omnigraph/docs/user/maintenance.md
Ragnor Comerford e62d9166fb
fix: optimize publishes compaction; recovery roll-back converges manifest (#141)
* test(optimize): cover manifest publish + HEAD-drift reconcile

Red against the pre-fix optimize, which ran compact_files without
publishing the compacted version to __manifest:

- maintenance: optimize must publish so the manifest table_version
  tracks the compacted Lance HEAD and a later schema apply succeeds;
  and must reconcile a pre-existing manifest-behind-HEAD drift (forged
  via raw Lance compaction) so strict writes commit again.
- end_to_end + composite_flow: post-optimize query / strict update /
  reopen in the full lifecycle (the canonical flow previously omitted
  post-optimize writes as a documented "known limitation").
- failpoints: a crash between compaction and the manifest publish rolls
  forward on next open.

* fix(optimize): publish compaction to manifest and reconcile HEAD drift

optimize ran Lance compact_files without publishing the new version to
__manifest, so the manifest table_version lagged the Lance HEAD: reads
stayed pinned to the pre-compaction version, and the next schema apply or
strict update/delete failed its HEAD-vs-manifest precondition with
"stale view ... refresh and retry" (open-time recovery rollback inflated
the gap on retry).

optimize now publishes each compacted table's version under the
per-(table, main) write queue, guarded by a manifest CAS and a
SidecarKind::Optimize recovery sidecar (loose-match; roll-forward is safe
because compaction is content-preserving). When a table has nothing left
to compact but its Lance HEAD is already ahead of the manifest pin
(pre-fix drift, or a recovery restore commit), optimize reconciles the
manifest forward to HEAD (metadata-only, no sidecar). Caches and the
CSR/CSC graph index are invalidated after a publish.

Docs updated (maintenance, storage, branches-commits, writes, testing).

* test(recovery): rollback convergence + optimize-defer regressions

Red against the current code, landed before the fix:
- recovery: after the open-time sweep rolls a sidecar back, the manifest
  must track Lance HEAD (no residual drift) so a follow-up schema apply
  succeeds — the original "+1 per retry" loop. Today roll-back restores
  without publishing, so the manifest lags HEAD and the apply fails its
  HEAD-vs-manifest precondition.
- maintenance: optimize must refuse while a recovery sidecar is pending —
  operating on an unrecovered graph could publish a partial write the
  sweep would roll back.

Also removes optimize_reconciles_preexisting_manifest_head_drift: the
ad-hoc drift reconcile it covered is replaced by recovery-side convergence.

* fix(recovery): converge manifest on roll-back; optimize defers on pending recovery

Root of PR #141's review findings and the original "+1 per retry" loop:
a Lance HEAD ahead of the manifest was ambiguous (benign content-preserving
drift vs. a partial write a sidecar will roll back), and optimize's reconcile
guessed it benign. Close the class instead of guessing:

- Recovery roll-back now PUBLISHES the restored version (via a
  push_table_update_at_head helper shared with roll-forward), so the manifest
  tracks the Lance HEAD after recovery — symmetric with roll-forward. This
  fixes the +1 loop (after one roll-back the retry's HEAD-vs-manifest
  precondition passes) and removes the only remaining source of orphaned
  drift. The audit still records the logical rolled-back-to version; the
  manifest is published at the restore commit (identical content).
- optimize drops the ad-hoc drift reconcile and instead REFUSES when a
  __recovery sidecar is pending, so it only ever operates on a recovered
  graph (manifest == HEAD); its compaction publish can no longer commit a
  partial write. With the reconcile gone, the blob-skip-vs-reconcile gap is
  moot.

Updates the rollback recovery-test helper (manifest == HEAD after roll-back),
the failpoints assertions, and the user/dev docs.

