getReference(): That Shortcut You Regret Later

Goran WitchDoc · 3 weeks ago

We’ve all been there. You need a quick lookup, so you reach for getReference(). It works… until the form slows down and the complaints start piling up.

I still remember the day I leaned a little too hard on getReference(). It was a new onboarding workflow, and the requirement sounded simple: populate a few fields when the hiring manager is selected. Easy, right?

So, I sprinkled in a couple of g_form.getReference() calls—five of them, to be exact. Lookups on manager, department, cost center, location, and role. By the time I was done, the form looked fine in testing. But once it hit production, the complaints started rolling in:

“Why does this form take forever to load?”

Yeah… turns out five getReference() calls in a row is less “clever shortcut” and more “death by a thousand GlideRecord queries.” Lesson learned.

Why This Happens

g_form.getReference() feels like the duct tape of ServiceNow client development. Quick fix, sticks to anything, solves the problem, until it doesn’t.

How it works: It fetches the entire referenced record asynchronously and passes it to your callback.
The problem: It doesn’t care that you only needed the location field, you’re pulling in every column of the user record. Multiply that by a few calls, and suddenly your form is making round trips that add noticeable lag.

A simple example:

g_form.getReference('caller_id', function(caller) {
  g_form.setValue('u_location', caller.location + '');
});

Perfectly fine in a small lookup. Dangerous at scale.

GlideAjax to the Rescue

Now, GlideAjax isn’t as instant-gratification as getReference(). You need a Script Include, you need to define what comes back, and you need to think a little harder. But here’s the kicker: you control the payload.

Client script:

var ga = new GlideAjax('GetCallerInfo');
ga.addParam('sysparm_name','getBasics');
ga.addParam('sysparm_user', g_form.getValue('caller_id'));
ga.getXMLAnswer(function(ans){
  var data = JSON.parse(ans);
  g_form.setValue('u_location', data.location, data.locationDisplay);
});

Script Include:

var GetCallerInfo = Class.create();
GetCallerInfo.prototype = Object.extendsObject(global.AbstractAjaxProcessor, {
  getBasics: function() {
    var id = this.getParameter('sysparm_user');
    var gr = new GlideRecordSecure('sys_user'); // ACLs enforced
    if (!gr.get(id)) return JSON.stringify({ error: 'not_found' });
    return JSON.stringify({ location: gr.getValue('location'), locationDisplay: gr.getDisplayValue('location') });
  },
  isPublic: function() { return true; }
});

Now you’re fetching exactly what you need, honoring ACLs, and keeping the form snappy.

Rule of Thumb (From the School of Hard Knocks)

One field, one time, small table? getReference() is fine.
Multiple lookups, big tables, or production-grade flows? GlideAjax is the grown-up choice.
Values always needed on load? Preload them with g_scratchpad in a Display Business Rule—faster, cleaner, safer.

My Takeaway

getReference() is like grabbing fast food, great when you’re in a hurry, but you can’t build a diet on it. GlideAjax is the proper kitchen setup: takes a little prep, but it scales when you’ve got to feed a crowd.

Your Turn

Have you ever regretted leaning on getReference() after a form slowed to a crawl? What tipped you toward switching to GlideAjax?

//Göran
Author:
Witch Doctor's Playbook: ServiceNow AI
The Witch Doctor's Guide To ServiceNow