Add TableRelation field-length and RecordRef.Open Temp knowledge

- data-modeling: tablerelation-field-length-must-match-related-field
  (exact length for unconditional relations, at least the longest target
  when all relations are conditional; no compile-time diagnostic)
- testing: recordref-open-temp-parameter-defeats-real-table-checks
  (a temp-opened RecordRef is empty, so existence/uniqueness checks on it
  never see persisted rows; cross-links use-generateguid article)
- Wire both into the review leaves and register the fixture pairs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

microsoft/knowledge/testing/recordref-open-temp-parameter-defeats-real-table-checks.bad.al

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+codeunit 50150 "Sample Payment Terms Codes"
+{
+    procedure GenerateUnusedPaymentTermsCode(): Code[10]
+    var
+        PaymentTerms: Record "Payment Terms";
+        LibraryUtility: Codeunit "Library - Utility";
+        RecRef: RecordRef;
+        FieldRef: FieldRef;
+        NewCode: Code[10];
+    begin
+        // Temp = true: RecRef is an empty temporary instance, so IsEmpty()
+        // is true on the first pass and existing Payment Terms are never seen.
+        RecRef.Open(Database::"Payment Terms", true, CompanyName());
+        FieldRef := RecRef.Field(PaymentTerms.FieldNo(Code));
+        repeat
+            NewCode := CopyStr(LibraryUtility.GenerateRandomXMLText(MaxStrLen(NewCode)), 1, MaxStrLen(NewCode));
+            FieldRef.SetRange(NewCode);
+        until RecRef.IsEmpty();
+        exit(NewCode);
+    end;
+}

microsoft/knowledge/testing/recordref-open-temp-parameter-defeats-real-table-checks.good.al

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+codeunit 50150 "Sample Payment Terms Codes"
+{
+    procedure GenerateUnusedPaymentTermsCode(): Code[10]
+    var
+        PaymentTerms: Record "Payment Terms";
+        LibraryUtility: Codeunit "Library - Utility";
+        RecRef: RecordRef;
+        FieldRef: FieldRef;
+        NewCode: Code[10];
+    begin
+        // Temp = false: the loop checks the persisted Payment Terms rows.
+        RecRef.Open(Database::"Payment Terms", false, CompanyName());
+        FieldRef := RecRef.Field(PaymentTerms.FieldNo(Code));
+        repeat
+            NewCode := CopyStr(LibraryUtility.GenerateRandomXMLText(MaxStrLen(NewCode)), 1, MaxStrLen(NewCode));
+            FieldRef.SetRange(NewCode);
+        until RecRef.IsEmpty();
+        exit(NewCode);
+    end;
+
+    procedure GetFieldFilterFromView(TableNo: Integer; TableView: Text; FieldNo: Integer): Text
+    var
+        RecRef: RecordRef;
+        FieldRef: FieldRef;
+    begin
+        // Temp = true is correct here: the RecordRef only parses a view and
+        // never reads rows.
+        RecRef.Open(TableNo, true);
+        RecRef.SetView(TableView);
+        FieldRef := RecRef.Field(FieldNo);
+        exit(FieldRef.GetFilter());
+    end;
+}

microsoft/knowledge/testing/recordref-open-temp-parameter-defeats-real-table-checks.md

