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List Functions

List functions allow you to create and interact with lists.

For information on performing scatter and gather using list:tokenize(), and list:collect(), refer to the examples in Data Pipeline Examples.

Input​

Below event is sent to ProductComboStream,

['Ice Cream', 'Chocolate', 'Cake']

Output​

After processing, the following events will be arriving at each stream:

  • NewListStream: [[Ice Cream, Chocolate, Cake]]
  • ListAnalysisStream: [true, true, false, Chocolate, 3]
  • UpdatedListStream: [[Ice Cream, Chocolate, Toffee]]

Example​

This example shows how to use basic list functions.

-- Defines `ProductComboStream` having `string` type attributes `product1`, `product2`, and `product3`.
CREATE STREAM ProductComboStream ( product1 string, product2 string, product3 string);


@info(name = 'Create-list')
-- Create a list with values of `product1`, `product2`, and `product3`.
insert into NewListStream
select list:create(product1, product2, product3)
            as productList
from ProductComboStream;


@info(name = 'Check-list')
-- Check if `productList` is a List.
insert into ListAnalysisStream
select list:isList(productList) as isList,
-- Check if `productList` contains `'Cake'`.
       list:contains(productList, 'Cake')
            as isCakePresent,
-- Check if `productList` is empty.
       list:isEmpty(productList) as isEmpty,
-- Get the value at index `1` from `productList` .
       list:get(productList, 1) as valueAt1,
-- Get size of `productList`.
       list:size(productList) as size
from NewListStream;


@info(name = 'Clone-and-update')
-- Clone `productList`, add `Toffee` to the end of the list, and remove `Cake` from the list.
insert into UpdatedListStream
select list:remove(
            list:add(list:clone(productList), "Toffee"),
            "Cake") as productList
from NewListStream;