SLIDING_TIME()

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

Syntax

WINDOW SLIDING_TIME(time <INT|LONG|TIME>)

Query Parameters

Name	Description	Default Value	Possible Data Types	Optional	Dynamic
time	The sliding time period for which the window should hold events.		INT LONG TIME	No	No

Example 1

CREATE STREAM cseEventStream (symbol string, price float, volume int);
CREATE WINDOW cseEventWindow (symbol string, price float, volume int) SLIDING_TIME(20) output all events;
CREATE SINK STREAM OutputStream (symbol string, price double);

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

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

This query processes events that arrived within the last 20 milliseconds.

Example 2

This example shows aggregating events over time 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 ALL events INTO OverallTemperatureStream
-- Calculate average, maximum, and count for `temperature` attribute.
SELECT avg(temperature) AS avgTemperature,
       max(temperature) AS maxTemperature,
       count() AS numberOfEvents
-- Aggregate events over `1 minute` sliding window
FROM TemperatureStream WINDOW SLIDING_TIME(1 min);
-- Output when events are added, and removed (expired) from `window time()`.


@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 events over `30 seconds` sliding window
FROM TemperatureStream WINDOW SLIDING_TIME(30 sec)       
GROUP BY sensorId
-- Output events only when `avgTemperature` is greater than `20.0`.
WHERE avgTemperature > 20.0;
-- Output only when events are added to `window time()`.

Sliding Time 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.

Time	Input to TemperatureStream	Output at OverallTemperatureStream	Output at SensorIdTemperatureStream
9:00:00	['1001', 18.0]	[18.0, 18.0, 1]	No events, as having condition not satisfied.
9:00:10	['1002', 23.0]	[20.5, 23.0, 2]	['1002', 23.0, 23.0]
9:00:20	['1002', 22.0]	[21.0, 23.0, 3]	['1002', 22.5, 22.0]
9:00:40	-	-	No events, as expired events are not emitted.
9:00:50	-	-	No events, as expired events are not emitted.
9:00:00	-	[22.5, 23.0, 2]	-
9:01:10	['1001', 17.0]	[19.5, 22.0, 2]	-
9:01:20	-	[17.0, 17.0, 1]	-
9:02:10	-	[null, null, 0]	-