bcquality/community/knowledge/data-modeling/validate-table-relation-false-suppresses-rename-propagation.bad.al
Stefan Maron e00ef8ad94 knowledge(data-modeling): TableRelation delete/rename asymmetry and the xRec before-image contract
Three related concerns, each proven by executable tests rather than recall.
They were extracted from a real defect that shipped through a six-reviewer
panel undetected, which is the admission test passing on behavior rather than
on theory.

owning-table-must-delete-dependents-in-ondelete
  AL has no cascading delete. What makes it missable is an asymmetry: the
  platform DOES keep references correct on rename via TableRelation, so a
  developer who learns that and generalizes it to delete ships orphans. Also
  notes the permission trap (delete rights needed on the dependent table, not
  just the parent).

validate-table-relation-false-suppresses-rename-propagation
  The non-obvious half. The property name implies input validation only, but
  disabling it also switches off rename propagation. Verified against a parent
  renamed once while a child held three fields: a normal relation (follows),
  the same relation with validation disabled (does NOT follow), and a field
  with no relation at all (does not follow) — the third being the control that
  proves the test can detect a non-propagating field.

xrec-is-a-before-image-only-in-some-triggers
  Corrects both the naive belief that xRec is always the previous record and
  the folk rule that it 'only works from a page'. The behavior is per-trigger:
  a genuine before-image in OnRename and OnDelete regardless of driver, a
  mirror of Rec in OnInsert/OnModify when driven from code, and a real
  before-image in those two only when a page drove the write. That last
  asymmetry is why an OnModify comparison against xRec passes manual page
  testing and silently no-ops in a job queue.

Targets /community per CONTRIBUTING — general BC knowledge, not fork-specific.
Frontmatter validator clean; Test-ReviewFixtures passes (32 cases, 16 leaves).
2026-08-05 13:46:41 +02:00

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1.1 KiB
AL

table 50121 "Document Link"
{
fields
{
field(1; "Entry No."; Integer)
{
DataClassification = CustomerContent;
}
field(2; "Document No."; Code[20])
{
DataClassification = CustomerContent;
TableRelation = "Source Document"."No.";
// Added to silence a validation error while the row is staged, before
// the Source Document exists. The relation is still declared, so this
// reads as harmless — but it also switches OFF rename propagation.
// Renaming a Source Document now leaves this field on the old key,
// with no error, and nothing else maintains it.
ValidateTableRelation = false;
}
// Composite value: no TableRelation is possible, and no OnRename on the
// owning table maintains it either. Rots the same way, for the other reason.
field(3; "Source Key"; Code[50])
{
DataClassification = CustomerContent;
}
}
keys
{
key(PK; "Entry No.")
{
Clustered = true;
}
}
}