* test(recovery): fix rollback assertion for manifest convergence

The roll-back-publishes change makes the manifest version advance after a
SchemaApply roll-back (to the old-schema content), so the
schema_apply_without_schema_staging_rolls_back_on_next_open assertion must
be `version > pre`, not `version == pre`. This update was dropped during
the commit churn and surfaced as a CI Test Workspace failure; the
old-schema-preserved intent stays covered by count_rows + _schema.pg + the
RolledBack convergence invariant.
2026-06-08 02:50:12 +03:00

38 lines
5.3 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`, then **publishes the compacted version to the `__manifest`** so the manifest's `table_version` tracks the compacted Lance HEAD. Reads pin the manifest version, so without this publish compaction would be invisible to readers *and* would break the HEAD-vs-manifest precondition of the next schema apply / strict update/delete ("stale view … refresh and retry"). The publish advances the graph version (a system-attributed commit) only for tables that actually compacted.
- Rewrites small fragments into fewer large ones; old fragments remain reachable via older manifests until `cleanup` runs.
- Each table's compact→publish runs under its per-`(table, main)` write queue (serializing with concurrent mutations — compaction is a Lance `Rewrite` op that retryable-conflicts with a concurrent merge/update/delete on overlapping fragments). The Lance-HEAD-before-manifest-publish gap is covered by a `SidecarKind::Optimize` recovery sidecar (loose-match): a crash in that window rolls the compacted version forward on the next `Omnigraph::open` (compaction is content-preserving, so roll-forward is always safe).
- **Requires a recovered graph.** `optimize` refuses (errors) when an unresolved recovery sidecar is present under `__recovery` — operating on an unrecovered graph could publish a partial write the open-time recovery sweep would roll back. Reopen the graph to run the recovery sweep, then re-run `optimize`. (Recovery roll-back now publishes its restored version, so a recovered graph always satisfies `manifest == Lance HEAD` going in; there is no leftover drift for `optimize` to interpret.)
- Bounded by `OMNIGRAPH_MAINTENANCE_CONCURRENCY` (default 8).
- Returns `[TableOptimizeStats { table_key, fragments_removed, fragments_added, committed, skipped }]`.
- **Blob tables are skipped.** A table that declares any `Blob` property is not compacted: it is reported with `skipped: Some(BlobColumnsUnsupportedByLance)` (and logged via `tracing::warn`) instead of compacted, and the rest of the sweep proceeds normally. The current Lance `compact_files` mis-decodes blob-v2 columns under its forced `BlobHandling::AllBinary` read; **reads and writes are unaffected** — only compaction is. This is gated by `LANCE_SUPPORTS_BLOB_COMPACTION` (`db/omnigraph/optimize.rs`) and removed when the upstream Lance fix lands (see [docs/dev/lance.md](../dev/lance.md)). Consequence: fragment count and deleted-row space on blob tables are not reclaimed until then; query results are never affected.
## `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, error }]`.
- **Fault-isolated per table.** A single table's transient failure (version GC or
orphan reclaim) is recorded on that table's stats row (`error: Some(..)`, logged
via `tracing`) and never aborts the healthy tables — cleanup is the convergence
backstop, so it does as much as it can and converges on re-run. The CLI reports
any failed tables; rerun `cleanup` to retry them.
- CLI guards with `--confirm`; without it, prints a preview line.
- **Recovery floor:** `--keep < 3` may garbage-collect Lance versions that the open-time recovery sweep needs as a rollback target (the sweep restores to the branch's manifest-pinned table version, which is HEAD-1 in the typical Phase B → Phase C drift case). Default `--keep 10` is safe.
- **Orphaned-branch reconciliation:** before the version GC, cleanup runs `reconcile_orphaned_branches`, which `force_delete_branch`es any per-table or commit-graph Lance branch absent from the manifest branch list. These orphans arise when a `branch_delete` flips the manifest authority but a downstream best-effort reclaim does not complete (see [branches-commits.md](branches-commits.md)). The reconciler is authority-derived and idempotent (it no-ops once nothing is orphaned), runs regardless of the `keep_versions` / `older_than` values (those gate version GC only), and never reclaims `main` or system-branch forks. Reclaimed forks are logged via `tracing::info`.
## 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.