omnigraph/docs/user/reference/constants.md
Ragnor Comerford 7779b72446
feat(engine): retire commit-graph tables (#311)
* docs(dev): write-latency roadmap (validated cost model + layered fix)

Records the validated 6-LIST warm-write cost model, the two root causes
(un-GC'd _versions/; re-resolving latest by listing), and the layered fix
(GC + capture-once reuse), plus how commit-graph-table retirement feeds in.
Linked from docs/dev/index.md next to the RFC-013 docs.

* feat(engine)!: strand storage versioning — one internal-schema version, no in-place migration

Set MIN_SUPPORTED == CURRENT == 4: this binary reads exactly one `__manifest`
internal-schema version and refuses any older graph on open with a
rebuild-via-export/import message, instead of migrating it in place. Storage
format changes become a deliberate cutover, not a permanently-carried in-place
migration — the pre-release "complexity must be earned" contract.

Delete the entire in-place migration apparatus and everything that existed only
to support it: the `migrate_vN` arms + dispatcher + stamp-bump helpers + the
schema-version-floor tripwire; `migrate_on_open` (both open modes now refuse);
the legacy `_graph_commits.lance` readers + the v3 test fixtures + migration
tests + `migration.v3_to_v4.*` failpoints + the two surface guards that pinned
Lance variants only the migration matched on; and `state::merge_lineage_rows`.
Keep `read_stamp` / `stamp_current_version` / `set_stamp` /
`refuse_if_stamp_unsupported` — the seam a future one-shot converter plugs into.

`load_commit_cache_for_branch` now reads the `__manifest` projection
unconditionally (sub-v4 graphs are refused at open). Adds
`sub_current_graph_is_refused_on_open_with_rebuild_hint`.

The commit-graph TABLES are still created/used as branch-ref ledgers — their
retirement (CommitGraph -> pure `__manifest` projection) is the next commit.

BREAKING CHANGE: a graph created by omnigraph <= 0.7.2 (internal schema v3) is
refused on open. Rebuild it: `omnigraph export` with the old release, then
`omnigraph init` + `omnigraph load` with this one. Data, vectors, and blobs are
preserved; commit history and branches are not.

* feat(engine)!: retire `_graph_commits.lance` / `_graph_commit_actors.lance` — CommitGraph is a pure `__manifest` projection

Since RFC-013 Phase 7, graph lineage lives in `__manifest` (`graph_commit` /
`graph_head` rows) and branch authority is `__manifest` (branch create forks it
first). The two commit-graph datasets were vestigial: `_graph_commit_actors.lance`
was never written or read; `_graph_commits.lance` carried zero commit rows and
only mirrored the manifest's branch refs (a deny-list "parallel copy"). Retire
both.

- `CommitGraph` collapses to a pure projection: drops its Lance dataset handles
  (`dataset`/`actor_dataset`) and all branch methods; `open`/`open_at_branch`/
  `refresh`/`init` open NO dataset, building the cache from
  `ManifestCoordinator::read_graph_lineage_at`. Removes ~1.4s of cold-open
  dataset opens.
- `graph_coordinator`: `commit_graph` is now non-`Option` (always a valid
  projection). `branch_create`/`branch_delete` go through `ManifestCoordinator`
  only — a single atomic op, replacing the two-step manifest-fork +
  commit-graph-fork + rollback. Deleted `create_commit_graph_branch`,
  `reclaim_commit_graph_branch`, `ensure_commit_graph_initialized`, and every
  `storage.exists(_graph_commits.lance)` gate.
- `optimize`: dropped `reconcile_commit_graph_orphans` and the two tables from
  the internal-table compaction set (now `__manifest` only).
- `instrumentation`: `INTERNAL_TABLE_DIRS` no longer lists the two tables.
- Fresh graphs create neither table; `lineage_projection.rs` now asserts both
  `.lance` dirs are absent. Deleted the obsolete commit-graph-branch-race
  failpoint tests + their failpoint names, and updated the `maintenance`
  optimize tests (one internal table, not three).

Review-pass fixes folded in:
- Removed two stale `omnigraph.rs` in-source tests the prior run missed (a
  disk-full link failure masked them): one asserting `open` probes
  `_graph_commits.lance` (the exists-gate this commit removes) — it was masked
  earlier by a disk-full link failure.
- Corrected src comments referencing deleted code (`migrate_v3_to_v4`,
  `append_commit`/`append_merge_commit`, the three-internal-table list,
  the `_graph_commits` reconcile owner) in publisher/recovery/optimize/recovery_audit.
- Narrowed `set_stamp_for_test` to `cfg(test)` (its only caller is the refusal
  test) — removes a dead-code warning in the failpoints build.

