SLIDING_LENGTH()

A sliding length window that holds the last length events at a given time, and gets updated for each arrival and expiration.

Syntax

WINDOW SLIDING_LENGTH(length <INT>)

Query Parameters

Name	Description	Default Value	Possible Data Types	Optional	Dynamic
length	The number of events that should be included in a sliding length window.		INT	No	No

Example 1

CREATE STREAM cseEventStream (symbol string, price float, volume int);
CREATE WINDOW StockEventWindow (symbol string, price float, volume int) SLIDING_LENGTH(10) output all events;
CREATE SINK STREAM OutputStream (symbol string, price double);

@info(name = 'query0')
INSERT INTO StockEventWindow
FROM cseEventStream;

@info(name = 'query1')
INSERT all events INTO OutputStream 
SELECT symbol, sum(price) AS price
FROM StockEventWindow;

This query processes the last 10 events in a sliding manner.

Example 2

This example shows aggregating events based on event count in a sliding manner.

Stream Worker Code

CREATE STREAM TemperatureStream(sensorId string, temperature double);

CREATE SINK STREAM OverallTemperatureStream(avgTemperature double, maxTemperature double, numberOfEvents long);
CREATE SINK STREAM SensorIdTemperatureStream(sensorId string, avgTemperature double, maxTemperature double);

@info(name = 'Overall-analysis')
INSERT INTO OverallTemperatureStream
-- Calculate average, maximum, and count for `temperature` attribute.
SELECT avg(temperature) AS avgTemperature,
       max(temperature) AS maxTemperature,
       count() as numberOfEvents
-- Aggregate last `4` events in a sliding manner.
FROM TemperatureStream WINDOW SLIDING_LENGTH(4);


@info(name = 'SensorId-analysis')
INSERT INTO SensorIdTemperatureStream
SELECT sensorId,
-- Calculate average, and maximum for `temperature`, by grouping events by `sensorId`.
       avg(temperature) AS avgTemperature,
       max(temperature) AS maxTemperature
-- Aggregate last `5` events in a sliding manner.
FROM TemperatureStream WINDOW SLIDING_LENGTH(5)
GROUP BY sensorId
-- Output events only when `avgTemperature` is greater than or equal to `20.0`.
WHERE avgTemperature >= 20.0;

Sliding Event Count Aggregation Behavior

When events are sent to TemperatureStream, the following events are emitted at OverallTemperatureStream via the Overall-analysis query, and SensorIdTemperatureStream via the SensorId-analysis query.

Input to TemperatureStream	Output at OverallTemperatureStream	Output at SensorIdTemperatureStream
['1001', 19.0]	[19.0, 19.0, 1]	No events, as having condition not satisfied for '1001'.
['1002', 26.0]	[22.5, 26.0, 2]	['1002', 26.0, 26.0]
['1002', 24.0]	[23.0, 26.0, 3]	['1002', 25.5, 24.0]
['1001', 20.0]	[22.5, 26.0, 4]	No events, as having condition not satisfied for '1001'.
['1001', 21.0]	[22.75, 26.0, 4]	['1001', 20.0, 19.0]
['1001', 22.0]	[21.75, 24.0, 4]	['1001', 21.0, 20.0]