We have a customer whom is experiencing this exception: External ID & Unique field limit exceeded. when they attempt to install our package.

I assume this is related to a conflict with another package that overrides that has added some extern ID & unique Ids to the same objects that we do.

The user can increase this limit from Salesforce. If they do, however, I need to figure out which object's our package adds a custom field too that is defined as a unique or external ids right?

However, our package doesn't add any external id & unique id fields to objects unless I'm misunderstand them: We have some look-up relationships to Leads and Contacts (is that considered part of the limit on External Id & Unique Ids)?

If so: is there anyway anyone can think of that would display which fields are contributing to toward this limit on an object by object basis?


In reading more about the customers limit, it strikes me that they are having an issue with an org wide external id limit of 10? Is the limit org wide?

2 Answers 2


It would be really weird to have lookups silently count as ext. id fields...

Try performing describe calls on all objects in your package that you suspect to clash? I have a custom field marked as "External Id", "Unique Case Insensitive" and I get this:

Schema.DescribeFieldResult f = Account.Account_Number__c.getDescribe();
System.debug(f.isExternalID());  // true
System.debug(f.isUnique());      // true
System.debug(f.isIdLookup());    // true

EDIT: There are 3 unique / ext. id fields per object. Ask support for increase.


How many formulas do you have on the objects that can be "common" with the other package. And do these formulas utilize in total 10 lookups to different places? (scroll to "Formulas: Number of Unique Relationships Per Object" text)?

I can imagine this being different kind of limit (put in place because too many lookups / formulas make joins in the underlying database extra painful to retrieve data). In that case you might have to consider rewriting some of your lookups into fields updated with triggers (always pain in managed package as I understand).

  • Agreed. I'm reading more about this users issue sand it strikes me that they're hitting an org wide externId limit - I thought it was an object by object limit. Commented Nov 15, 2012 at 23:01
  • 1
    It's not listed in the "limits" (fairly new addition for each object in the setup)... Officially we have up to 3/object and then we need a support ticket if I recall correctly. But I know some finance-related orgs are in ranges of 20+ per object ;)
    – eyescream
    Commented Nov 15, 2012 at 23:04
  • So this user is hitting an object limit? Since our package doesn't add any external id fields to any of the standard objects (and we don't have more than one on any of custom objects) why would they hit a limit when they install our package? Commented Nov 15, 2012 at 23:10
  • I've never heard about it being org wide, where have you dug out such info? success.salesforce.com/questionDetail?qId=a1X30000000HZqaEAG success.salesforce.com/questionDetail?qid=a1X30000000JEkpEAG ... Maybe the error msg is just a bit misleading, maybe installation of your stuff somehow causes recompilation of the other package? If you're positive you don't have any - I don't think you can do anything about it, client has to raise a support ticket.
    – eyescream
    Commented Nov 15, 2012 at 23:18
  • Yeah, it's not an org-wide limit. The error says a limit has been reached on the object itself (although I only count 1 field marked as 'Extern, Unique' that is packaged. I'll recommend the open a ticket with Salesforce Commented Nov 15, 2012 at 23:25

The max number of external id fields applies on a per object basis. It is a 'black tab' though, so if they cite a convincing enough reason to salesforce support, they should be able to have this limit bumped for them.

  • Still doesn't explain why they would be hitting it on a custom object when we're not hitting it in our development org - unless they're counting 'Roll Up Fields' Commented Nov 16, 2012 at 20:14

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