merge (Aggregate Function)
Collect multiple maps to merge as a single map. Only distinct keys are collected. If a duplicate key arrives, then it overrides the old value.
Syntax
<OBJECT> map:merge(<OBJECT> map)
Query Parameters
| Name | Description | Default Value | Possible Data Types | Optional | Dynamic |
|---|---|---|---|---|---|
| map | Maps to be collected | OBJECT | No | Yes |
Example 1
map:merge(map)
The map:merge(map) function takes a collection of maps and merges them into a single map. If there are conflicting keys, the function will overwrite the values with the ones from the latest map.
Example 2
CREATE STREAM StockInputStream (stockMap object);
CREATE SINK STREAM MergedStockStream (mergedStockDetails object);
@info(name = 'MergeMaps')
INSERT INTO MergedStockStream
SELECT map:merge(stockMap) AS mergedStockDetails
FROM StockInputStream WINDOW TUMBLING_LENGTH(5);
In this example, a stream named StockInputStream is created to provide input to the MergeMaps query. This stream contains events with a map named stockMap. A sink stream MergedStockStream is created to collect the output.
The MergeMaps query processes events from StockInputStream in a tumbling window of size 5. For each batch of 5 events, the query applies the map:merge(stockMap) function to merge all stockMap instances into a single map. The merged map is then inserted into the MergedStockStream with the attribute name mergedStockDetails.