After a substrate audit of the Lance data-evolution guide on
2026-05-13, the v1 plan was simplified. Two key findings:
1. Lance's `drop_columns()` is already metadata-only and reversible
via time travel until cleanup. No need for a parallel
`tombstoned: bool` field in our catalog IR — Lance's version
graph IS the tombstone.
2. The full schema_apply substrate migration (add_columns,
drop_columns, alter_columns vs. stage_overwrite across all step
types) is consolidated in MR-948 as a sibling issue. v1 only
uses the relevant slice (drop_columns for OG-DS-1XX).
Net plan changes:
- Commit 3 (original): tombstone fields on catalog IR → dropped.
No catalog IR change needed. The Lance drop_columns commit IS the
tombstone.
- Commit 5 (original): apply path writes tombstoned: true → replaced
with: apply path calls Dataset::drop_columns([name]).
- Commit 7 Hard mode: stage_overwrite removing the column → replaced
with: drop_columns + compact_files + cleanup_old_versions. Same
APIs omnigraph cleanup already uses.
- Commit 8 (original): omnigraph schema unhide → dropped. Time
travel is the undo (omnigraph snapshot --at <commit>).
Net result: 8 commits → 5 commits. ~250 LoC less surface. More
substrate-aligned.
The chassis types from commit 2 (DropMode enum, DropType /
DropProperty variants) are kept exactly as designed; only the
implementation strategy changed.
The Lance docs quote is included in the doc so future readers see
the substrate behavior cited verbatim.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
First commit of the chassis v1 branch. Lands a small, foundational
slice without behavior change, plus a planning doc that lays out the
remaining 7 commits in sequence so the PR can be reviewed
incrementally.
This commit:
- Adds SchemaMigrationStep::diagnostic() returning the full
&'static DiagnosticCode (family + tier + severity) for
UnsupportedChange steps with codes. Renderers can now reach the
tier without re-implementing the code → tier lookup.
- CLI `omnigraph schema plan` output now displays tier alongside
code:
unsupported change on node:Person.age [OG-DS-104, destructive]:
removing property 'Person.age' is not supported in schema
migration v1
Operators see at-a-glance the kind of risk each rejection
represents — not just the rule identifier.
- No behavior change. All 11 existing schema_apply tests still pass.
Planning doc at docs/schema-lint-v1-plan.md tracks the 7 remaining
commits to bring v1 to feature-complete:
1. (this commit) Tier surfacing in plan output.
2. Soft / Hard mode enum on drop steps.
3. Tombstone fields on catalog IR.
4. Planner emits DropProperty { Soft } by default.
5. Apply path implements Soft mode.
6. Convert PR #62 destructive-rejection tests.
7. --allow-data-loss flag + Hard mode.
8. (optional) Tombstone unhide / restore command.
Delete the planning doc when v1 lands. Intentionally checked in to
the WIP branch so the scope is reviewable; not intended as a
permanent doc.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
