bcquality/microsoft/knowledge/breaking-changes/obsolete-table-fields-instead-of-deleting-them.md
Jesper Schulz-Wedde 186d8a1314
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Complete AL review knowledge readiness (#108)
* Complete AL review knowledge readiness

Fill telemetry and Query coverage, strengthen thin review domains, correct audited content defects, and add deterministic cheap-model evaluation and reference-integrity safeguards.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 9825b012-e653-496a-9310-c1f4b6f8ac27

* Generalize review fixture discovery

Derive smoke cases from the leaf, domain, and paired-sample conventions so new leaves require no scoring-contract changes. Keep only exceptional selection/context overrides and fail when retrieval metadata cannot rank the selected article.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 9825b012-e653-496a-9310-c1f4b6f8ac27

* Preserve published field IDs in sample

Keep the existing Email and Contact Email field IDs unchanged, clarify that the sample represents an independent baseline, and use a local breaking-change rule for the generic smoke evaluation.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 9825b012-e653-496a-9310-c1f4b6f8ac27

* Clarify published field identity rules

State explicitly that a published field keeps its ID, name, and type while a replacement is added as a separate field under an unused ID.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 9825b012-e653-496a-9310-c1f4b6f8ac27

* Align field obsoletion sample baselines

Use Email field ID 3 as the shared baseline so the bad example demonstrates a same-ID rename while the good example retains the original field and adds a separate replacement.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 9825b012-e653-496a-9310-c1f4b6f8ac27

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Co-authored-by: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com>
2026-07-15 10:55:25 +02:00

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---
bc-version: [all]
domain: breaking-changes
keywords: [table-field, obsoletestate, obsoletereason, obsoletetag, pending, removed, data-loss]
technologies: [al]
countries: [w1]
application-area: [all]
---
# Obsolete published table fields instead of deleting, renaming, or renumbering them
## Description
A shipped table field carries both a source-level contract and persisted data. Renaming a field while retaining its ID is prohibited by AppSourceCop AS0005 and can break dependent extensions, but it is not inherently a drop-and-readd operation and should not be described as automatic data loss. Deleting the field or replacing it under a different ID is the data-loss risk: the old field storage is no longer represented unless data is migrated. The supported path is to keep the old field and obsolete it, add a replacement under a new ID, and migrate values before later removal.
## Best Practice
Keep the old field's ID, name, and type unchanged. Add the replacement as a separate field under an unused ID, then mark the old field `ObsoleteState = Pending` with an `ObsoleteReason` that names the replacement and an `ObsoleteTag` recording the obsoletion version. Keep the old field readable so an upgrade codeunit can copy its data during the deprecation window. Move it to `ObsoleteState = Removed` only in a later release, after the window has passed and data has migrated.
See sample: `obsolete-table-fields-instead-of-deleting-them.good.al`.
## Anti Pattern
Renaming published `Email` to `Contact Email` with the same ID violates the compatibility contract and AS0005, even though the retained ID does not itself imply a fresh empty column. Deleting `Email` or changing its ID additionally risks losing its stored values. Detection: any previously shipped field whose name changes at the same ID, or whose original ID disappears without the unchanged field being retained as `Pending` and its data migrated to a separate replacement field.
See sample: `obsolete-table-fields-instead-of-deleting-them.bad.al`.