Learning ServiceNow

Avoiding Nested Loops

Nested loops have their place in development, but if you aren't careful, they can lead to serious performance degradation due to the fact that the inner loop will run a certain number of times, multiplied by the number of times the outer loop runs.

It is often possible to avoid having to run a nested loop, in favor of running two separate loops (which means that each loop would only run a set number of times).

Consider the following code:

var innerGR; var results = [];  var outerGR = new GlideRecord('table_name'); outerGR.query(); while (outerGR.next()) {     innerGR = new GlideRecord('other_table_name');     innerGR.addQuery('field', outerGR.getValue('something_to_compare'));     innerGR.query();     while (innerGR.next()) {