Branch create/delete atomicity improves (single atomic `__manifest` op). No
behavior change for reads or branches.

Follow-up (separate commit): the now-always-0 `IoCounts::commit_graph_reads` test
counter + its `IOTracker`, threaded through ~11 cost-test files.

* feat: surface the internal-schema (storage-format) version to operators

After stranding storage versioning (a sub-v4 graph is refused on open), operators
could only discover the storage-format version by hitting a refusal. Surface it:

- `omnigraph version` prints an `internal-schema <N>` line (the binary's CURRENT
  storage-format version).
- `omnigraph snapshot` includes `internal_schema_version` — the GRAPH's per-branch
  on-disk stamp, read via the new `Omnigraph::internal_schema_version_of`.
- `GET /healthz` includes `internal_schema_version` (server-scoped: the binary's
  CURRENT, alongside `version`/`source_version`).

Wire: re-expose `INTERNAL_MANIFEST_SCHEMA_VERSION` as `pub` on `db::manifest`;
add `internal_schema_version: u32` to `SnapshotOutput` + `HealthOutput`;
`snapshot_payload` takes the per-graph version (the `Snapshot` does not carry it),
threaded through the embedded CLI + server snapshot callers. `openapi.json`
regenerated (two added int32 properties). Extends the existing healthz / snapshot /
version tests.

* docs(engine): gate internal-schema version at the graph level; record the per-branch read gap

PR reviewers flagged that the open path validates only main's internal-schema stamp, so a branch read could decode a branch stamped outside this binary's range. The stamp is a graph-wide storage-format property (the upgrade path is a whole-graph export/import), so with one binary version every branch is always CURRENT; divergence needs concurrent multi-version writers, an unsupported topology already in one-winner-CAS territory. Gating per-branch would add a second __manifest open per non-main branch read to defend a state we do not support, unearned complexity that regresses the warm-read budget.

Keep the graph-level gate, document it at the code site (refuse_if_internal_schema_unsupported), and record the read-only residual hole as a known gap in invariants.md to close only when multi-version write topologies become supported. Also clarify the sub-floor rebuild message to say "export with the older omnigraph binary that created it."

No behavior change: HEAD already gated at the graph level.

* test(cost): remove the dead commit_graph_reads IO counter

Phase B retired _graph_commits.lance / _graph_commit_actors.lance, so no commit-graph dataset is opened and the commit_graph IOTracker term is structurally always 0. Remove IoCounts::commit_graph_reads, its total_reads() term, the commit_graph IOTracker in OpProbes, and the now-dead commit_graph_wrapper field on QueryIoProbes (it had no accessor — nothing ever attached it). Drop the 7 trivially-true assert_eq!(commit_graph_reads, 0) checks in warm_read_cost.rs and the debug-print refs in write_cost{,_s3}.rs.

Lineage and actor rows now live in __manifest (RFC-013 Phase 7), so the internal_table_scans_are_flat_in_history gate folds into the single manifest_reads flat-assertion — the manifest scan already covers them. Harness-only; no production runtime impact.

* docs: align with the commit-graph retirement + strand storage versioning

Update the always-loaded and user-facing docs to match the landed state: graph lineage lives in __manifest, the _graph_commits.lance / _graph_commit_actors.lance tables are retired, and storage is strict-single-version (no in-place migration — a sub-CURRENT graph is refused with an export/import rebuild).

Fixed stale claims in invariants.md (the migration/atomicity known-gap entry, the Truth Matrix branch-delete row, the read-path/optimize internal-table scope), lance.md (the migrate_v1_to_v2 PK bullet now reflects init-time set; removed the two deleted v3->v4 migration surface guards), testing.md (dropped the deleted migration failpoint tests; manifest-only internal-table term), writes.md (rewrote the Migration-code section to the strand model), storage.md / maintenance.md / constants.md (retired tables out of the layout, internal-table compaction scope, and the constants cheat-sheet), and AGENTS.md. Marked the retirement DONE in the RFC-013 handoff/roadmap and banner-noted the historical RFC analysis.

Added docs/user/operations/upgrade.md (the export/import rebuild recipe) and docs/dev/versioning.md (the four-axis compatibility policy: release lockstep / wire additive / storage strict-single-version / Lance pinned), cross-linked from the audience indexes and the AGENTS.md topic map, and rewrote the in-progress v0.8.0 release note for the strand model + version surfacing. check-agents-md.sh passes (65 links, 62 docs).

* test(manifest): cover the v3-refusal→export/import rebuild cycle and branch stamp inheritance

Two coverage additions from PR review (P1):

(a) sub_current_graph_is_refused_then_rebuilt_via_export_import — the full operator narrative in one flow: load → export → a sub-CURRENT graph (stamp rewound below CURRENT) is refused with the export nudge → fresh init + load(export) → data present and the rebuilt graph opens. The refusal is stamp-only (read before any data), so a stamp-rewound graph is a faithful stand-in for a real older-release graph without a second binary; vector/blob fidelity stays covered by tests/export.rs.

