omnigraph/docs/releases/v0.4.1.md

# Omnigraph v0.4.1

Omnigraph v0.4.1 closes the multi-statement-mutation atomicity gap that
v0.4.0 documented as a known limitation. Inserts and updates now route
through an in-memory `MutationStaging` accumulator and commit via Lance's
two-phase distributed-write API at end-of-query. A failed mid-query op
no longer leaves Lance HEAD drifted on the touched table — the next
mutation proceeds normally.

## Highlights

- **Staged-write rewire (MR-794)**: `mutate_as` and `load` (Append /
  Merge modes) accumulate insert/update batches into
  `MutationStaging.pending` per touched table. No Lance HEAD advance
  happens during op execution; one `stage_*` + `commit_staged` per
  table runs at end-of-query, then `ManifestBatchPublisher::publish`
  commits the manifest atomically. **For op-execution failures**
  (validation errors, missing endpoints, parse-time D₂ rejection), Lance
  HEAD on every staged table is untouched and the next mutation
  proceeds normally. A narrowed residual remains at the
  finalize→publisher boundary (multi-table `commit_staged` is not
  atomic with the manifest commit) — see [docs/runs.md](../runs.md)
  "Finalize → publisher residual" for details.
- **D₂ parse-time rule**: a single mutation query is either
  insert/update-only or delete-only. Mixed → rejected with a clear
  error directing the caller to split into two queries. Lance 4.0.0
  has no public two-phase delete; deletes still inline-commit, and D₂
  keeps that path safe.
- **Read-your-writes via DataFusion `MemTable`**: read sites in
  multi-statement mutations consume `TableStore::scan_with_pending`,
  which Lance-scans the committed snapshot at the captured
  `expected_version` and unions with a DataFusion `MemTable` over the
  pending batches. Replaces the previous "reopen at staged Lance
  version" pattern.
- **Coordinator swap-restore eliminated** from `mutate_with_current_actor`.
  Branch is threaded explicitly through the per-op execution path
  (`execute_named_mutation`, `execute_insert`, `execute_update`,
  `execute_delete*`, `validate_edge_insert_endpoints`,
  `ensure_node_id_exists`). The `swap_coordinator_for_branch` /
  `restore_coordinator` API and `CoordinatorRestoreGuard` are removed
  from `mutation.rs`. (`merge.rs` keeps its own swap pattern; that's
  a separate workflow tracked in MR-793.)
- **`docs/invariants.md` §VI.25** flips from `aspirational/open` to
  `upheld for inserts/updates`. The within-query read-your-writes
  guarantee is now load-bearing for the publisher CAS contract.

## Behavior changes

- A failed multi-statement mutation no longer surfaces
  `ExpectedVersionMismatch` on the *next* mutation against the same
  table. The next call proceeds normally — Lance HEAD on staged
  tables is unchanged.
- Mixed insert/update + delete in one query is rejected at parse
  time. Existing test queries that mixed both must be split.
- `MutationStaging`'s shape changed: `pending: HashMap<String, PendingTable>`
  + `inline_committed: HashMap<String, SubTableUpdate>` replaces the
  previous `latest: HashMap<String, StagedTable>`. This is an internal
  type; no public API impact.

## Residual / out of scope

- **`LoadMode::Overwrite`** keeps the legacy inline-commit path
  (truncate-then-append doesn't fit the staged shape). A mid-overwrite
  failure can still drift Lance HEAD on a partially-truncated table;
  the next overwrite replaces it. Operator-driven, rare.
- **Delete-only multi-statement mutations** still inline-commit per op.
  D₂ keeps inserts/updates from coexisting with deletes, so the
  inline path remains atomic per op but not per query for delete-only
  cascades. Closing this requires Lance to expose
  `DeleteJob::execute_uncommitted`; tracked in MR-793 / Lance-upstream.
- **`schema_apply`, `branch_merge_internal`, `ensure_indices`** still
  use Lance's inline-commit APIs. The two-phase pattern is in
  `mutate_as` and `load` only; hoisting it to a storage-trait
  invariant covering all writers is MR-793.

