# Temporary Table Safety - AL Code Examples

## Good Examples

### Secure Temporary Table with Cleanup
```al
procedure ProcessSensitiveCustomerData(CustomerFilter: Text): Boolean
var
    Customer: Record Customer;
    TempCustomerBuffer: Record Customer temporary;
    ProcessingResult: Boolean;
begin
    // Validate user permissions before populating temporary table
    if not UserPermissions.CanViewCustomerData() then
        exit(false);

    Customer.SetFilter("No.", CustomerFilter);
    if not Customer.FindSet() then
        exit(false);

    try
        // Populate temporary table with filtered data
        repeat
            // Only include data user has permission to see
            if UserPermissions.CanViewCustomer(Customer."No.") then begin
                TempCustomerBuffer := Customer;
                TempCustomerBuffer.Insert();
            end;
        until Customer.Next() = 0;

        // Process temporary data
        ProcessingResult := ProcessCustomerBuffer(TempCustomerBuffer);

    finally
        // Always clear sensitive temporary data
        TempCustomerBuffer.DeleteAll();
    end;

    exit(ProcessingResult);
end;
```

### Permission-Aware Temporary Processing
```al
procedure GenerateCustomerReport(CustomerNo: Code[20]): Text
var
    Customer: Record Customer;
    CustLedgerEntry: Record "Cust. Ledger Entry";
    TempReportBuffer: Record "Name/Value Buffer" temporary;
    ReportText: Text;
begin
    // Early permission validation
    if not Customer.ReadPermission then
        exit('Access Denied');

    if not Customer.Get(CustomerNo) then
        exit('Customer Not Found');

    // Verify specific customer access
    if not UserPermissions.CanViewCustomer(CustomerNo) then
        exit('Access Denied');

    try
        // Build temporary report data with permission checks
        TempReportBuffer.Init();
        TempReportBuffer.Name := 'Customer Name';
        TempReportBuffer.Value := Customer.Name;
        TempReportBuffer.Insert();

        // Only include financial data if user has permission
        if CustLedgerEntry.ReadPermission and UserPermissions.CanViewFinancialData() then begin
            CustLedgerEntry.SetRange("Customer No.", CustomerNo);
            CustLedgerEntry.CalcSums("Remaining Amt. (LCY)");

            TempReportBuffer.Init();
            TempReportBuffer.Name := 'Outstanding Amount';
            TempReportBuffer.Value := Format(CustLedgerEntry."Remaining Amt. (LCY)");
            TempReportBuffer.Insert();
        end;

        // Generate report from temporary data
        ReportText := BuildReportFromBuffer(TempReportBuffer);

    finally
        // Always clear temporary data containing sensitive information
        TempReportBuffer.DeleteAll();
    end;

    exit(ReportText);
end;
```

### Scoped Temporary Table Processing
```al
procedure CalculateItemProfitability(ItemFilter: Text): Decimal
var
    Item: Record Item;
    ItemLedgerEntry: Record "Item Ledger Entry";
    TempProfitBuffer: Record "Integer" temporary;
    TotalProfit: Decimal;
    LineNo: Integer;
begin
    // Validate permissions for cost data access
    if not UserPermissions.CanViewCostInformation() then
        exit(0);

    Item.SetFilter("No.", ItemFilter);
    if not Item.FindSet() then
        exit(0);

    try
        LineNo := 0;
        repeat
            // Only process items user can view
            if UserPermissions.CanViewItem(Item."No.") then begin
                LineNo += 10000;

                // Calculate profit for this item
                ItemLedgerEntry.SetRange("Item No.", Item."No.");
                ItemLedgerEntry.CalcSums("Sales Amount (Actual)", "Cost Amount (Actual)");

                // Store in temporary buffer with limited scope
                TempProfitBuffer.Init();
                TempProfitBuffer.Number := LineNo;
                TempProfitBuffer.Insert();

                TotalProfit += (ItemLedgerEntry."Sales Amount (Actual)" - ItemLedgerEntry."Cost Amount (Actual)");
            end;
        until Item.Next() = 0;

    finally
        // Cleanup temporary data
        TempProfitBuffer.DeleteAll();
    end;

    exit(TotalProfit);
end;
```

## Bad Examples

### Temporary Table Without Permission Validation
```al
procedure ProcessAllCustomerData(): Boolean
var
    Customer: Record Customer;
    TempCustomerBuffer: Record Customer temporary;
begin
    // BAD: No permission validation before accessing sensitive data
    Customer.FindSet();
    repeat
        TempCustomerBuffer := Customer;
        TempCustomerBuffer.Insert();
    until Customer.Next() = 0;

    // BAD: Processing all customer data regardless of user permissions
    ProcessCustomerBuffer(TempCustomerBuffer);

    // BAD: No cleanup of sensitive temporary data
    exit(true);
end;
```

### No Cleanup in Error Scenarios
```al
procedure RiskyTemporaryProcessing(CustomerNo: Code[20]): Boolean
var
    Customer: Record Customer;
    TempSensitiveData: Record Customer temporary;
begin
    if Customer.Get(CustomerNo) then begin
        TempSensitiveData := Customer;
        TempSensitiveData.Insert();

        // BAD: If this processing fails, temporary data is not cleaned up
        if ProcessSensitiveData(TempSensitiveData) then begin
            TempSensitiveData.DeleteAll();
            exit(true);
        end;

        // BAD: Error path doesn't clean up temporary data
        exit(false);
    end;
end;
```

