Handoff doc + CLAUDE.md refresh for next session
- New docs/handoff/20260507-handoff-1.md captures session state, what's implemented, what's pending (ranked recommendations for next moves), sharp edges, and a smoke-test sequence. - CLAUDE.md updated to reflect current reality: ADRs 0008- 0014 added to the decisions-at-a-glance list, the "repository layout (planned)" placeholder replaced with the actual layout, key invariants spelled out, deferred list rebuilt from current requirements.md.
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# Session handoff — 2026-05-07 (1)
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This is the first handover note from the project. The session
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took the project from an empty repository through five
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feature-bearing iterations to a working DSL playground for
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relational database concepts. The next session should be able
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to pick up cleanly from `CLAUDE.md` + this file + the linked
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ADRs.
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## State at handoff
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**Branch:** `main`. Working tree clean. Six commits on top of an
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empty starting tree:
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```
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305e508 INSERT/UPDATE/DELETE + value model + auto-show, with polish
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1650682 Foreign-key relationships, rebuild-table, polish round
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c1e5292 DSL parser, async DB worker, types, history, metadata, polish
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25a0f12 TUI walking skeleton (Phase 4)
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aebfc7d Add Phase 1 requirements checklist with NFRs
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3a0c03d Initial planning docs: CLAUDE.md and ADRs 0000-0008
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```
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**Tests:** 200 passing (183 lib + 17 integration), 0 skipped.
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**Clippy:** clean with `nursery` lints enabled.
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**Release build:** ~5MB single binary.
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The user's terminal is a real TTY; the TUI runs cleanly there
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but cannot be exercised from a non-TTY environment. Use the
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`cargo test` tiers for confident automated checks (Tier 4 PTY
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tests are configured per ADR-0008 but not yet wired with
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`expectrl`).
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## What's implemented
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**TUI shell:**
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- Three-region layout: items list (left), output + input + hint
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(right), bottom status bar with mode-aware shortcuts.
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- Light/dark themes with `--theme` CLI flag and `COLORFGBG`
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auto-detect.
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- Simple/Advanced input modes; `:` one-shot escape with prompt
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reaction (border colour + label flip); auto-inserted space
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after a leading `:` in simple mode.
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- In-line cursor editing (Left/Right/Home/End/Delete/Backspace,
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UTF-8 boundary aware).
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- In-memory command history (Up/Down with draft preservation,
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consecutive-duplicate dedup).
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- PageUp/PageDown output scrolling, wrap-aware (renderer
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reports both visible-row count and total wrapped-row count
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to App).
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**Database (in-memory only this iteration; track 2 brings file
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backing):**
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- SQLite via `rusqlite` 0.39 with `STRICT` tables and
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`PRAGMA foreign_keys = ON`.
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- Dedicated worker thread (ADR-0010): `mpsc::Sender<Request>`
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in / per-request `oneshot` reply out. App holds a
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`Database` handle (cheap to clone).
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- Internal metadata tables (ADR-0012, ADR-0013):
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- `__rdbms_playground_columns(table_name, column_name,
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user_type)` for round-tripping user-facing column types.
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- `__rdbms_playground_relationships(name, parent_table,
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parent_column, child_table, child_column, on_delete,
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on_update)` for named FKs.
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- Internal-table convention: prefix `__rdbms_*`; filtered out
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of `list_tables`. Future internal tables follow this rule.
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- DDL: `create_table`, `add_column`, `drop_table`,
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`add_relationship`, `drop_relationship`, `query_data`,
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`insert`, `update`, `delete`.
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- `rebuild_table` primitive following SQLite's
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ALTER-via-rebuild recipe (ADR-0013): `PRAGMA foreign_keys =
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OFF` outside tx, copy-by-name, `foreign_key_check` before
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commit, atomic metadata updates. Reusable for B2's pending
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column-drop/rename/type-change work.
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- FK error enrichment lists both outbound (INSERT/UPDATE
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relevance) and inbound (DELETE/UPDATE on parent relevance)
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relationships from the metadata.
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**DSL grammar (chumsky):**
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- `create table <Name> with pk [<name>:<type>[,<name>:<type>...]]`
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— single PK or compound; `with pk` alone defaults to
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`id:serial`; bare `create table X` errors with friendly
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hint.
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- `add column [to table] <Name>: <ColName> (<type>)` — `to
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table` optional (just verbose).
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- `drop table <Name>` — refuses if other tables still
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reference this one (lists the offending relationships).
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- `add 1:n relationship [as <name>] from <P>.<col> to
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<C>.<col> [on delete <action>] [on update <action>]
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[--create-fk]` — auto-name format
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`<Parent>_<pcol>_to_<Child>_<ccol>`. `[as <name>]` requires
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the `as` keyword to be unambiguous.
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- `drop relationship <name>` or `drop relationship from
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<P>.<col> to <C>.<col>`.
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- `show table <Name>` — re-renders structure.