(b) branch_inherits_main_internal_schema_stamp — proves a branch cannot diverge from main's stamp under single-binary operation (create_branch forks main's __manifest, the publisher does not re-stamp), which is why the graph-level (main-only) stamp gate is sufficient for supported inputs. A divergent branch stamp needs concurrent multi-version writers, the unsupported topology recorded as a known gap.
2026-06-28 16:49:49 +02:00

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# Constants & Tunables (cheat sheet)
| Name | Value | Area |
|---|---|---|
| `MANIFEST_DIR` | `__manifest` | manifest layout |
| Commit graph dirs (retired) | `_graph_commits.lance` / `_graph_commit_actors.lance` | retired in Phase B; lineage lives in `__manifest` (`graph_commit` / `graph_head` rows) since RFC-013 Phase 7. A graph this binary creates has neither. |
| Recovery audit dir | `_graph_commit_recoveries.lance` | one row per crash-recovery action (`omnigraph commit list --filter actor=omnigraph:recovery`) |
| Run branch prefix (legacy, removed) | `__run__` | pre-v0.4.0 Run state machine; no longer a reserved name. A graph still carrying `__run__*` branches is sub-v4 and refused on open (rebuild via export/import). |
| Schema apply lock | `__schema_apply_lock__` | schema apply |
| Manifest publisher retry budget | `PUBLISHER_RETRY_BUDGET = 5` | manifest publish |
| Internal manifest schema version | `INTERNAL_MANIFEST_SCHEMA_VERSION = 4` | manifest migrations (v4 = graph lineage in `__manifest`, RFC-013 Phase 7) |
| Merge stage batch | `MERGE_STAGE_BATCH_ROWS = 8192` | merge execution |
| Maintenance concurrency | `OMNIGRAPH_MAINTENANCE_CONCURRENCY=8` | optimize/cleanup |
| Lance blob compaction support | `LANCE_SUPPORTS_BLOB_COMPACTION = false` | optimize |
| Graph index cache size | `8` (LRU) | runtime cache |
| Expand indexed-path frontier ceiling | `OMNIGRAPH_EXPAND_INDEXED_MAX_FRONTIER=1024` | traversal |
| Expand indexed-path hop ceiling | `OMNIGRAPH_EXPAND_INDEXED_MAX_HOPS=6` | traversal |
| Expand CSR-build cost factor | `CSR_BUILD_FACTOR = 1.5` | traversal |
| Expand mode override | `OMNIGRAPH_TRAVERSAL_MODE` (`indexed`\|`csr`; unset = cost-based auto) | traversal |
| Default body limit | `1 MB` | HTTP server |
| Load (bulk-write) body limit | `32 MB` | HTTP server (`/load`; shared by the deprecated `/ingest` alias) |
| Default embed provider/model | `openai-compatible` / `openai/text-embedding-3-large` | engine embedding |
| OpenAI-direct embed model | `text-embedding-3-large` | engine embedding |
| Gemini-direct embed model | `gemini-embedding-2` | engine embedding |
| Embed deadline | `OMNIGRAPH_EMBED_DEADLINE_MS=60000` | engine embedding |
| Embed timeout | `OMNIGRAPH_EMBED_TIMEOUT_MS=30000` | engine embedding |
| Embed retries | `OMNIGRAPH_EMBED_RETRY_ATTEMPTS=4` | engine embedding |
| Embed retry backoff | `OMNIGRAPH_EMBED_RETRY_BACKOFF_MS=200` | engine embedding |
| LANCE memory pool default | `1 GB` (raised in v0.3.0) | runtime |
**Expand traversal dispatch.** With `OMNIGRAPH_TRAVERSAL_MODE` unset, the engine
chooses the indexed (per-hop BTREE) vs CSR (whole-graph in-memory) path with a
cost model over cheap manifest counts (frontier size, |E|, source-vertex count,
hops) plus the index-coverage signal: the indexed path is preferred when its
frontier-relative work beats building the CSR (≈ when `hops × frontier` is a
small fraction of the source-vertex set), and CSR is preferred for dense/deep
traversals or when the BTREE coverage is degraded and a full scan would be paid
per hop. The two ceilings bound the **initial dispatch** frontier/hops (beyond
them CSR is always used); they are not a hard per-hop bound — the cost model
*estimates* total indexed work as ~`hops × frontier × fanout`, so dense fan-out is
priced toward CSR rather than capped mid-traversal. The override flag forces a path (the `auto` result is identical either way;
only the path differs).