Data Loader behavior with addError()

Question

I have a before update trigger on User object which checks for certain User fields. If that field matches a condition I am supposed to skip the update of that user record, else make some field updates on that record. I achieved this using addError() method.

newUser.addError('Skipping non-company employees');

When I use data loader to update multiple records, the before update trigger is executing multiple times. For example, if I have 4 records in my CSV file with one record to be skipped and 3 different email updates to be made on other 3 records, the individuals with the updated email IDs are getting 3 emails each for verifying the email ID change. This means my before update trigger is fired multiple times. When I do not have any records to be skipped with addError(), this the users get only one verification email, as expected.

This is very strange. I have referred this post, but the explanation given should not make field updates multiple times as per my knowledge.

Any help would be appreciated!

Answer 1

You can consider not using addError at all. Just bypass the users you don't need to run your code on: since you are running a trigger on before update you can easily copy the changed fields form the existing record on the database, which are available on Trigger.old and Trigger.oldMap as both list and map of Id to User.

Answer 2

If you make updates to a batch of records through the API or using apex with allOrNone set to false, and a trigger uses addError on some of the records within a batch, Salesforce will rollback the changes that occurred within the trigger, and then call the trigger again with the records that did not have errors.

Note that if the same trigger operates in both a before and after context, and addError is used in the before context, the trigger will be called with the after context on the non-error records before rolling back, and then calling trigger again (in both the before and after contexts).