Bulkify Apex Trigger when Launching Flow

Question

I am trying to figure out how to properly "bulkify" a trigger to handle mass deletes when launching an autolaunched flow. Documentation seems to be sparse on this. Will the flow bulkify itself if I instantiate it for every object in the collection, or do I need to use a set and loop through that before launching a flow (thinking this because the mass delete could include multiple of the same FundID parameter I am passing into the flow)?

Yes - I will move this to a trigger handler once I get some feedback on this.

Code below:

if(trigger.isDelete) 
{
    if(trigger.isAfter)
    {
         for (Manager_Contact_Relationship__c mcr : Trigger.Old){

             Map<String, Object> params = new Map<String, Object>();
             params.put('FundID', mcr.Manager_Fund__c);

             Flow.Interview.Update_MCR_Records MCRFlow = new Flow.Interview.Update_MCR_Records(params);

             MCRFlow.start();
         }
    }
}

Answer 1

The system never optimizes triggers or flows of its own accord. You will need need to gather all the relevant ID values and then call the flow. However, you should be wary of using flows in bulk anyways, because they tend to consume a lot more CPU time than simply writing Apex Code. When you call a flow, it runs synchronously, as if you'd just called another method. They are not all gathered together and run asynchronously.

Answer 2

You DO NOT want to be calling a flow 200 times from within a for loop in a trigger in the case that 200 Manager_Contact_Relationship__c records are deleted at once. Assuming your flow does any data retrieval (essentially SOQL queries) or saves any data to the database (DML statements), you have committed a cardinal sin against Apex best practices by putting it inside a for loop in a trigger.

As much as I'm skeptical about calling a flow from a trigger at all, due to the fact that it's hard to test and that a change to the flow can break the trigger and prevent these records for being deleted, I'd question the necessity for it at all.

But if you are going to do it, you should build your flow to accept a collection of IDs, and bulkify the flow the way you would a trigger - assume that you can get a collection of 200 IDs and make sure it can handle at least that many records without hitting any governor limits. I would suggest writing unit tests that test the result of the trigger + flow, so that you could have some kind of quality control on it.

Answer 3

Winter '23 enables Apex to launch a collection of flows. The flow logic is bulkified automatically. Your Update_MCR_Records flow can be designed from the perspective of a single request.

Here are the docs for the Invocable.Action classes and methods: developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_class_Invocable_Action

This updated trigger performs the bulk invoke (ie 200 invokes will use only 1 DML, below)

if(trigger.isDelete) 
{
    if(trigger.isAfter)
    {
        Invocable.Action impl; // prepare the action using name of flow
        impl = Invocable.Action.createCustomAction('flow','Update_MCR_Records')

        // snip the 0th interview
        // (loop is used instead)
        action.clearInvocations();
        
        for (Manager_Contact_Relationship__c mcr : Trigger.Old
        {
            impl.addInvocation(); // build interview for each record
            impl.setInvocationParameter('FundID', mcr.Manager_Fund__c);
        }

        // run bulk
        impl.invoke();
    }
}

It uses Flow's bulk engine and doesn't need any workaround with collection variables. Eg:

Answer 4

OK what about this:

When a delete happens on your child, do an update to the parent, via a afterdelete() event. Let's set the textString you're populating to be 'recalculate'

Then create a processbuilder to look at the textString where when 'recalculate' to call your flow to look at all the child records and repopulate the text string?

Would that work?