bcquality/microsoft/knowledge/data-modeling/do-not-change-primary-key.md
Michael Dieringer cc7c1f2ee0 Address Jesper Schulz-Wedde's review on PR #156
- Rename 3 articles so their .good.al/.bad.al companion stems match
  (do-not-change-primary-key, testfield-required-setup-field,
  al-identifiers-english), fixing the R14 orphan-sample errors.
- do-not-change-primary-key.good.al: include Flow in the new table's
  own primary key so it actually models the discriminating dimension.
- al-build-output-must-not-pollute-project-root.md: drop the
  unsubstantiated AL0197 causal claim and the non-existent
  al.outputPath setting; reframe as build-artifact hygiene sourced
  from ALTool --outfolder / al_build outputPath.
- prefer-email-module.md: Email Message is Codeunit 8904, not a table;
  distinguish it from the underlying Sent/Outbox/Draft storage.
- file-datatype-saas.md: File.Open/Create/Read/Write fails to compile
  against a Cloud-scoped project, it does not compile and silently
  fail at runtime.
- namespace-must-be-verified-from-source.md: narrow to "resolve from
  the referenced object's source or symbols," since source-file line
  one is not the only authoritative source (symbol packages, comments
  before the namespace line).
- test-data-must-be-random-and-complete.md: drop "assume an empty
  database" and "collision-free" absolutes; reframe around
  independence from unrelated business records and reserving explicit
  values for scenario-defining inputs.
- binary-choice-must-be-boolean.md: scope to genuine true/false
  semantics, not mechanical two-member-enum-to-boolean conversion.
- document-report-word-layout.md: scope down to a sourced Microsoft
  Learn recommendation instead of an unconditional performance
  guarantee; cite the three Learn pages.
- Wire the new articles into their review skills' candidate-selection
  signals (file-datatype-saas, prefer-email-module,
  namespace-must-be-verified-from-source, var-parameters-require-an-
  addressable-variable) so they can actually enter a worklist.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
2026-09-21 22:25:26 +02:00

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Markdown

---
bc-version: [all]
domain: data-modeling
keywords: [primary-key, clustered-key, table-design, appsource, breaking-change, schema-upgrade]
technologies: [al]
countries: [w1]
application-area: [all]
---
# Never Change a Published Table's Primary or Clustered Key Field List
> Contributions welcome — open a PR to refine or extend this article.
## Description
Once a table has shipped — to AppSource, or to any customer environment that has already upgraded onto it — its primary key, and any other key marked `Clustered = true`, is frozen. This includes adding a field to the key, not only removing or reordering one: Business Central identifies existing rows by their key value, so any change to which fields compose that key invalidates every row already stored under the old shape, and the platform's upgrade validation rejects it outright (`AS0009`). This is easy to trip over because it doesn't look like the well-known "don't delete a field" mistake — the field being added is often brand new, and folding a new discriminating dimension straight into the existing key feels like the natural, un-denormalized way to model it. On an unpublished table that is correct; on a published one it is a breaking schema change regardless of which direction the field list changed, and there is no in-place fix once the upgrade is rejected, only reverting the key to its published shape.
## Best Practice
Leave a published table's key exactly as shipped. Model a new discriminating dimension as a separate table with its own key instead of adding a field to the existing key, and branch orchestration code by the new dimension rather than filtering one shared table on an extra key field.
See sample: `do-not-change-primary-key.good.al`.
## Anti Pattern
Adding a field to a published table's primary or clustered key to distinguish a new case. This fails AppSource validation or any customer upgrade with `AS0009` as soon as rows already exist under the old key shape, whether the field is being added, removed, or reordered.
See sample: `do-not-change-primary-key.bad.al`.