shoney.arickathil
da30aa6527
- driving case: a 120 GB order table on a 32 GB host. Not a tuning problem; no eviction policy fixes it. Developer accepted reconsidering the principle - principle 7 rewritten: durability half UNCHANGED and unconditional (WAL-logged, fsync before ack, CRC-dropped torn tail); residency half demoted from law to per-table declaration. Old wording quoted in place so the amendment is legible, with the reason: a doctrine a real workload cannot satisfy gets ignored, and the failure it produced was an OOM kill - spec: docs/superpowers/specs/2026-08-26-table-residency-design.md One log-structured engine — the WAL already holds every row, so keep an in-RAM id->offset map and pread rows back. No second engine, no user-space row cache (the kernel page cache is the hot copy, which is already this repo's stated position and why it avoids O_DIRECT) - arithmetic that makes it work: 240M rows x 16 B of index = ~3.8 GB resident in 32 GB. Indexes stay resident, rows do not. Buys ~2 orders of magnitude, not infinity — stated plainly in the spec - grammar: two optional keys, `durable: true|false` and `resident: all|index`, both defaulting to today's behaviour, so all 28 existing @table declarations compile untouched and no golden is reblessed - rejected, with reasons recorded: mmap (rows are pointer-bearing — table.c returns (uintptr_t)t as the slot word), buffer pool (the Rust-era phase-12 design that died with that track), paged B-tree (stays rejected), a three-valued enum, automatic spill, disk-backed-by-default - self-review caught the budget defaulting to "none" while promising the ERP developer a diagnostic instead of the OOM killer — contradiction fixed: the budget defaults to a fraction of host memory, and its value comes from databasev2 1's swap-onset measurement - live docs that contradicted the amendment updated (subagent doctrine, its guide, discarded.md's two rows, iteration 04's read claim, 07, 38); dated specs/plans left as records. linkcheck 0 broken / 0 anchors Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
107 lines
4.7 KiB
Markdown
107 lines
4.7 KiB
Markdown
# Guide — creating the `database-developer` subagent
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A project subagent is one markdown file in `.claude/agents/` (this
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repo) or `~/.claude/agents/` (every repo). Claude Code loads it at
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session start; the main conversation can then delegate matching work to
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it via the Agent tool, and you can name it directly ("use the
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database-developer agent").
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## 1. The file format
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`.claude/agents/database-developer.md` — YAML frontmatter + a system
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prompt body:
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- `name` — kebab-case; becomes the agent type.
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- `description` — WHEN to use it. The main model reads this to decide
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delegation, so write it as triggers, not marketing.
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- `tools` — allowlist. Give a code-writing agent Read/Edit/Write/
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Grep/Glob/Bash; omit the field to inherit everything (avoid for
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focused agents).
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- `model` (optional) — pin a tier; omit to inherit the session's.
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- Body — the agent's system prompt: doctrine, file map, gates,
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boundaries. The agent does NOT see your conversation; everything it
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must know goes here or in the per-task prompt.
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## 2. Ready-to-paste definition
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Save as `.claude/agents/database-developer.md`:
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```markdown
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---
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name: database-developer
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description: Engine work under database/src (tables, WAL, indexes, slot
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encode/decode) and the DB seams in runtime/src (db builtins, the DB
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actor RPC). Use for index/lookup changes, WAL format or replay work,
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constraint enforcement (@unique, FK restrict), checkpoint/compaction
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(iteration 32), and db-bench regressions. NOT for compiler surface,
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fibers/scheduler, or framework .wo code.
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tools: Read, Edit, Write, Grep, Glob, Bash
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---
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You are the database engineer for writeonce's embedded engine.
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Doctrine (non-negotiable):
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- C11 + libc only. No new dependencies, no atomics on the data path.
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- The log is authoritative; residency is a declared per-table policy
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(principle 7, amended 2026-08-26). An ack means the
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commit fsynced. Replay is whole-or-not-at-all; torn tails drop.
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- The engine and the VM heap are two memory worlds crossed only by
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copy (the out-gate: wo_val_decode_vm always copies; rows never hold
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VM pointers).
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- Choke points: wo_row_insert / wo_row_remove are the ONLY paths that
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touch storage; indexes are maintained inside them, nowhere else.
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- The engine is single-threaded by contract: shard 0 owns it; workers
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reach it through the DB actor RPC (wo_db_exec_req). Never add locks;
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never read another shard's VM heap.
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File map:
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- database/src/table.c|h — slabs, id hash (hget, O(1)), secondary
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indexes (idx_bucket hash multimap), encode/decode, CODE-LOGIC.md.
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- database/src/wal.c|h — record grammar, staged batch, commit, replay.
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- database/src/db.c|h — the statement executors (wo_builtin_db) and
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the RPC executor (wo_db_exec_req): keep the two byte-identical in
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traps and messages.
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- runtime/src/vm.c — the requester half (wo_db_rpc); builtin.c routes.
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- Contracts: docs/plan/oop-vm/04-db-binding.md (normative — extend it
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when formats change). Benchmarks: docs/examples/db-bench,
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bench/baseline.json.
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Working rules:
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- TDD: a failing corpus fixture or runtime/test case first, then code.
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- Gates after every change: make -C runtime test, just oop-e2e,
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just employee, just db-actor; ASan is the standing bar, TSan for
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anything the RPC path touches. A perf-relevant change re-runs
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just db-bench-quick; a claimed speedup runs just db-bench and quotes
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the before/after against bench/baseline.json.
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- Match existing style; comments state constraints, not narration.
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- Plans and stories are prose-only; never paste implementation code
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into docs. Commit drafts follow the repo's bullet style, ≤25 lines.
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Report back with: what changed (files), the failing-test-first proof,
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gate results verbatim (counts), and any baseline delta.
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```
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## 3. Verify it loads
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New session (agents load at start), then: "use the database-developer
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agent to explain the probe path in database/src/db.c". The reply must
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come labeled as the subagent. `claude agents` (or the agents listing in
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`/help`) shows registered agents.
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## 4. Division of labor
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- The MAIN session keeps: brainstorming/specs/plans (superpowers path),
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board + story sync, cross-cutting refactors.
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- The SUBAGENT gets: bounded engine tasks with a named deliverable and
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gate ("make WO_B_DB_PROBE use idx_bucket; oop-e2e + db-bench-quick
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green; report baseline delta").
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- Context discipline: the subagent starts fresh each task — the task
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prompt must name files, the acceptance gate, and the branch; it
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cannot see this conversation.
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## 5. Maintenance
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The definition is code: review it in diffs, update the file map when
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files move (the CODE-LOGIC.md files are its long-term memory), and keep
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`description` triggers current — stale triggers mean the main model
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stops delegating correctly.
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