Front-Ends (CLI / HTTP)

The bin/ directory contains the user-facing entry points. Both binaries embed the same Database type, so they demonstrate how the core engine can power different UIs.

Binary	Purpose
`client.rs`	Interactive CLI (REPL) that reads SQL, executes it, and prints tabular output.
`server.rs`	HTTP + JSON API for integration tests or web UIs.

CLI (`bin/client.rs`)

Uses rustyline to provide history, multi-line editing, and familiar shell shortcuts.
Each command calls database.run(sql) and formats the resulting Vec<Tuple>.
Supports meta commands (e.g., .tables) that expose catalog metadata—great for teaching how logical objects map to physical handles.

HTTP (`bin/server.rs`)

Built with axum/hyper (depending on the current Cargo.toml), exposing endpoints such as:
- POST /query – run arbitrary SQL and return rows or an error payload.
- Health/metrics endpoints—which you can extend in labs to surface background worker status or buffer metrics.
Configuration comes from QUILL_DB_FILE, QUILL_HTTP_ADDR, PORT, etc., mirroring how production services inject settings.

Teaching Ideas

Extend the CLI with \describe table to practice catalog lookups.
Add transaction endpoints (BEGIN/COMMIT) to the HTTP server to demonstrate how SessionContext scopes transactions per connection.
Combine CLI interaction with RUST_LOG tracing to walk through the entire query lifecycle.