claude@clouddev1
3a0c03d781
Captures up-front design decisions for RDBMS Playground: stack (Rust + Ratatui + SQLite), input modes, project file format, type vocabulary, undo snapshots and replay log, sharing/export, and testing approach. ADR-0000 establishes the ADR practice itself and mandates index upkeep alongside any ADR change.
57 lines
2.0 KiB
Markdown
57 lines
2.0 KiB
Markdown
# ADR-0002: Database engine
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## Status
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Accepted
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## Context
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The application teaches relational database concepts. Requirements
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on the engine:
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- File-based, with a single binary file that can live in the
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project folder.
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- Real RDBMS feature set: typed columns, primary keys, foreign keys
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with referential integrity, indexes, query planner output we can
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expose to learners.
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- Industry adoption — students should leave with a skill that maps
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to something they will encounter again.
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- Embeddable from Rust without arcane build steps.
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Candidates considered:
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- **SQLite** — file-based, near-universal adoption, supports FK
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enforcement, has `EXPLAIN QUERY PLAN`, and since 3.37 supports
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`STRICT` tables which give proper type enforcement instead of
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SQLite's traditional loose type affinity.
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- **DuckDB** — file-based, modern, but analytical/columnar by
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design; would teach analytical instincts that mislead in
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transactional contexts.
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- **Embedded Postgres (pglite, pg_embed)** — closest to a "real"
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RDBMS, but adds friction and complicates packaging.
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## Decision
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Use **SQLite** via the `rusqlite` crate. All tables are created as
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`STRICT` tables. Foreign-key enforcement is enabled per-connection
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(`PRAGMA foreign_keys = ON`).
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Simplified user-facing column types (see ADR-0005) are mapped to
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the underlying SQLite STRICT types at parse time.
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## Consequences
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- Tight, low-friction packaging — `rusqlite` bundles SQLite.
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- `EXPLAIN QUERY PLAN` output is directly usable for the query
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analysis feature (ADR pending).
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- SQLite's `ALTER TABLE` is limited (e.g. type changes, some
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drops). Schema evolution will use the rebuild-table technique
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internally; this is hidden from users in simple mode and exposed
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honestly in advanced mode.
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- STRICT tables forbid the historical permissive typing students
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might encounter elsewhere — this is intentional and matches the
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pedagogical goal.
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- Booleans are stored as `INTEGER` (0/1) per SQLite's STRICT type
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set; the `bool` user-facing type maps to this and is rendered as
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`true`/`false` in result views.
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