The incremental importer was measured at 24.72 min wall / 186s user time for
rockyou (14.3M rows), and Postgres logs showed checkpoints firing every ~22s
due to WAL pressure from random-order B-tree maintenance and full-page-write
amplification. bulkImport.ts (`npm run import:bulk`) avoids all of that:
- Loads raw rows via COPY into a TEMP staging table (no WAL, no index).
- Merges with the existing table's contents into a fresh, unindexed shadow
table via one INSERT ... SELECT ... GROUP BY.
- Adds the primary key and prefix index only after the table is populated,
so Postgres builds them via a single sorted bulk pass instead of 14M
random-order incremental inserts.
- Swaps the shadow table into place at the end.
- The entire run is one transaction: since pwned_passwords_new doesn't exist
outside that transaction, Postgres skips WAL-logging its data entirely,
and any failure rolls back to the exact starting state instead of leaving
a half-migrated table.
- Wordlist hashing runs across a worker_threads pool (--jobs, shared
resolveWorkerUrl helper with the incremental importer's hashWorker) instead
of blocking the single thread that also drives the COPY stream.
- Each phase (hash+copy, merge, reindex, swap) reports its own wall time.
Net effect measured against the same rockyou file/DB: 42 min -> 24.72 min
(fsync fix) -> ~7.3 min (WAL-skip transaction) -> 186.17s (parallel hashing).
