writeonce/docs/stories/language-runtime-database/done/09-database-engine.md
shoney.arickathil ca2ed96e49 docs: story frontmatter + Dataview board views
- 28 story files gain YAML frontmatter: iteration id, status
  (mirrors folder), chain position (7 files, positions 1-6)
- board-views.md: Dataview queries (not-done, by-status lanes,
  chain order, active); Kanban caveat — view only, frontmatter
  is source of truth, folder move + status key change together
- board points at the views

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-08-21 12:17:50 +02:00

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2.9 KiB
Markdown

---
iteration: "9"
status: done
---
# Iteration 9 — database engine
> Format: `product/story-iteration-template`. Part of
> [Story — one language, one runtime, one database, one binary](../00-story.md).
## Goals
- The language's oldest promise executes on the new runtime: every class is
a table. `insert` and `select` stop trapping (`DB_STUB` retires) and run
against class-shaped row storage inside the VM's shards.
- Data survives anything: a typed write-ahead log with ack-after-fsync,
parallel boot replay, and a crash battery proving no committed row is
ever lost and no half-applied transaction ever visible.
## Acceptance Criteria
- What to achieve?
- **Given** a class annotated `@table` and a method inserting rows,
- **when** the method runs,
- **then** the insert is WAL-logged before acknowledgment, visible to
subsequent `select`, and the pricing fixture that previously trapped
`DB_STUB` now passes with real data.
- What to achieve?
- **Given** kill -9 at arbitrary points during committed writes,
- **when** the process reboots and replays,
- **then** every acknowledged commit is present, no unacknowledged
partial write is visible, and replay across shards completes without
manual steps.
- What to achieve?
- **Given** a `@unique` field and a duplicate insert,
- **when** it executes,
- **then** the insert traps with the unique-violation code and
secondary indexes remain consistent (maintained only through the
engine's row choke points).
## Out Of Scope
- Cypher/document query paradigms and `LIVE` subscriptions (the query
layer's later phases; `prototypes/wo-db` stays the reference).
- Cross-shard 2PC transactions; Postgres mirroring (exists on the Rust
side; ports after parity).
## Info
- Doctrine: RAM is authoritative; the WAL makes it durable; indexes drift
unless writes go through the row API — the Rust runtime learned this
lesson, the C engine enforces it.
- The wo-db overlap manifest keeps the C++ prototype and this engine
answer-compatible where features overlap.
- **Ownership/GC analysis (2026-08-15):** the engine and the VM heap are two
memory worlds crossed only by copy — rows store no VM pointers, GC-managed
values in stored fields are a compile error, and everything a query returns
is copied out — so the collector never traces rows and the engine never
counts references. The full analysis (row views as borrows without a
runtime net, cursor stability, GC-pause interaction) lives in the 9b
design's section 6:
[`2026-08-15-table-relations-query-design.md`](../../../superpowers/specs/2026-08-15-table-relations-query-design.md).
## Proposed Solution
- Execute the existing plan: `docs/superpowers/plans/2026-08-01-db-engine-binding.md`
(class-shaped row slabs with a choke-point row API, typed WAL + parallel
replay + crash battery, insert execution, doctrine-enforced indexes +
`@unique` trap, select subset, db corpus).