skill-performance

Skill: AL Performance Optimization

Purpose

Identify, analyze, and fix performance bottlenecks in AL code: inefficient queries, FlowField issues, loop anti-patterns, and data-volume problems in Business Central.

When to Load

This skill should be loaded when:

• A page, report, or batch process is slow or timing out
• CPU profiling is needed to identify hotspots
• A static triage of the codebase is requested for performance issues
• A feature involves large-dataset processing or high-frequency code paths
• AL0896 (circular FlowField) errors appear
• Architecture review requires performance analysis of a new design

Core Patterns

Pattern 1: SetLoadFields + Early Filtering

Always filter before finding, and load only needed fields. Order matters.

// ✅ Correct: SetRange first, SetLoadFields before Find
Item.SetRange("Third Party Item Exists", false);
Item.SetLoadFields("Item Category Code", Description);
if Item.FindSet() then
    repeat
        // Only "Item Category Code" and Description loaded from DB
    until Item.Next() = 0;

// ❌ Wrong: SetLoadFields after SetRange (ignored), loads all fields
Item.SetLoadFields("Item Category Code");
Item.SetRange("Third Party Item Exists", false);
Item.FindFirst();

// ❌ Wrong: No filter — full table scan
procedure GetCustomersByCity(CityFilter: Text): Integer
var
    Customer: Record Customer;
    Count: Integer;
begin
    if Customer.FindSet() then       // loads entire Customer table
        repeat
            if Customer.City = CityFilter then
                Count += 1;
        until Customer.Next() = 0;
end;

// ✅ Correct: Filter pushed to DB
procedure GetCustomersByCity(CityFilter: Text): Integer
var
    Customer: Record Customer;
begin
    Customer.SetRange(City, CityFilter);
    Customer.SetRange(Blocked, Customer.Blocked::" ");
    exit(Customer.Count());
end;

Pattern 2: Set-Based Aggregation (CalcSums / CalcFields)

Avoid manual loops for aggregation — push the sum to the database.

// ❌ Loop accumulation — N rows fetched and processed in AL
procedure GetTotalSales(CustomerNo: Code[20]): Decimal
var
    Entry: Record "Cust. Ledger Entry";
    Total: Decimal;
begin
    Entry.SetRange("Customer No.", CustomerNo);
    if Entry.FindSet() then
        repeat
            Total += Entry.Amount;
        until Entry.Next() = 0;
    exit(Total);
end;

// ✅ CalcSums — single aggregation query at DB level
procedure GetTotalSales(CustomerNo: Code[20]): Decimal
var
    Entry: Record "Cust. Ledger Entry";
begin
    Entry.SetRange("Customer No.", CustomerNo);
    Entry.CalcSums(Amount);
    exit(Entry.Amount);
end;