How to filter out tuple sub-field elements by predicate

Issue

I have a list of tuples, where the schema for the tuple element has a field named 'status'. I would like to filter out any elements where status is 'inactive'. How can I accomplish this in Event Flow?

Solution

In StreamBase 7.4 or later, use the filterlist() function, as defined in the Help under

• StreamBase Home > StreamBase References > StreamBase Expression Language Functions > (sub-heading) Simple Functions: Lists

For example, if the tuple list element has a Named Schema 'Customer' with sub-fields 'name' and 'status', you can filter out inactive entries in a Map operator using the following expression:

 filterlist(input1.Customer, function notInactive(cust Customer) {cust.status != 'inactive'})

This expression creates a user-defined function, 'notInactive', which applies the predicate cust.status != 'inactive'.