbling window is a special case of sliding window whose sliding step is equal to its size.

    - #### floorFrameTs

          public long floorFrameTs(long timestamp)

      Returns the highest frame timestamp less than or equal to the given timestamp. If there is no such `long` value, returns `Long.MIN_VALUE`.

    - #### higherFrameTs

          public long higherFrameTs(long timestamp)

      Returns the lowest frame timestamp greater than the given timestamp. If there is no such `long` value, returns `Long.MAX_VALUE`.

    - #### withOffset

          public SlidingWindowPolicy withOffset(long offset)

      Returns a new window definition where all the frames are shifted by the given offset. More formally, it specifies the value of the lowest non-negative frame timestamp.

      Given a tumbling window of `windowLength = 4`, with no offset the windows would cover the timestamps `..., [-4, 0), [0..4), ...` With `offset = 2` they will cover `..., [-2, 2), [2..6), ...`

    - #### toTumblingByFrame

          public SlidingWindowPolicy toTumblingByFrame()

      Converts this definition to one defining a tumbling window of the same length as this definition's frame.

    - #### slidingWinPolicy

          public static SlidingWindowPolicy slidingWinPolicy(long windowSize,
                                                             long slideBy)

      Returns the definition of a sliding window of length `windowSize` that slides by `slideBy`. Given `windowSize = 4` and `slideBy = 2`, the generated windows would cover timestamps `..., [-2, 2), [0..4), [2..6), [4..8), [6..10), ...`

      Since the window will be computed internally by maintaining `frames` of size equal to the sliding step, the configured window length must be an integer multiple of the sliding step.

      Parameters:
        `windowSize` - the length of the window, must be a multiple of `slideBy`
        `slideBy` - the amount to slide the window by

    - #### tumblingWinPolicy

          public static SlidingWindowPolicy tumblingWinPolicy(long windowSize)

      Returns the definition of a tumbling window of length `windowSize`. The tumbling window is a special case of the sliding window with `slideBy = windowSize`. Given `windowSize = 4`, the generated windows would cover timestamps `..., [-4, 0), [0..4), [4..8), ...`

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