collect (Aggregate Function)

Collects multiple values to construct a list.

Syntax

<OBJECT> list:collect(<OBJECT|INT|LONG|FLOAT|DOUBLE|BOOL|STRING> value)
<OBJECT> list:collect(<OBJECT|INT|LONG|FLOAT|DOUBLE|BOOL|STRING> value, <BOOL> is.distinct)

Query Parameters

Name	Description	Default Value	Possible Data Types	Optional	Dynamic
value	Value of the list element		OBJECT INT LONG FLOAT DOUBLE BOOL STRING	No	Yes
is.distinct	If true only distinct elements are collected	false	BOOL	Yes	Yes

Example 1

INSERT INTO OutputStream
SELECT list:collect(symbol) AS stockSymbols
FROM StockStream WINDOW TUMBLING_LENGTH(10);

This example collects symbol attributes from the StockStream into a list. The collection happens within a tumbling window of 10 events. Once 10 events have occurred, the list of collected symbol attributes is output as stockSymbols in the OutputStream.

Example 2

INSERT INTO OutputStream
SELECT list:collect(symbol, true) AS distinctStockSymbols
FROM StockStream WINDOW TUMBLING_LENGTH(10);

This example operates within a tumbling window of 10 events from the StockStream. The list:collect(symbol, true) function collects only unique symbol attributes into a list. The resulting list of unique symbol attributes is output as distinctStockSymbols in the OutputStream.

Example 3

CREATE STREAM InputStockStream (symbol string, price double);
CREATE SINK STREAM OutputStockStream (collectedSymbols object);

@info(name = 'CollectSymbolsWorker')
INSERT INTO OutputStockStream
SELECT list:collect(symbol) AS collectedSymbols
FROM InputStockStream WINDOW TUMBLING_LENGTH(50);

Two streams are created in this stream worker example: InputStockStream for input data and OutputStockStream for output. The stream worker uses the list:collect(symbol) function within a tumbling window of 50 events from the InputStockStream. The function collects symbol attributes from these events into a list. When 50 events have occurred, the list of collected symbol attributes is output as collectedSymbols in the OutputStockStream.