Through some customizations, we have modified the Account object to either have a recordtype of Company or Branch. In the event that an Account has a recordtype of Branch, we populate a custom field named Home_Office__c with the Company's ID (Account ID). As part of a larger contact validation trigger, I am trying to grab the IDs of all the Branches whose Home_Office__c falls within a certain Set. 

Here's the excerpt of my trigger where I create a Set of Home_Office__c from the Triggers Account:

Set<ID> homeID = new Set<ID>();
				
for (Account a : [SELECT Home_Office__c FROM Account WHERE Id =: accID AND Home_Office__c != null]) {
					
homeID.add(a.Home_Office__c);
					
}

Here's the excerpt where I create a Set of Account IDs that fall within the Home_Office__c set:

Set<ID> branchID = new Set<ID>();
				
for (Account a : [SELECT Id FROM Account WHERE Home_Office__c IN : homeID]) {
					
branchID.add(a.Id);

}

FYI - I split these values over two sets becausing I'm mapping contact names first from the parent company and then from all the branches. 

The first set will rarely ever be larger than 1 row, with the branch set reaching a size of around 600. However, it is the branch set that is causing the System.Exception: Too many query rows: 1001.

I thought I had thoroughly tested this in our Sandbox, but only when I deployed the trigger to production did I run across this error. I have since updated our Sandbox to reflect records similar to production, and through testing, the only conclusion I can come to is that the second query is grabbing all Account IDs; not just ones with a valid Home_Office__c value.

Any idea of why this may be happening? I've avoided including the entire trigger since it all had worked fine before, but if necessary I'll post it. Thanks in advance.

Adriel