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- `show data <Name>` — renders data view.
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- `insert into <T> [(cols)] values (vals)` and
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`insert into <T> (vals)` (short form omitting `values`,
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disambiguated by literal-vs-identifier content).
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- `update <T> set <c>=<v>[,<c>=<v>...] where <c>=<v> | --all-rows`.
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- `delete from <T> where <c>=<v> | --all-rows`.
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App-level commands (always available in both modes per
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ADR-0003): `quit`/`q`, `mode simple|advanced`. The rest of the
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canonical list (`save`, `load`, `export`, etc.) lands with the
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features they belong to.
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**Type system (ADR-0005):**
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All ten user-facing types implemented:
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`text` / `int` / `real` / `decimal` / `bool` / `date` /
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`datetime` / `blob` / `serial` / `shortid`.
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- `serial` → `INTEGER PRIMARY KEY`, auto-filled by SQLite.
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- `shortid` → `TEXT`, auto-generated by us (10-char base58,
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no ambiguous glyphs); explicit values validated against the
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same alphabet/length range.
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- `decimal` / `date` / `datetime` stored as TEXT; per-type
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format validation at INSERT/UPDATE time with friendly
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errors naming the column.
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- `Type::fk_target_type()` (ADR-0011): `serial → int`,
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`shortid → text`, others identity. Used at FK declaration
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to validate the FK column type.
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**Auto-show after writes:** INSERT/UPDATE/DELETE return typed
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result structs (`InsertResult`, `UpdateResult`, `DeleteResult`).
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INSERT auto-shows the just-inserted row (via
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`last_insert_rowid`). UPDATE captures matching rowids up-front
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so the post-update display still finds the rows even if WHERE
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column changed. DELETE reports per-relationship cascade effects
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via row-count diffing of inbound child tables. UPDATE-side
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cascades are not detected (would need value diffing).
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## ADR index (read these before touching the related areas)
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```
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0000 Record architecture decisions (process)
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0001 Language and TUI framework (Rust + Ratatui)
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0002 Database engine (SQLite STRICT)
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0003 Input modes and command dispatch
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0004 Project file format (deferred — track 2)
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0005 Column type vocabulary (ten types)
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0006 Undo snapshots and replay log (deferred)
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0007 Sharing and export (deferred — depends on track 2)
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0008 Testing approach (four tiers)
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0009 DSL command syntax conventions
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0010 Database access via worker thread
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0011 FK column type compatibility
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0012 Internal metadata for user-facing column types
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0013 Relationships, naming, and rebuild-table strategy
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0014 Data operations, value literals, and auto-show
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```
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## What's pending — proposed next moves (in order of my recommendation)
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Several natural directions; ranking is my read at handoff.
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### 1. Project storage — track 2 (highest user impact)
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The largest UX friction left: every quit loses everything. The
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ADR-0004 design is fully in place — `project.yaml` + `data/<table>.csv`
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+ `history.log`, with `playground.db` as a derived artifact.
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What's needed:
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- File-backed projects: `Database::open(path)` already accepts
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any path (currently always `:memory:` from runtime).
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- Auto-temp project on startup, stored in
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`~/.rdbms-playground/projects/temp-<name>` (P1).
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- `save` / `save as` (P2).
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- Auto-save on every change (P3).
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- `load` picker (P4).
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- `playground.db` rebuild from `project.yaml` + `data/`
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(P5) — confirmation when `.db` exists.
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- YAML schema serialiser/deserialiser. The metadata tables
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(ADR-0012, ADR-0013) are already the source of truth.
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- CSV per-table data round-trip.
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- Persistent command history (the in-memory I2 becomes
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durable).
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- `.gitignore` template (F2) and the format-version
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migration framework (F3).
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- The `export`/`import` app-level commands (E1, ADR-0007).
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Estimated scope: substantial — 800–1500 lines + tests +
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ADR(s). Probably wants its own design ADR before coding.
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### 2. Complex WHERE expressions (C5a)
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The user explicitly flagged this as the bridge between DSL
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fluency and real SQL. AND/OR/comparison operators (`<`, `>`,
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`!=`)/`LIKE`/`IS NULL` in UPDATE/DELETE/show-data filters.
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Builds on the existing parser. Requires its own ADR for the
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expression grammar.
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Estimated scope: moderate — 400–600 lines + tests + ADR.
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### 3. Indexes (C3 partial) + EXPLAIN QUERY PLAN rendering (QA1)
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Indexes are conceptually simple but unlock the most powerful
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teaching demo we haven't done yet: showing how `EXPLAIN QUERY
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PLAN` output changes when an index is added. ADR-0008 plus the
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SQLite EXPLAIN docs are the relevant references.
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Estimated scope: moderate — 300–500 lines + tests + ADR.
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### 4. B2 column drops/renames/type changes
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The `rebuild_table` primitive already exists (ADR-0013). What's
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needed is grammar (`drop column from T: c`, `rename column on
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T: old to new`, `change column on T: c (new_type)`) and the
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executor wiring.
