Inbuilt Windows

Following are the supported inbuilt windows of Siddhi

Syntax	`<event> time(<int\|long\|time> windowTime)`
Extension Type	Window
Description	A sliding time window that holds events that arrived during the last `windowTime` period at a given time, and gets updated for each event arrival and expiry.
Parameter	`windowTime` : The sliding time period for which the window should hold events.
Return Type	Returns current and expired events.
Examples	`time(20`) for processing events that arrived within the last 20 milliseconds. `time(2 min)` for processing events that arrived within the last 2 minutes.

Syntax	`<event> timeBatch(<int\|long\|time> windowTime)`
Extension Type	Window
Description	A batch (tumbling) time window that holds events that arrive during `windowTime` periods, and gets updated for each `windowTime`.
Parameter	`windowTime` : The batch time period for which the window should hold events.
Return Type	Returns current and expired events.
Examples	`timeBatch(20)` for processing events that arrive every 20 milliseconds. `timeBatch(2 min)` for processing events that arrive every 2 minutes.

Syntax	`<event> length(<int> windowLength)`
Extension Type	Window
Description	A sliding length window that holds the last `windowLength` events at a given time, and gets updated for each arrival and expiry.
Parameter	`windowLength` : The number of events that should be included in a sliding length window.
Return Type	Returns current and expired events.
Examples	`length(10)` for processing the last 10 events. `length(200`) for processing the last 200 events.

Syntax	`<event> lengthBatch(<int> windowLength)`
Extension Type	Window
Description	A batch (tumbling) length window that holds a number of events specified as the `windowLength`. The window is updated each time a batch of events that equals the number specified as the `windowLength` arrives.
Parameter	`windowLength` : The number of events the window should tumble.
Return Type	Returns current and expired events.
Examples	`lengthBatch(10)` for processing 10 events as a batch. `lengthBatch(200)` for processing 200 events as a batch.

Syntax	`<event> externalTime(<long> timestamp, <int\|long\|time> windowTime)`
Extension Type	Window
Description	A sliding time window based on external time. It holds events that arrived during the last `windowTime` period from the external timestamp, and gets updated on every monotonically increasing timestamp.
Parameter	`windowTime` : The sliding time period for which the window should hold events.
Return Type	Returns current and expired events.
Examples	`externalTime(eventTime,20)` for processing events arrived within the last 20 milliseconds from the `eventTime` `externalTime(eventTimestamp, 2 min)` for processing events arrived within the last 2 minutes from the `eventTimestamp`

Syntax	`<event> cron(<string> cronExpression)`
Extension Type	Window
Description	This window returns events processed periodically as the output in time-repeating patterns, triggered based on time passing.
Parameter	`cronExpression`: cron expression that represents a time schedule.
Return Type	Returns current and expired events.
Examples	`cron('/5 * * * ?')` returns processed events as the output every 5 seconds.

Syntax	`<event> firstUnique(<string> attribute)`
Extension Type	Window
Description	First unique window processor keeps only the first events that are unique according to the given unique attribute.
Parameter	`attribute`: The attribute that should be checked for uniqueness.
Return Type	Returns current and expired events.
Examples	`firstUnique(ip)` returns the first event arriving for each unique `ip`.

Syntax	`<event> unique (<string> attribute )`
Extension Type	Window
Description	This window keeps only the latest events that are unique according to the given unique attribute.
Parameter	`attribute` : The attribute that should be checked for uniqueness.
Return Type	Returns current and expired events.
Examples	`unique(ip)` returns the latest event that arrives for each unique `ip`.

Syntax	`<event> sort(<int> windowLength)` `<event> sort(<int> windowLength, <string> attribute, <string> order)` `<event> sort(<int> windowLength, <string> attribute, <string> order, .. , <string> attributeN, <string> orderN)`
Extension Type	Window
Description	This window holds a batch of events that equal the number specified as the `windowLength` and sorts them in the given order.
Parameter	`attribute` : The attribute that should be checked for the order.
Return Type	Returns current and expired events.
Examples	`sort(5, price, 'asc')` keeps the events sorted by price in the ascending order. Therefore, at any given time, the window contains the 5 lowest prices.

Syntax	`<event> frequent(<int> eventCount)` `<event> frequent(<int> eventCount, <string> attribute, .. , <string> attributeN)`
Extension Type	Window
Description	This window returns the latest events with the most frequently occurred value for a given attribute(s). Frequency calculation for this window processor is based on Misra-Gries counting algorithm.
Parameter	`eventCount` : The number of most frequent events to be emitted to the stream.
Return Type	Returns current and expired events.
Examples	`frequent(2)` returns the 2 most frequent events. `frequent(2, cardNo)` returns the 2 latest events with the most frequently appeared card numbers.

Syntax	`<event> lossyFrequent(<double> supportThreshold, <double> errorBound)` `<event> lossyFrequent(<double> supportThreshold, <double> errorBound, <string> attribute, .. , <string> attributeN)`
Extension Type	Window
Description	This window identifies and returns all the events of which the current frequency exceeds the value specified for the `supportThreshold` parameter.
Parameters	`errorBound` : The error bound value. `attribute` : The attributes to group the events. If no attributes are given, the concatenation of all the attributes of the event is considered.
Return Type	Returns current and expired events.
Examples	`lossyFrequent(0.1, 0.01)` returns all the events of which the current frequency exceeds `0.1`, with an error bound of `0.01`. `lossyFrequent(0.3, 0.05, cardNo)` returns all the events of which the `cardNo` attributes frequency exceeds `0.3`, with an error bound of `0.05`.

Syntax	`<event> externalTimeBatch(<long> timestamp, <int\|long\|time> windowTime)`
Extension Type	Window
Description	A batch (tumbling) time window based on external time, that holds events arrived during `windowTime` periods, and gets updated for every `windowTime`.
Parameters	`timestamp` : The time which the window determines as current time and will act upon. The value of this parameter should be monotonically increasing. `windowTime` : The batch time period for which the window should hold events.
Return Type	Returns current and expired events.
Examples	`externalTimeBatch(eventTime,20)` for processing events that arrive every 20 milliseconds from the `eventTime`. `externalTimeBatch(eventTimestamp, 2 min`) for processing events that arrive every 2 minutes from the `eventTimestamp.`

Syntax	`<event> timeLength ( < int\|long\|time > windowTime, < int > windowLength )`
Extension Type	Window
Description	A sliding time window that, at a given time holds the last `windowLength` events that arrived during last `windowTime` period, and gets updated for every event arrival and expiry.
Parameters	`windowTime`: The sliding time period for which the window should hold events. `windowLength`: The number of events that should be be included in a sliding length window.
Return Type	Returns current and expired events.
Examples	`timeLength(20 sec, 10)` for processing the last 10 events that arrived within the last 20 seconds. `timeLength(2 min, 5)` for processing the last 5 events that arrived within the last 2 minutes.