MIXED_DML_OPERATION error in Salesforce Apex Trigger when updating User objects

Question

I have a trigger on a Contact object and when I try to update a User record in this trigger I get the following exception:

"MIXED_DML_OPERATION, DML operation on setup object is not permitted after you have updated a non-setup object (or vice versa): User, original object: Contact"

Trigger code:

trigger UpdateContactTrigger on Contact (after update) {

    User u = [SELECT Id, IsActive FROM User WHERE IsActive = true];

    u.IsActive = false;
    update u;

}

How can I avoid this error while updating User record's fields from a Contact trigger?

Vladimir 'lenin_ra' Halme · Accepted Answer · 2012-04-13 15:03:20Z

Salesforce categorizes objects into so called setup and non-setup objects. User is a setup object while Contact is a non-setup object. Salesforce restricts DML operations so that both kinds of objects can't be manipulated in the same context.

There's a workaround for this problem placing DML code for conflicting object to a @future method as described in the end of this document and the previous answer.

In my case using @future method didn't work because there was an update trigger on User that called another @future method and Salesforce doesn't allow calling a @future method from another @future method.

So I came up with another workaround that works for some cases for User objects.

From API version 15.0 Salesforce actually allows updates on custom fields of a User object in the same context with non-setup object updates. So if you need to update User's standard field, you can use a custom proxy field with a 'before update' trigger on the User object.

If you need to change User's IsActive field, add a custom IsActiveProxy field to the user and perform your update in a trigger on it:

trigger UpdateContactTrigger on Contact (after update) {

    User u = [SELECT Id, IsActive FROM User WHERE IsActive = true];

    u.IsActiveProxy__c = false;
    update u;

}

Then create a 'before update' trigger on a User that copies the proxy field value to the standard field:

trigger BeforeUpdateUserTrigger on User (before update) {

    for(User user : trigger.new) {

        if(user.IsActive != user.IsActiveProxy__c) {
            user.IsActive = user.IsActiveProxy__c;
        }

    }

}

That's it! It worked for me.

Łukasz Skrodzki · Accepted Answer · 2012-04-13 07:49:42Z

2

You should define @future method which will do the update and call this method from trigger.

@future
updateUser(){
    User u = [SELECT Id, IsActive FROM User WHERE IsActive = true];

    u.IsActive = false;
    update u;
}

and call it in trigger:

trigger UpdateContactTrigger on Contact (after update) {
    updateUser();
}

answered Apr 13, 2012 at 7:49

Łukasz Skrodzki

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1 Comment

Vladimir 'lenin_ra' Halme Over a year ago

Yes I have tried this approach but it doesn't work for me because there's a trigger on the User that calls a '@future' method and calling '@future' method from another '@future' method is not allowed in Salesforce. I have found an alternative workaround that solves the problem and I will post it as an answer later. Thanks for reply!

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