Skill: AL Performance Rules (BC SaaS)

Validation Gates

1. After Data Access: SetLoadFields before every FindSet/Find, IsEmpty() instead of Count() = 0
2. After Reports/APIs: DataAccessIntent = ReadOnly on read-only objects
3. Final: No += string concatenation in loops, TextBuilder used for 5+ concatenations

Note: BC23+ defaults to ReadCommitted isolation. Use UpdLock only for specific row locking.

Data Access Rules

// CORRECT: SetLoadFields
Item.SetLoadFields("No.", "Description", "Unit Price");
if Item.FindSet() then repeat /* ... */ until Item.Next() = 0;

// CORRECT: SetCurrentKey for indexed fields
CustLedgEntry.SetCurrentKey("Customer No.", "Posting Date");
CustLedgEntry.SetRange("Customer No.", Customer."No.");
CustLedgEntry.SetFilter("Posting Date", '>=%1', StartDate);

// CORRECT: IsEmpty instead of Count
if Customer.IsEmpty() then exit;

// CORRECT: CalcSums instead of loop
GLEntries.SetFilter("G/L Account No.", AccountFilter);
GLEntries.CalcSums(Amount);
TotalAmount := GLEntries.Amount;

// WRONG: Count() = 0 causes locks
if Customer.Count() = 0 then exit;  // AVOID!

// WRONG: Loop to sum values
repeat
    TotalAmount += GLEntries.Amount;  // AVOID!
until GLEntries.Next() = 0;

Warnings

SetLoadFields + Validate: Validate may touch other fields, triggering JIT loading and making the "fast" version slower.

// CAUTION: Validate may load additional fields
Customer.SetLoadFields("City");
Customer.FindSet();
repeat
    Customer.Validate(City, Customer.City.Trim());  // May trigger JIT loading!
until Customer.Next() = 0;

IsEmpty not always faster: If records exist in most cases, FindSet directly is faster (avoids double query).

// WRONG when records usually exist (e.g., Sales Lines for Sales Header)
if not SalesLine.IsEmpty() then  // Unnecessary query!
    SalesLine.FindSet();

// CORRECT: Just use FindSet when records expected
if SalesLine.FindSet() then
    repeat /* ... */ until SalesLine.Next() = 0;

Transaction Isolation

// Lock only last row for sequence
GLEntry.ReadIsolation := IsolationLevel::UpdLock;
GLEntry.FindLast();
exit(GLEntry."Entry No." + 1);

Pages & Reports

report 50100 "My Report"
{
    DataAccessIntent = ReadOnly;  // Uses read replica
}

// Page Background Task for heavy calculations
trigger OnAfterGetCurrRecord()
var
    TaskParameters: Dictionary of [Text, Text];
begin
    CurrPage.EnqueueBackgroundTask(TaskId, Codeunit::DoComplexCalculation, TaskParameters);
end;

Procedure Parameters

Pass only necessary fields, not entire records. Passing a record without var creates a memory copy.

// WRONG: Passes entire record (creates memory copy)
NoOfOrders := CountOrdersByCustomer(Customer);

local procedure CountOrdersByCustomer(Customer: Record Customer): Integer
begin
    SalesHeader.SetRange("Sell-to Customer No.", Customer."No.");
    exit(SalesHeader.Count());
end;

// CORRECT: Pass only needed field
NoOfOrders := CountOrdersByCustomer(Customer."No.");

local procedure CountOrdersByCustomer(CustomerNo: Code[20]): Integer
begin
    SalesHeader.SetRange("Sell-to Customer No.", CustomerNo);
    exit(SalesHeader.Count());
end;

// ALTERNATIVE: Use var to pass by reference (no copy)
local procedure ProcessCustomer(var Customer: Record Customer)

Async Patterns

Strings & Collections

// CORRECT: TextBuilder for loops
var StringBuilder: TextBuilder;
begin
    foreach Item in Items do
        StringBuilder.AppendLine(Item.Description);
    exit(StringBuilder.ToText());
end;

// WRONG: += in loop - AVOID!
foreach Item in Items do
    Result += Item.Description + '\';

Rule: Use TextBuilder for 5+ concatenations or any loop. Use Dictionary/List instead of temporary tables for in-memory operations.

Code Review Checklist

- [ ] SetLoadFields before FindSet/Find on tables with extensions?
- [ ] SetCurrentKey when filtering on non-primary key fields?
- [ ] IsEmpty() instead of Count() = 0? (only when records rarely exist)
- [ ] CalcSums instead of loop for summing?
- [ ] DataAccessIntent = ReadOnly on read-only reports/APIs?
- [ ] TextBuilder for string concatenations in loops?
- [ ] Procedure parameters: fields instead of full records?
- [ ] CommitBehavior on critical integration events?

External Documentation

• Microsoft: Performance Developer Guide
• Stefan Šošić: Performance Patterns Part 1
• Stefan Šošić: Performance Patterns Part 2