Throw error message and capture it in error log custom object

Question

there is a requirment where when data is upserted in bulk from external system, we need to check for certain criteria, if it does not match, we should prevent the insert/update and log the error in custom object.

However using before trigger to prevent the upsertion does not allow error log insertion into the custom object as everything gets rolled back.Is there any other approach for the same.

We tried allowing the DML and then delete the unmatched record. HOwever in case of update we will never know which fields were updated to revert back. Any suggestions

Thanks

Answer 1

You can now do this by way of Platform Events. Unlike normal DML operations, Platform Events are not rolled back in a transaction, even if there are failures. To use this feature, there's a few steps involved.

First, create your Log object, if you haven't already. Next, create a Platform Event that has a field (or more, if you desire). After that, add a trigger to actually create the logs. Here's an example:

// Note: __e is not a typo. It is the special extension used by Platform Events.
trigger LogErrorEventTrigger on LogErrorEvent__e (after insert) {
    Log__c[] logs = new Log__c[0];
    for(LogErrorEvent__e record: Trigger.new) {
        logs.add(new Log__c(Log__c=record.Log__c));
    }
    insert logs;
}

To actually use this, you need to "publish" these events:

trigger CustomObjectTrigger on CustomObject__c (after insert) {
    LogErrorEvent__e[] logs = new LogErrorEvent__e[0];
    for(CustomObject__c record: Trigger.new) {
        logs.add(new LogErrorEvent__e(Log__c='Blocked insert'));
        record.addError('Block insert');
    }
    EventBus.publish(logs);
}

This will prevent inserts, updates, deletes, undeletes, whichever you would like to handle, and log the appropriate message into your log queue.