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- storage.md: document the row-level CAS annotation on `__manifest.object_id` and the `expected_table_versions` OCC contract on `ManifestBatchPublisher::publish`. - errors.md: list `ManifestConflictDetails` and its variants alongside `ManifestError`. - constants.md: add `PUBLISHER_RETRY_BUDGET = 5`. Per AGENTS.md "Maintenance contract": new schema construct, new constant, and new typed error shape all need to ship with the source change.
48 lines
4.1 KiB
Markdown
48 lines
4.1 KiB
Markdown
# Storage
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## L1 — Lance dataset (per node/edge type)
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Every node type and every edge type is its own Lance dataset:
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- **Columnar Arrow storage**: each property is a column; nullable per Arrow schema.
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- **Fragments**: data is partitioned into fragments; new writes create new fragments.
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- **Manifest versioning**: every commit produces a new dataset version; old versions remain readable.
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- **Stable row IDs**: enabled by OmniGraph for the commit-graph and run-registry datasets so durable references survive compaction.
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- **Append / delete / `merge_insert`**: native Lance write modes.
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- **Per-dataset branches** (Lance native): copy-on-write at the dataset level.
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- **Object-store agnostic**: file://, s3://, gs://, az://, http (read-only via Lance) — OmniGraph wires file:// and s3:// (`storage.rs`).
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## L2 — Multi-dataset coordination via `__manifest`
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OmniGraph is **not** a single Lance dataset; it is a *graph* of datasets coordinated through one append-only manifest table.
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- **Manifest table**: `__manifest/` Lance dataset.
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- **Layout** (`db/manifest/layout.rs`, `db/manifest/state.rs`):
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- `nodes/{fnv1a64-hex(type_name)}` — one Lance dataset per node type
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- `edges/{fnv1a64-hex(edge_type_name)}` — one Lance dataset per edge type
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- `__manifest/` — the catalog of all sub-tables and their published versions
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- `_graph_commits.lance` / `_graph_commit_actors.lance` — the commit graph and its actor map
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- `_graph_runs.lance` / `_graph_run_actors.lance` — the run registry and its actor map
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- **Manifest row schema** (`object_id, object_type, location, metadata, base_objects, table_key, table_version, table_branch, row_count`):
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- `object_type` ∈ `table | table_version | table_tombstone`
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- `table_key` ∈ `node:<TypeName> | edge:<EdgeName>`
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- `table_branch` is `null` for the main lineage and the branch name otherwise
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- **Snapshot reconstruction**: latest visible `table_version` per `(table_key, table_branch)` minus tombstones — rows where `object_type = table_tombstone`, whose own `table_version` (acting as the tombstone version) is `>= the entry's table_version`.
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- **Atomic publish**: multi-dataset commits publish via a `ManifestBatchPublisher` so a single write to `__manifest` flips all the new sub-table versions visible at once.
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- **Row-level CAS on the merge-insert join key**: `object_id` carries `lance-schema:unenforced-primary-key=true` so Lance's bloom-filter conflict resolver rejects two concurrent commits that land the same `object_id` row. Without this annotation, Lance's transparent rebase would admit silent duplicates of `version:T@v=N` from racing publishers (see `.context/merge-insert-cas-granularity.md`).
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- **Optimistic concurrency control on publish**: `ManifestBatchPublisher::publish` accepts a `expected_table_versions: HashMap<table_key, u64>` map. Each entry asserts the manifest's current latest non-tombstoned version for that table is exactly what the caller observed; mismatches surface as `OmniError::Manifest` with `ManifestConflictDetails::ExpectedVersionMismatch { table_key, expected, actual }`. Empty map preserves the legacy "best-effort publish" semantics. The publisher uses `conflict_retries(0)` against Lance and owns retry itself (`PUBLISHER_RETRY_BUDGET = 5`), re-running the pre-check on each iteration so concurrent advances surface as `ExpectedVersionMismatch` rather than being silently rebased through.
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## URI scheme support (`storage.rs`)
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| Scheme | Backend | Notes |
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| local path / `file://` | `LocalStorageAdapter` (tokio) | Normalized to absolute paths |
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| `s3://bucket/prefix` | `S3StorageAdapter` (object_store) | Honors `AWS_ENDPOINT_URL_S3`, `AWS_ALLOW_HTTP`, `AWS_S3_FORCE_PATH_STYLE` |
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| `http(s)://host:port` | HTTP client to `omnigraph-server` | Used by CLI as a target, not a storage backend |
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## Object-store env vars (S3-compatible)
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- `AWS_REGION`, `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY`, `AWS_SESSION_TOKEN`
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- `AWS_ENDPOINT_URL`, `AWS_ENDPOINT_URL_S3` — for MinIO / RustFS / GCS-via-XML
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- `AWS_S3_FORCE_PATH_STYLE=true` — path-style URLs
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- `AWS_ALLOW_HTTP=true` — allow plain HTTP (local dev)
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