putIfAbsent (Function)
Function returns the updated map after adding the given key-value pair if key is absent.
Syntax
<OBJECT> map:putIfAbsent(<OBJECT> map, <INT|LONG|FLOAT|DOUBLE|BOOL|STRING> key, <INT|LONG|FLOAT|DOUBLE|BOOL|STRING> value)
Query Parameters
| Name | Description | Default Value | Possible Data Types | Optional | Dynamic |
|---|---|---|---|---|---|
| map | The map to which the value should be added. | OBJECT | No | Yes | |
| key | The key to be added. | INT LONG FLOAT DOUBLE BOOL STRING | No | Yes | |
| value | The value to be added. | INT LONG FLOAT DOUBLE BOOL STRING | No | Yes |
Example 1
map:putIfAbsent(stockDetails , 1234 , 'IBM')
The map:putIfAbsent(stockDetails, 1234, 'IBM') function checks the stockDetails map for the presence of the key 1234. If the key 1234 is not present in the map, it inserts the key-value pair 1234:'IBM' into the map. However, if the key 1234 already exists in the map, the map remains unchanged. The function returns the stockDetails map after the operation.
Example 2
CREATE STREAM StockInput (symbol string, price float, volume int);
CREATE SINK STREAM UpdatedStockData (symbol string, stockValues object);
@info(name = 'UpdateStockDetails')
INSERT INTO UpdatedStockData
SELECT symbol, map:putIfAbsent(map:create('price', price, 'volume', volume), 'price', price) AS stockValues
FROM StockInput;
In this example, the StockInput stream is created to provide input to the query, and the UpdatedStockData stream is created to collect the output.
The UpdateStockDetails query processes events from the StockInput stream, which contains stock details (symbol, price, and volume). It uses the map:putIfAbsent(map:create('price', price, 'volume', volume), 'price', price) function to create a map with 'price' and 'volume' keys and corresponding price and volume from the stream as values only if the 'price' key does not already exist.
The resulting map is then associated with the corresponding stock symbol and inserted into the UpdatedStockData stream. This way, the UpdatedStockData stream retains a unique set of stock details with each symbol mapped to a map of its 'price' and 'volume' from the StockInput stream.
In this stream worker, each event in StockInput generates a new map with 'price' and 'volume'. This is different from previous examples where the map was assumed to be an attribute of the stream or existed in a previous state. If you need to maintain the map across events, some form of state management or a different stream processing pattern may be necessary.