Bound commit checkpoints by key range

Use a capped ordered query to discover each checkpoint watermark before locking and processing only that key range.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 85be3fc4-5253-47b8-ba1b-6b8fd188fcea

microsoft/knowledge/performance/avoid-commit-inside-loops.good.al

@@ -1,3 +1,17 @@
+query 50127 "Perf Customer Chunk"
+{
+    QueryType = Normal;
+    OrderBy = ascending(CustomerNo);
+
+    elements
+    {
+        dataitem(Customer; Customer)
+        {
+            column(CustomerNo; "No.") { }
+        }
+    }
+}
+
 codeunit 50128 "Perf Sample CommitInLoop Good"
 {
     procedure NormalizeCustomerNames()
@@ -5,28 +19,45 @@ codeunit 50128 "Perf Sample CommitInLoop Good"
         LastCustomerNo: Code[20];
     begin
         // The outer loop owns checkpoints; the per-row loop contains no Commit.
-        while NormalizeNextChunk(LastCustomerNo, 500) do
+        while NormalizeNextChunk(LastCustomerNo) do
             Commit();
     end;
 
-    local procedure NormalizeNextChunk(var LastCustomerNo: Code[20]; ChunkSize: Integer): Boolean
+    local procedure NormalizeNextChunk(var LastCustomerNo: Code[20]): Boolean
     var
         Customer: Record Customer;
-        RowsInChunk: Integer;
+        CustomerChunk: Query "Perf Customer Chunk";
+        FirstCustomerNo: Code[20];
+        LastChunkCustomerNo: Code[20];
     begin
-        Customer.SetCurrentKey("No.");
+        CustomerChunk.TopNumberOfRows(500);
         if LastCustomerNo <> '' then
-            Customer.SetFilter("No.", '>%1', LastCustomerNo);
-        if not Customer.FindSet(true) then
+            CustomerChunk.SetFilter(CustomerNo, '>%1', LastCustomerNo);
+        CustomerChunk.Open();
+        if not CustomerChunk.Read() then begin
+            CustomerChunk.Close();
             exit(false);
+        end;
+
+        FirstCustomerNo := CustomerChunk.CustomerNo;
+        repeat
+            LastChunkCustomerNo := CustomerChunk.CustomerNo;
+        until not CustomerChunk.Read();
+        CustomerChunk.Close();
+
+        Customer.SetCurrentKey("No.");
+        Customer.SetRange("No.", FirstCustomerNo, LastChunkCustomerNo);
+        if not Customer.FindSet(true) then begin
+            LastCustomerNo := LastChunkCustomerNo;
+            exit(true);
+        end;
 
         repeat
             Customer.Name := UpperCase(Customer.Name);
             Customer.Modify();
-            LastCustomerNo := Customer."No.";
-            RowsInChunk += 1;
-        until (RowsInChunk >= ChunkSize) or (Customer.Next() = 0);
+        until Customer.Next() = 0;
 
+        LastCustomerNo := LastChunkCustomerNo;
         exit(true);
     end;
 }

microsoft/knowledge/performance/avoid-commit-inside-loops.md

@@ -1,7 +1,7 @@
 ---
 bc-version: [all]
 domain: performance
-keywords: [commit, loop, transaction, lock, checkpoint, codeunit-run]
+keywords: [commit, loop, transaction, lock, checkpoint, bounded, watermark, topnumberofrows, codeunit-run]
 technologies: [al]
 countries: [w1]
 application-area: [all]
@@ -13,11 +13,11 @@ application-area: [all]
 
 ## Description
 
-Commit ends the current write transaction. Calling it inside a per-row loop produces one transaction per iteration and loses the ability to roll back the whole operation atomically; it also interferes with the platform's ability to batch write operations. Most loops need no explicit Commit at all — AL auto-commits the enclosing code module on successful completion (see `understand-implicit-transaction-boundary.md`). When the batch is too large for one transaction, the fix is not a per-row Commit but bounded checkpoints that each process N rows.
+Commit ends the current write transaction. Calling it inside a per-row loop produces one transaction per iteration and loses the ability to roll back the whole operation atomically; it also interferes with the platform's ability to batch write operations. Most loops need no explicit Commit at all — AL auto-commits the enclosing code module on successful completion (see `understand-implicit-transaction-boundary.md`). When the batch is too large for one transaction, the fix is not a per-row Commit but bounded checkpoints that each retrieve and process the next N rows.
 
 ## Best Practice
 
-If the batch is large enough that a single transaction is untenable, use an outer loop that selects and finishes the next N rows. Commit only after the inner row loop has returned and the checkpoint state identifies where the next chunk starts. A `Codeunit.Run` boundary can also own a chunk when its implicit commit and error behavior fit the caller — see `codeunit-run-as-atomic-sub-operation.md`.
+If the batch is large enough that a single transaction is untenable, use an ordered primary-key watermark and retrieve a bounded next-N window. `FindSet` is optimized for reading the complete filtered set and isn't implemented as `TOP X`, so calling it over the remaining tail and breaking after N rows does not bound retrieval. The sample uses a query capped by [`TopNumberOfRows`](https://learn.microsoft.com/en-us/dynamics365/business-central/dev-itpro/developer/methods-auto/query/queryinstance-topnumberofrows-method) to discover the next upper key, then locks and processes only that key range. Commit after the bounded inner loop returns and persist its upper key as the next watermark. Use a stable key and define how a later run handles records inserted at or below an already committed watermark. A `Codeunit.Run` boundary can also own a chunk when its implicit commit and error behavior fit the caller — see `codeunit-run-as-atomic-sub-operation.md`.
 
 See sample: `avoid-commit-inside-loops.good.al`.