Split a List into smaller lists before publishing platform events

Question

I wanted to split a map value which has a size of 2000 into small lists of max size 600 each and publish this smaller lists using platform events. I'm performing an update using platform event triggers. What's the best way of doing it ? Below is my code

if(WrapObjMap.keyset().size() > maxSizePerReq) {
                system.debug('Inside If');
                for(Integer i = 0 ; i < (WrapObjMap.keyset().size() / 600)+1 ; i++){
                    SplitList = new List<platform_Event__e>();
                    SplitFinalList = new List<platform_Event__e>();
                    for(Integer j=(i*600); (j<(i*600)+600) && j<WrapObjMap.keyset().size() ; j++){
                        SplitList.add(new platform_Event__e(long_text_area_field__c =  JSON.serialize(WrapObjMap.values().get(j))));


                    }

                    List<Database.SaveResult> results = EventBus.publish(SplitList);

                }
            }

Answer 1

As per your comments, I'm afraid that your use of Platform Events is an anti-pattern as you're not using them to integrate directly with your external system. In other words, you're using them to communicate from Salesforce (Apex endpoint) to Salesforce (Apex trigger).

What you need for your use case is either Batchable, Queueable or Schedulable Apex. Check out the documentation for more information on these options: https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_async_overview.htm

Answer 2

if I didn't misunderstood your requirements then please try to use the below code or else correct me

if(optyIdTWrapObjMap.keyset().size() > maxSizePerReq) {
    for(Integer i = 0 ; i < optyIdTWrapObjMap.keyset(); i++){
        if (i < 600) {
            fillTheFirstList.add(listElement);
        } else if(i < 1200){
            fillThe2ndList.add(listElement);
        } else if(i < 1800){
            fillThe3rdList.add(listElement);
        }
    }
}

Answer 3

Since Apex doesn't allow run time new list creation we can use a map to do the trick for us :)

Map<Integer,List<Opportunity_Assignment__e>> opportunityEventMap = new Map<Integer,List<Opportunity_Assignment__e>> ();

if(optyIdTWrapObjMap != null) {

    Integer keyValue = 0;

    //Creating Map
    for(Integer keyInteger: optyIdTWrapObjMap.keyset()) {

        if(opportunityEventMap.containsKey(keyValue) && opportunityEventMap.get(keyValue).size() <= 600)
        opportunityEventMap.get(keyValue).add(Opportunity_Assignment__e(AIR_Opportunties__c =  JSON.serialize(optyIdTWrapObjMap.values().get(keyInteger))));

        else{
            keyValue++;
            opportunityEventMap.put(keyValue,new Opportunity_Assignment__e(AIR_Opportunties__c =  JSON.serialize(optyIdTWrapObjMap.values().get(keyInteger))));
        }
    }
}

//Publish the events to bus
if(opportunityEventMap != null && !opportunityEventMap.keyset().isEmpty()) {
    for(Integer eventKey : opportunityEventMap.keyset()) {

        if(opportunityEventMap.containsKey(eventKey) && !opportunityEventMap.get(eventKey).isEmpty())
        EventBus.publish(opportunityEventMap.get(eventKey));
    }
}

Hope this helps!!

Answer 4

This is a simple pattern to use ... I used Object as a placeholder to avoid dealing with your variable names

Integer MAXCHUNK = 600;
SObject[] chunkRecs = new List<SObject();
for (Object obj : myMap.values()) {
   chunkrecs.add(new MyPE__e (fld = ..., ..));
   if (chunkRecs.size() == MAXCHUNK) {
     EventBus.publish(chunkRecs);
     chunkRecs.clear();
   }
}
if (!chunkRecs.isEmpty()) { // a partial chunk
  EventBus.publish(chunkRecs);
}