### Cross-Session Data Leakage Risk
```al
codeunit 50100 "Unsafe Temporary Processing"
{
    // BAD: Global temporary table could leak data between sessions
    var
        GlobalTempBuffer: Record Customer temporary;

    procedure ProcessCustomer(CustomerNo: Code[20]): Boolean
    begin
        // BAD: Global temporary data persists across procedure calls
        GlobalTempBuffer."No." := CustomerNo;
        GlobalTempBuffer.Insert();

        // BAD: No session isolation or cleanup
        exit(ProcessGlobalBuffer());
    end;
}
```

## Best Practices

### Comprehensive Error Handling
```al
procedure SecureTemporaryProcessing(RecordID: RecordID): Boolean
var
    RecordRef: RecordRef;
    TempProcessingBuffer: Record "Integer" temporary;
    ProcessingSuccess: Boolean;
    ErrorOccurred: Boolean;
begin
    // Early permission validation
    if not UserPermissions.CanAccessRecord(RecordID) then
        exit(false);

    if not RecordRef.Get(RecordID) then
        exit(false);

    try
        // Initialize temporary processing with minimal data
        TempProcessingBuffer.Init();
        TempProcessingBuffer.Number := RecordID.RecordId;
        TempProcessingBuffer.Insert();

        // Secure processing with error handling
        ProcessingSuccess := ProcessRecordSecurely(RecordRef, TempProcessingBuffer);

    except
        ErrorOccurred := true;
    end;

    // Always cleanup, even in error scenarios
    TempProcessingBuffer.DeleteAll();

    if ErrorOccurred then
        exit(false);

    exit(ProcessingSuccess);
end;
```

### Session-Isolated Temporary Processing
```al
procedure SessionSafeProcessing(UserID: Code[50]): Boolean
var
    TempUserBuffer: Record User temporary;
    SessionGuid: Guid;
begin
    // Create session-specific identifier
    SessionGuid := CreateGuid();

    // Validate current user permissions
    if (UserID <> UserId) and (not UserPermissions.CanViewOtherUsers()) then
        exit(false);

    try
        // Session-isolated temporary data
        TempUserBuffer.Init();
        TempUserBuffer."User Security ID" := SessionGuid;
        TempUserBuffer."User Name" := UserID;
        TempUserBuffer.Insert();

        // Process with session context
        exit(ProcessUserInSession(TempUserBuffer, SessionGuid));

    finally
        // Session cleanup
        TempUserBuffer.DeleteAll();
    end;
end;
```

### Audit-Compliant Temporary Processing
```al
procedure AuditSafeProcessing(DocumentNo: Code[20]): Boolean
var
    SalesHeader: Record "Sales Header";
    TempAuditBuffer: Record "Change Log Entry" temporary;
    AuditEntryNo: Integer;
begin
    // Permission and audit validation
    if not UserPermissions.CanViewDocument(DocumentNo) then begin
        LogSecurityEvent('Unauthorized access attempt', DocumentNo);
        exit(false);
    end;

    if not SalesHeader.Get(SalesHeader."Document Type"::Order, DocumentNo) then
        exit(false);

    try
        // Create audit trail for temporary data access
        AuditEntryNo := CreateAuditEntry('Temporary Processing', DocumentNo);

        // Limited temporary data with audit context
        TempAuditBuffer.Init();
        TempAuditBuffer."Entry No." := AuditEntryNo;
        TempAuditBuffer."Table No." := Database::"Sales Header";
        TempAuditBuffer."Primary Key Field 1 Value" := DocumentNo;
        TempAuditBuffer.Insert();

        // Audited processing
        exit(ProcessWithAuditTrail(SalesHeader, TempAuditBuffer));

    finally
        // Cleanup with audit completion
        TempAuditBuffer.DeleteAll();
        CompleteAuditEntry(AuditEntryNo);
    end;
end;
```

### Memory-Efficient Cleanup
```al
procedure LargeDatasetProcessing(FilterText: Text): Boolean
var
    SourceRecord: Record "Item Ledger Entry";
    TempProcessingBuffer: Record "Item Ledger Entry" temporary;
    BatchSize: Integer;
    ProcessedCount: Integer;
begin
    BatchSize := 1000; // Process in batches to manage memory

    SourceRecord.SetFilter("Item No.", FilterText);
    if not SourceRecord.FindSet() then
        exit(false);

    repeat
        try
            // Process in batches with cleanup
            ProcessedCount := 0;
            repeat
                TempProcessingBuffer := SourceRecord;
                TempProcessingBuffer.Insert();
                ProcessedCount += 1;

                // Batch boundary cleanup
                if ProcessedCount >= BatchSize then begin
                    ProcessBatch(TempProcessingBuffer);
                    TempProcessingBuffer.DeleteAll();
                    ProcessedCount := 0;
                end;

            until (SourceRecord.Next() = 0) or (ProcessedCount >= BatchSize);

            // Process remaining records
            if ProcessedCount > 0 then
                ProcessBatch(TempProcessingBuffer);

        finally
            // Always cleanup batch data
            TempProcessingBuffer.DeleteAll();
        end;

    until SourceRecord.Next() = 0;

    exit(true);
end;
```

## Security Guidelines

1. **Validate permissions before populating temporary tables with sensitive data**
2. **Use try-finally blocks to ensure cleanup even in error scenarios**
3. **Apply session isolation to prevent cross-user data leakage**
4. **Implement audit trails for temporary access to sensitive information**
5. **Process large datasets in batches with regular cleanup**
6. **Document temporary table security requirements and cleanup procedures**