retainAll (Function)

Function returns the updated list after retaining all the elements in the specified list.

Syntax

<OBJECT> list:retainAll(<OBJECT> list, <OBJECT> given.list)

Query Parameters

Name	Description	Default Value	Possible Data Types	Optional	Dynamic
list	The list that needs to be updated.		OBJECT	No	Yes
given.list	The list with all the elements that needs to retained.		OBJECT	No	Yes

Example 1

list:retainAll(stockSymbols, latestStockSymbols)

The list:retainAll(stockSymbols, latestStockSymbols) function retains only the elements in the stockSymbols list that are also present in the latestStockSymbols list. It then returns the updated stockSymbols list containing only these common elements.

Example 2

CREATE STREAM StockStream (symbols OBJECT, symbolsToRetain OBJECT);
CREATE SINK STREAM OutputStream (updatedSymbols OBJECT);

@info(name = 'RetainSymbols')
INSERT INTO OutputStream
SELECT list:retainAll(symbols, symbolsToRetain) AS updatedSymbols
FROM StockStream;

In this stream worker, the StockStream input stream is defined, which includes a list of stock symbols (symbols) and a list of symbols to retain (symbolsToRetain). The function list:retainAll(symbols, symbolsToRetain) operates on each event in the StockStream. It processes the symbols attribute from each event and retains only the elements that are also present in symbolsToRetain. The updated list is then aliased as updatedSymbols and inserted into the OutputStream. As a result, OutputStream contains updated lists from each event in the StockStream, with only common elements retained.