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+---
+bc-version: [all]
+domain: testing
+keywords: [recordref, open, temporary, isempty, existence-check, uniqueness]
+technologies: [al]
+countries: [w1]
+application-area: [all]
+---
+
+# RecordRef.Open with Temp = true cannot check the real table
+
+## Description
+
+`RecordRef.Open(No: Integer [, Temp: Boolean] [, CompanyName: Text])` always takes a real table number. When `Temp` is `true`, though, the `RecordRef` refers to a temporary instance of that table. That instance starts empty and never contains the persisted rows. Microsoft Learn's example opens table 27 temporarily and notes that `Find('-')` "returns false" because "there are no records in a temporary table". So `IsEmpty`, `Find*`, `Get` or `Count` on a temp-opened `RecordRef` only sees rows the same code inserted into it. These calls can't answer "does this value already exist in the table?"
+
+The defect is easy to miss at the call site. `Temp` is a positional, unnamed Boolean, the table number is genuine, and the code compiles without a diagnostic. The usual shape is a generate-until-unused loop: the code sets a range on a field and repeats `until RecRef.IsEmpty()`. That loop exits on its first pass and returns a value that may already exist. The defect then shows up later as a duplicate-key error or a wrong lookup, often only once the table holds data.
+
+The shape occurs wherever `RecordRef` is used. This article sits in the testing domain because generic test-library helpers, which work on any table number, are where it typically appears. For how specific `LibraryUtility` helpers behave, including `GenerateRandomCode`'s temporary open, see [`use-generateguid-for-unique-test-fixture-values.md`](use-generateguid-for-unique-test-fixture-values.md). That article owns guidance on which helper to call.
+
+## Best Practice
+
+When the code that follows has to see persisted rows, open with `Temp = false` or omit the parameter. Learn's first example omits it so the table "will not be open as temporary table".
+
+`Temp = true` is correct when the `RecordRef` is deliberately a scratch instance that never answers existence questions about the real table, for example:
+
+- A field-validation sandbox: insert a temporary row, then `Validate` a field on it.
+- Parsing a table view with `SetView` and reading `GetFilter`.
+- Reading table metadata such as `SystemIdNo`.
+
+See sample: [`recordref-open-temp-parameter-defeats-real-table-checks.good.al`](recordref-open-temp-parameter-defeats-real-table-checks.good.al).
+
+## Anti Pattern
+
+`RecRef.Open(<table>, true[, ...])` followed, on the same `RecordRef` and with no `Insert` into it, by `IsEmpty`, `Find`, `FindFirst`, `FindSet`, `Get` or `Count` whose result decides whether a value already exists in the table. The classic case is a uniqueness loop ending `until RecRef.IsEmpty()`.
+
+See sample: [`recordref-open-temp-parameter-defeats-real-table-checks.bad.al`](recordref-open-temp-parameter-defeats-real-table-checks.bad.al).
+
+## Source
+
+- [RecordRef.Open method](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/developer/methods-auto/recordref/recordref-open-method): the syntax, Example 1 (parameters omitted, not temporary) and Example 2 (temporary open is empty, `Find('-')` returns false).
+- BCApps [`src/Layers/W1/Tests/ApplicationTestLibrary/LibraryUtility.Codeunit.al`](https://github.com/microsoft/BCApps/blob/main/src/Layers/W1/Tests/ApplicationTestLibrary/LibraryUtility.Codeunit.al): `GenerateRandomCode` opens with `true` at line 288 and loops `until RecRef.IsEmpty()`. `GenerateRandomCodeWithLength` opens with `false` at line 309.
+- Legitimate `Temp = true` uses in BCApps W1:
+  - [`src/Layers/W1/BaseApp/Inventory/Item/ItemTempl.Table.al`](https://github.com/microsoft/BCApps/blob/main/src/Layers/W1/BaseApp/Inventory/Item/ItemTempl.Table.al) line 1255: temporary `Item` insert plus `Validate`.
+  - [`src/Apps/W1/Quality Management/app/src/Utilities/QltyFilterHelpers.Codeunit.al`](https://github.com/microsoft/BCApps/blob/main/src/Apps/W1/Quality%20Management/app/src/Utilities/QltyFilterHelpers.Codeunit.al) line 942: `SetView` plus `GetFilter`.
+  - [`src/Layers/W1/BaseApp/Integration/SynchEngine/IntegrationRecordSynch.Codeunit.al`](https://github.com/microsoft/BCApps/blob/main/src/Layers/W1/BaseApp/Integration/SynchEngine/IntegrationRecordSynch.Codeunit.al) line 221: `SystemIdNo`.