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Estimated scope: moderate — 400 lines + tests.
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### 5. Friendly error layer (H1)
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Promote `DbError::friendly_message()` from passthrough to a
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real translator: rewrite SQLite's terse messages to learner-
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friendly ones, identify exact violating columns/rows, suggest
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fixes ("did you mean…").
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Pairs nicely with H1a (parse-error syntax-help that points at
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missing keywords/clauses).
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Estimated scope: moderate — 300–500 lines + tests + ADR.
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### 6. Session log + Markdown export (V4 — the bigger UX project)
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The output panel as a scrollable per-session journal with
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inline rich rendering (smart table-vs-vertical decision based
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on dimensions); Markdown export of the log. Largest single
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piece of UX work outstanding.
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Estimated scope: large — 800+ lines + tests + ADR.
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### 7. m:n convenience command (C4)
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Auto-generates a junction table from `create m:n relationship
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from <T1> to <T2>`; pulls primary keys; assigns a compound PK
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on the junction. Depends on relationships being solid (they
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are).
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Estimated scope: small/moderate once the design is settled —
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200–400 lines + tests + ADR.
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### 8. Smaller polish
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- Readline shortcuts I1b (Ctrl-A/Ctrl-E and friends).
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- Multi-line input I1 (Enter inserts newline, Ctrl-Enter
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submits).
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- Tab completion I3.
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- Syntax highlighting I4.
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- CI (TT5) — the test infrastructure exists; the workflow
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file does not.
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## Sharp edges and subtleties
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Things that took thought during this session and might trip up
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a new agent:
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- **`update()` is pure-sync; the runtime is async.** The Elm
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pattern (ADR-0001 / ADR-0010) is a hard rule. Don't make
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`update()` async or do DB calls inside it; emit `Action`s
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and let the runtime dispatch.
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- **Schema mutations always update metadata.** Both
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`__rdbms_playground_columns` and `__rdbms_playground_relationships`
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are in transactions with the DDL they belong to. A new DDL
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operation that touches columns or relationships and forgets
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to update metadata will produce subtly wrong `describe_table`
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output later.
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- **`rebuild_table` is the load-bearing primitive for any FK
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change.** SQLite cannot ALTER FK constraints in place. The
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primitive runs `PRAGMA foreign_keys = OFF` *outside* a
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transaction (the pragma is a no-op inside one), then
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performs the swap.
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- **Wrap-aware scroll math.** The renderer reports both
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visible-row count and total wrapped-row count to App via
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`note_output_viewport`. Writing scroll-related code without
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understanding this will produce off-by-many bugs (the user
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hit one twice in this session).
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- **Command::target_table vs display_subject.** They differ
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for relationship commands: `target_table()` is the parent
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(drives the post-action description); `display_subject()`
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prints the `from .. to ..` form for the `[ok]` line.
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- **Ratatui's `Paragraph::line_count` is unstable.** We
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approximate via character-count division
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(`approximate_wrapped_rows_from_output` in `ui.rs`). Off-by-
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one at boundaries is acceptable for scroll capping.
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- **`set_default` is not implemented.** ADR-0014 commits to
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the four other actions (`no action`, `restrict`, `set null`,
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`cascade`). When DEFAULT constraints land (C3 partial),
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`set default` joins the family.
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- **The user has expressed strong preferences several times.**
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Reread the relevant ADRs (especially 0009 on syntax
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conventions; 0011 on type compatibility; 0013 on
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relationship naming) before making any DSL grammar change.
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## How to take over
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1. Read this file.
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2. Read `CLAUDE.md` for the working-style rules and current
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layout.
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3. Read `docs/requirements.md` for granular progress.
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4. Skim `docs/adr/README.md`; read any ADR you'll touch.
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5. Run `cargo test` to confirm the 200-test green baseline.
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6. `cargo run --release` to see the app in action — try the
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smoke test below.
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### End-to-end smoke test
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Verifies the playground works from create-table through
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relationships through writes through cascade:
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```
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create table Customers with pk id:serial
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add column Customers: Name (text)
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create table Orders with pk id:serial
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add column Orders: CustId (int)
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add 1:n relationship from Customers.id to Orders.CustId on delete cascade
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insert into Customers ('Alice')
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insert into Customers ('Bob')
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insert into Orders (CustId) values (1)
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show data Customers
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show data Orders
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delete from Customers where id=1
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show data Orders -- empty (cascaded)
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quit
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```
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If anything in that sequence fails, something is wrong. The
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sequence exercises auto-PK, auto-shortid (no, wait — Customers
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is serial, not shortid; for shortid replace `pk id:serial`
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with `pk id:shortid`), FK compatibility (Customers.id is
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serial → Orders.CustId must be int), the rebuild-table dance
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when adding the relationship, the insert short form, and
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cascade delete.
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Reference in New Issue
Block a user