MigrationLedger over the package-owned pg Pool: ensure() creates the
schema_migrations table (version text PRIMARY KEY, applied_at timestamptz
NOT NULL DEFAULT now()) with idempotent DDL; record() inserts an applied
migration with a parameterized, idempotent statement (ON CONFLICT DO
NOTHING — a rerun never double-applies); has()/applied() read the ledger
back in apply order. Re-exported from the driver boundary (src/index.ts)
so no other package needs the pg driver to touch migration state.
implementer
7f6450410e