Count records matching a condition with GlideAggregate

Most developers instinctively reach for GlideRecord iteration to count matching records, but this forces ServiceNow to load every row into memory just to increment a counter. GlideAggregate with COUNT pushes the counting down to the database layer, returning only the final number. The performance difference is dramatic — I've seen 30-second Business Rules drop to under 2 seconds by switching from GlideRecord loops to aggregate counts. The critical mistake is using getValue() instead of getAggregate() to retrieve the count — that'll return null and waste your time debugging.

When to use this

• Dashboard widgets showing counts of incidents by state, priority, or assignment group
• Business Rules that validate counts before allowing state transitions (e.g., "can't close parent with open child tasks")
• Scheduled Jobs calculating SLA compliance metrics or workload distribution reports
• Script Includes that need fast counts for conditional logic without processing individual records

When NOT to use this

• Client scripts — use GlideAjax to call a Script Include with GlideAggregate instead
• When you also need field values from the matching records — use GlideRecord iteration to count and process in one pass
• Complex queries with OR conditions across multiple fields — GlideAggregate doesn't support addOrCondition()
• Counting records across multiple tables — aggregate each table separately then sum the results

Key behaviors and gotchas

• getAggregate('COUNT') returns a string, not a number — always wrap with parseInt() for math operations
• Empty result sets return no rows from ga.next() — always handle the false case to avoid returning undefined
• groupBy() with COUNT requires a while loop, not single next() call — one row per group
• State field queries use integers ('1,2,3'), not choice labels — GlideAggregate bypasses display value conversion
• ACLs still apply — counts reflect only records the current user can read, not total table records
• Reference field queries (assignment_group) return sys_ids in getValue(), not display names