writeonce/docs/stories/language-runtime-database/09-database-engine.md

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.

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).