Putting Governor Limits To The Test

My Auntie Pat Tern is pretty accepting of cousin Tim Toady's behavior. "He's a teenager, after all, there's no better time for him to test his limits," she explained. So I decided to ask my developers to test their limits in Salesforce.

One Master object with 13 Detail objects, 
some of which are Masters in other relationships as well.

I wanted them to see for themselves how governor limits benefit the overall performance of the code they write. And I wanted them to experiment with ways to push those limits by trying to break things.

They built Processes, wrote triggers, and configured some unwieldy objects that I would never want to see in production all in an effort to push good performance to the very edge of being bad.

Some limits include object relationships.

A couple of these experiments proved that what they understood about limits was untrue. In one example, when it comes to Master-Detail relationships on custom objects, the documentation described a limit of 2^3. Firstly, 2^3 does not equal 8 here. Instead, it indicates that an object can have two M-D relationships and those can be three levels deep.

Take the example Parent <-- Child <-- GrandChild <-- GreatGrandChild where all relationships are Master <-- Detail. Some of the limits on this relationship structure are as follows:

• Parent cannot have a new Master (eg GrandParent) because of the limit on how deep the relationship levels can be. 
• GreatGrandChild does not show up as available to be a Master in other relationships because we are limited to three levels deep.
• Child cannot have a new Master because it already has two M <-- D relationships (even though only one of those points to a Master).
• Child can have new Details, that is, new GrandChild-level objects can be created as Details for Child even though Child already has two M <-- D relationships.
• Many Child-level objects can be created as Details for Parent (we stopped at over 50). 
• A Child-level object cannot be used as a junction object between records of a single Parent-level object. M <-- D relationships cannot be immediately self referencing like that.
• GrandChild-level and GreatGrandChild-level objects can have the same Master object as their Master, eg. GrandChild can point to Child and Parent as Masters even when Child already points to Parent as its Master. We daisy-chained six objects this way before hitting limits on the depth of the relationships.
• Child-level objects with two relationships pointing to Master objects cannot be Masters to new GrandChild-level objects. An object can have two Masters or it can have one Master and many Detail relationships or it can have no Master and many Detail relationships.

It was a fun exercise and demonstrated how limits benefit performance and how hard some of them can be to break. It gave the developers a chance to challenge their assumptions, be creative and gain a better understanding of the implications of limits when it comes to writing better code.

Secretly, Auntie Pattern believes that testing limits can help us appreciate why limits are important, but she wouldn't tell Tim Toady that.