omnigraph/docs/dev/index.md
Andrew Altshuler e98347eb7b
schema-lint chassis v1.0: DropProperty Soft + code-tagged diagnostics (MR-694) (#90)
* schema-lint chassis v1 (WIP): tier surfacing + plan doc

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>

* schema-lint v1 commit 2: DropMode + dormant Drop* variants

Second commit of the chassis v1 branch. Lands the type-level shape
of soft/hard drops without wiring them up. Variants are reachable
from emitters but the planner doesn't produce them yet; the apply
path returns an explicit not-yet-implemented error if one shows up
via deserialization.

Added:

- `DropMode { Soft, Hard }` — orthogonal to `SafetyTier`. Tier
  classifies the rule's risk class; mode is the operator's intent
  for data treatment.
    - `Soft` → catalog tombstone, data retained. Tier: safe.
    - `Hard` → Lance-level removal. Tier: destructive; will require
      --allow-data-loss to apply (commit 7).

- `SchemaMigrationStep::DropType { type_kind, name, mode }` and
  `SchemaMigrationStep::DropProperty { type_kind, type_name,
  property_name, mode }` variants.

- Re-export `DropMode` from `omnigraph_compiler::DropMode` so
  downstream crates don't reach into the catalog submodule.

- CLI `render_schema_plan_step` arms for both variants, surfacing
  the mode in plan output: `drop property 'Person.age' of node
  'Person' (soft mode)`.

- `apply_schema_with_lock` exhaustive match arm for the two new
  variants that returns `manifest_internal` with a clear
  not-yet-implemented message. If a SchemaIR JSON containing
  Drop{Type,Property} arrives (e.g. from a future tool or hand-
  written), the apply path fails explicitly rather than silently
  misclassifying.

- Two new in-source tests:
    - `drop_steps_round_trip_through_serde` — pins the wire shape
      for all four (variant × mode) combinations.
    - `drop_mode_serde_uses_snake_case` — pins external-tool-
      friendly serialization (`"soft"` / `"hard"`).

Build: clean, only pre-existing warnings.
Tests:
- omnigraph-compiler schema_plan: 6/6 (4 existing + 2 new).
- omnigraph-engine schema_apply: 11/11 (unchanged — planner still
  emits UnsupportedChange for removal paths).

Next commit (commit 3 per docs/schema-lint-v1-plan.md): add the
`tombstoned: bool` fields to NodeIR / EdgeIR / PropertyIR for the
catalog representation of soft-mode tombstones.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* plan doc: reframe v1 around Lance native drop_columns

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>

* schema-lint v1 commit 3: emit + apply DropProperty { Soft }

Wire the dormant DropProperty variant end-to-end for the Soft case.
Per docs/schema-lint-v1-plan.md, commit #3 of the schema-lint chassis
v1 series (MR-694).

Planner (schema_plan.rs):
- plan_properties: emit DropProperty { type_kind, type_name,
  property_name, mode: Soft } instead of UnsupportedChange when a
  property exists in accepted but not in desired. Plan is now
  supported = true for drop-only changes.

Apply (schema_apply.rs):
- Route DropProperty { Soft } through rewritten_tables. The existing
  batch_for_schema_apply_rewrite path already iterates the *target*
  schema fields, so a property absent from desired_catalog is
  naturally projected away. The prior Lance version retains the
  dropped column for time-travel reversibility (until cleanup runs).
- DropType still errors (lands in commit #4 with different mechanics:
  __manifest entry removal instead of column projection).
- DropProperty { Hard } still errors (lands in commit #5 with
  --allow-data-loss CLI flag + immediate compact_files +
  cleanup_old_versions).

Tests:
- Planner unit test plan_emits_soft_drop_for_removed_nullable_property
  asserts the variant emission + supported = true + no UnsupportedChange.
- Integration test apply_schema_drops_a_nullable_property_softly_
  preserves_prior_version (replaces the former
  apply_schema_rejects_dropping_a_property_with_data) asserts:
  (a) plan contains DropProperty { Soft }
  (b) apply succeeds + manifest advances + row count unchanged
  (c) current dataset schema lacks the dropped column
  (d) snapshot_at_version(pre_drop) still has the dropped column
  (e) reopen consistency — drop preserved across engine restart

Recovery: rides on SidecarKind::SchemaApply per MR-847. No new
sidecar kind needed; the entire apply path is already sidecar-wrapped.

Substrate alignment: this commit uses the stage_overwrite full-rewrite
path (full_rewrite cost class) rather than Lance native drop_columns
(catalog_only cost class). MR-948 is the follow-up substrate-alignment
refactor that introduces a LanceColumnOp surface and switches the
metadata-only case onto drop_columns. Functional outcome is identical;
cost-class improvement deferred.

Test results:
- cargo test -p omnigraph-compiler --lib: 238 passed
- cargo test -p omnigraph-engine --test schema_apply: 11 passed

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* docs: move schema-lint-v1-plan into docs/dev/ + add to index

Post-rebase fixup for the docs split (#93). The plan doc was added
to docs/ at the top level before main reorganized to docs/{user,dev}/.
This moves it into docs/dev/ and adds an entry to docs/dev/index.md
under a new "Active Implementation Plans" section so the
check-agents-md.sh link check passes.

Per the original commit message (617a77d), the plan doc is intentionally
temporary — it will be deleted when v1 lands.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-05-16 16:30:03 +03:00

2.9 KiB

Developer Docs

Audience: contributors, maintainers, and coding agents

This is the contributor-facing entry point. These docs explain architecture, invariants, implementation contracts, test ownership, and upstream Lance constraints. User-facing behavior should still be documented through docs/user/index.md and the relevant public reference docs.

Required For Every Non-Trivial Change

Need Read
Architectural rules, known gaps, deny-list invariants.md
Upstream Lance source-of-truth index lance.md
Existing test coverage and test placement testing.md

Architecture And Storage

Area Read
System structure, L1/L2 framing, component diagrams architecture.md
On-disk layout, manifest schema, URI behavior storage.md
Direct-publish writes, D2, staged writes, recovery sidecars runs.md
Query execution, mutation execution, loader flow execution.md
Index lifecycle and graph topology indexes indexes.md
Branch and commit internals branches-commits.md
Three-way merge implementation and conflicts merge.md
Diff/change-feed implementation changes.md
Branch protection policy branch-protection.md
CODEOWNERS source of truth codeowners.md

Language, Runtime, And Boundaries

Area Read
Schema grammar, catalog, migration planner schema-language.md
Query grammar, IR, lints, mutation restrictions query-language.md
Embedding client and @embed integration embeddings.md
Cedar policy surface and server gating policy.md
Server auth, OpenAPI, endpoint handlers server.md
Error taxonomy and serialization errors.md
Constants and tunables constants.md
Transaction model public contract transactions.md

Project Operations

Area Read
CI and release workflows ci.md
Install and deployment packaging install.md, deployment.md
Release history releases/

Active Implementation Plans

Working documents for in-flight feature work. Removed when the work lands.

Area Read
Schema-lint chassis v1 (MR-694) — --allow-data-loss, soft/hard drops schema-lint-v1-plan.md

Boundary

Developer docs may mention implementation details, stale gaps, upstream Lance blockers, and review rules. User docs should not require that context unless the detail changes the public contract.