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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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iteration status
9 done

Iteration 9 — database engine

Format: product/story-iteration-template. Part of Story — one language, one runtime, one database, one binary.

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.

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).