Module db 

SQLite connection management, WAL setup, and schema migrations.

This module handles the low-level database lifecycle:

• Opening a connection with the right pragmas for performance and safety.
• Running schema migrations on first open or version upgrade.
• Providing separate read-only connections for the query layer.

WAL mode

WAL (Write-Ahead Logging) is enabled on every connection. This gives:

• Concurrent readers while the background writer is writing.
• Better write throughput for the batch write pattern.
• Crash safety — no corruption on unclean shutdown.

Thread safety

rusqlite::Connection is !Send. The writer owns its connection on a dedicated OS thread. Query commands open their own read-only connections.

Functions

open_connection

Open a SQLite connection with WAL mode and performance pragmas.

run_migrations

Run schema migrations to bring the database up to the current version.