omnigraph/docs/maintenance.md
Claude 243c0c3464
Add internal-schema versioning + auto-migration for __manifest
The on-disk shape of `__manifest` is reconciled with the binary via a single
stamp + dispatcher in `db/manifest/migrations.rs`:

- `INTERNAL_MANIFEST_SCHEMA_VERSION = 2` declares the shape this binary writes.
- The on-disk stamp `omnigraph:internal_schema_version` lives in the manifest
  dataset's schema-level metadata (Lance `update_schema_metadata`).
- `migrate_internal_schema(&mut dataset)` walks `match`-arm steps forward from
  the on-disk stamp until it matches the binary, then returns. Idempotent.
- `init_manifest_repo` stamps the current version at creation; the publisher's
  open-for-write path runs pending migrations before reading state. Reads
  stay side-effect-free.
- Forward-version protection: a stamp higher than the binary's known version
  triggers a clear "upgrade omnigraph first" error so an old binary cannot
  clobber a newer schema.

Self-heals existing pre-MR-766 deployments by auto-applying the v1→v2 step:
the `lance-schema:unenforced-primary-key` annotation on `__manifest.object_id`
that engages Lance's row-level CAS at commit time. New repos created via
`init` are stamped at v2 immediately and don't need migration.

Adding a future on-disk shape change is one constant bump, one match arm in
`migrate_internal_schema`, and one test — no new branches in unrelated code
paths. Code outside the migration module never inspects the stamp.

New tests in `manifest/tests.rs`:
- `test_init_stamps_internal_schema_version`
- `test_publish_migrates_pre_stamp_manifest_to_current_version`
- `test_publish_rejects_manifest_stamped_at_future_version`

Docs: `docs/storage.md`, `docs/maintenance.md`, `docs/constants.md` updated
per the AGENTS.md maintenance contract.
2026-04-29 11:44:14 +00:00

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1.8 KiB
Markdown

# Maintenance: Optimize & Cleanup
`db/omnigraph/optimize.rs`.
## `optimize_all_tables(db)` — non-destructive
- Lance `compact_files()` on every node + edge table on `main`.
- Rewrites small fragments into fewer large ones; old fragments remain reachable via older manifests.
- Bounded by `OMNIGRAPH_MAINTENANCE_CONCURRENCY` (default 8).
- Returns `[TableOptimizeStats { table_key, fragments_removed, fragments_added, committed }]`.
## `cleanup_all_tables(db, options)` — destructive
- Lance `cleanup_old_versions()` per table.
- Removes manifests (and their unique fragments) older than the retention policy.
- `CleanupPolicyOptions { keep_versions: Option<u32>, older_than: Option<Duration> }` — at least one is required.
- Returns `[TableCleanupStats { table_key, bytes_removed, old_versions_removed }]`.
- CLI guards with `--confirm`; without it, prints a preview line.
## Tombstones
Logical sub-table delete markers in `__manifest`; `tombstone_object_id(table_key, version)` excludes a sub-table version from snapshot reconstruction.
## Internal schema migrations (`db/manifest/migrations.rs`)
Version evolutions of the on-disk `__manifest` shape are reconciled automatically on the first write under a new binary. `INTERNAL_MANIFEST_SCHEMA_VERSION` declares the shape the binary expects; the on-disk stamp `omnigraph:internal_schema_version` (Lance schema-level metadata) records the on-disk shape. The publisher's open-for-write path calls `migrate_internal_schema` before reading state; reads are side-effect-free. No operator action is required for in-place upgrades. See [storage.md → Internal schema versioning](storage.md) for the full mechanism.
A binary opening a manifest stamped at a version *higher* than it knows about refuses to publish with a clear "upgrade omnigraph first" error — old binaries cannot clobber a newer schema.