## Tests added

- `tests/runs.rs::partial_failure_leaves_target_queryable_and_unblocks_next_mutation`
  (replaces the old `partial_failure_observably_rolls_back_but_blocks_next_mutation_on_same_table`)
- `tests/runs.rs::mutation_rejects_mixed_insert_and_delete_at_parse_time`
- `tests/runs.rs::mixed_insert_and_update_on_same_person_coalesces_to_one_merge`
- `tests/runs.rs::multiple_appends_to_same_edge_coalesce_to_one_append`
- `tests/runs.rs::multi_statement_inserts_publish_exactly_once`
- `tests/runs.rs::load_with_bad_edge_reference_unblocks_next_load`
- `tests/runs.rs::load_with_cardinality_violation_unblocks_next_load`

## Files changed

- `crates/omnigraph/src/exec/staging.rs` (NEW) — `MutationStaging`,
  `PendingTable`, `PendingMode`, `StagedTablePath`,
  `dedupe_merge_batches_by_id`.
- `crates/omnigraph/src/exec/mutation.rs` — D₂ check; per-op
  rewires (`execute_insert`, `execute_update`, `execute_delete*`);
  branch threading; coordinator-swap removal; helper
  `validate_edge_cardinality_with_pending`; helper
  `concat_match_batches_to_schema`; `apply_assignments` updated to
  copy unassigned blob columns from full-schema scans.
- `crates/omnigraph/src/loader/mod.rs` — `load_jsonl_reader` split:
  staged path for Append/Merge, legacy inline-commit path for
  Overwrite. Helpers `collect_node_ids_with_pending` and
  `validate_edge_cardinality_with_pending_loader`.
- `crates/omnigraph/src/table_store.rs` — `scan_with_pending`,
  `count_rows_with_pending` (DataFusion `MemTable`-backed union with
  Lance scan).
- `Cargo.toml` (workspace) + `crates/omnigraph/Cargo.toml` — added
  `datafusion = "52"` direct dep (transitively pulled by Lance
  already; required for `MemTable`).
- `docs/runs.md` — removed "Known limitation" section; documented
  the new accumulator + D₂ + LoadMode::Overwrite residual.
- `docs/invariants.md` — §VI.25 status flipped to `upheld for
  inserts/updates`.
- `docs/architecture.md` — added "Mutation atomicity — in-memory
  accumulator (MR-794)" subsection; refreshed the engine + state
  diagrams to drop `RunRegistry` and add `MutationStaging`.
- `docs/execution.md` — rewrote the mutation flow sequence diagram
  for the staged-write path; updated the `LoadMode` table to call
  out per-mode commit semantics; rewrote `load` vs `ingest`.
- `docs/query-language.md` — documented the D₂ parse-time rule.
- `docs/errors.md` — added the D₂ `BadRequest` rejection path.
- `docs/storage.md` — dropped the live `_graph_runs.lance` reference
  (legacy from MR-771) from the layout diagram and prose.
- `docs/branches-commits.md` — moved `__run__<id>` to a legacy note;
  removed `publish_run` from the publish-trigger list.
- `docs/audit.md` — current `_as` API list refreshed; legacy
  `RunRecord.actor_id` moved to a historical note.
- `docs/constants.md` — marked the run registry / branch-prefix rows
  as legacy.
- `docs/cli.md` — replaced the legacy `omnigraph run *` quickstart
  block with `omnigraph commit list/show`.
- `docs/testing.md` — extended the `runs.rs` row to cover the new
  MR-794 contract tests; added the `staged_writes.rs` row.
- `AGENTS.md` (CLAUDE.md symlink) — updated the atomic-per-query
  description and the L2 capability matrix row.

## Included Changes

- MR-794 step 2+ — rewire `mutate_as` and `load` via in-memory
  `MutationStaging` + `stage_*` / `commit_staged` per touched table at
  end-of-query.
- (MR-794 step 1 shipped in v0.4.0's PR #67 — `StagedWrite`,
  `stage_append`, `stage_merge_insert`, `commit_staged`,
  `scan_with_staged`, `count_rows_with_staged` — and is the substrate
  this release builds on.)