Executing SOQL with User Mode and then DML with user Mode causing Exception

Question

I couldn't find if SOQL and DML become interlinked when using WITH USER_MODE with SOQL and DML both in single transaction.

I've below sample code to be triggered on a button from an LWC:

@AuraEnabled
public static void ruleMoveOrder(String ruleId) {
    My_Rule_Obj__c rule     = [SELECT Id, Order__c, My_Rule__c FROM My_Rule_Obj__c WHERE Id = :ruleId WITH USER_MODE];
    rule.Order__c           = rule.Order__c + 1;
    Database.update(rule, AccessLevel.USER_MODE);
}

This code is causing an exception like this on DML statement line Database.update(rule, AccessLevel.USER_MODE):

"System.DmlException: Operation failed due to fields being inaccessible on Sobject My_Rule_Obj__c, check errors on Exception or Result!"

The Debug Logs generated shows this information:

03:53:30.5 (21945797)|SOQL_EXECUTE_BEGIN|[76]|Aggregations:0|SELECT Id, Order__c, My_Rule__c FROM My_Rule_Obj__c WHERE Id = :tmpVar1 WITH USER_MODE
03:53:30.5 (43468810)|SOQL_EXECUTE_END|[76]|Rows:1
03:53:30.5 (43721320)|VARIABLE_SCOPE_BEGIN|[76]|rule|My_Rule_Obj__c|true|false
03:53:30.5 (43776306)|VARIABLE_ASSIGNMENT|[76]|rule|{"Id":"a1C5g000005kyuUEAQ","Order__c":1,"My_Rule__c":"a115g0000009qd2AAA"}|0xee3a1fd
03:53:30.5 (43785988)|STATEMENT_EXECUTE|[78]
03:53:30.5 (44245154)|VARIABLE_ASSIGNMENT|[78]|this.Order__c|2|0xee3a1fd
03:53:30.5 (44256849)|STATEMENT_EXECUTE|[79]
03:53:30.5 (44346702)|VARIABLE_SCOPE_BEGIN|[6]|System.AccessLevel.SYSTEM_MODE|System.AccessLevel|true|true
03:53:30.5 (44367947)|VARIABLE_SCOPE_BEGIN|[4]|System.AccessLevel.USER_MODE|System.AccessLevel|true|true
03:53:30.5 (44432606)|SYSTEM_METHOD_ENTRY|[1]|AccessLevel.AccessLevel()
03:53:30.5 (44443041)|STATEMENT_EXECUTE|[1]
03:53:30.5 (47023769)|SYSTEM_METHOD_EXIT|[1]|AccessLevel
03:53:30.5 (47219802)|DML_BEGIN|[79]|Op:Update|Type:My_Rule_Obj__c|Rows:1
03:53:30.5 (47308428)|HEAP_ALLOCATE|[EXTERNAL]|Bytes:8
03:53:30.5 (48128599)|DML_END|[79]
03:53:30.5 (49360391)|FATAL_ERROR|System.DmlException: Operation failed due to fields being inaccessible on Sobject My_Rule_Obj__c, check errors on Exception or Result!

The error would go away and able to update correctly, as it should with below code:

@AuraEnabled
public static void ruleMoveOrder(String ruleId) {
    My_Rule_Obj__c rule     = [SELECT Id, Order__c, My_Rule__c FROM My_Rule_Obj__c WHERE Id = :ruleId WITH USER_MODE];
    My_Rule_Obj__c rule2    = new My_Rule_Obj__c(Id = rule.Id);
    rule2.Order__c          = rule.Order__c + 1;
    Database.update(rule2, AccessLevel.USER_MODE);
}

Why would this be? Does SOQL query using USER_MODE makes the rule variable instance sort of readonly? Can we not directly update the variable with this security system in place?

NOTE:

• Org wide sharing rule do not matter - object sharing settings are public read/write.
• Field level and Object permissions properly enabled with full CRUD and FLS permissions to edit and Read.

Answer 1

My_Rule__c appears to be a master-detail relationship field with reparenting disabled. For some reason, supplying the same value as what is already in the field still causes this error, because the field cannot be specified in this configuration. When you used new My_Rule_Obj__c(Id = rule.Id), you didn't include the My_Rule__c field, which is why you didn't get the error message.

You can validate this hypotheses with a simple execute anonymous script:

Assert.isTrue(My_Rule_Obj__c.My_Rule__c.getDescribe().isUpdateable());

Which should fail if the field is indeed a master-detail relationship with reparenting disabled.

The moral of the story is: don't include fields you don't intend to update in your query.

Answer 2

I believe this is a bug with AccessLevels. Until it's fixed, you can use the following workaround:

List<My_Rule_Obj__c> rules = new List<My_Rule_Obj__c>{ rule };
List<My_Rule_Obj__c> strippedRules = Security.stripInaccessible(AccessType. UPDATABLE, rules).getRecords();
Database.insert(strippedRules, AccessLevel.USER_MODE);

More info: https://salesforce.stackexchange.com/a/412743/61394