Run once

By default (runOnce: true) each seeder is tracked in a seeders table — similar to how TypeORM tracks migrations. On the next boot — including watch-mode restarts — seeders already recorded in that table are skipped.

In combination with dropSchema

When TypeORM's dropSchema: true is set, the entire schema — including the seeders table — is dropped on every start, so all seeders run regardless of runOnce.

dropSchema	runOnce	What happens
true	true	Tracking table dropped → all seeders run (fresh schema needs fresh seeds)
true	false	Always runs
false	true	Tracking table persists → already-run seeders are skipped
false	false	Always runs (tracking disabled)

dropSchema: true is typical in development when you want a clean slate on every restart — seeding every run is exactly what you want in that scenario. runOnce: true with a persistent schema is the right default for staging and production, where duplicate data is the concern.

Evolving seed data

Treat seeders the way you treat migrations: once a seeder has run in a persistent environment, consider it immutable. If you need more data or different data, create a new seeder class rather than editing the existing one:

@Seeder()
class UserSeeder implements SeederInterface { ... }      // already ran, leave it alone

@Seeder({ dependencies: [UserSeeder] })
class UserSeederV2 implements SeederInterface { ... }   // adds more users on next boot

This keeps the history table accurate and avoids the question of what re-running a seeder would mean for data that already exists. This applies to environments where dropSchema: false and runOnce: true — in development with dropSchema: true, the schema is wiped on every restart anyway.

Re-seeding

To force a seeder to run again, use seed:untrack:

npm

npx @joakimbugge/typeorm-seeder seed:untrack UserSeeder -d ./dist/datasource.js

yarn

yarn @joakimbugge/typeorm-seeder seed:untrack UserSeeder -d ./dist/datasource.js

pnpm

pnpm exec @joakimbugge/typeorm-seeder seed:untrack UserSeeder -d ./dist/datasource.js

Or delete its row directly from the seeders table:

DELETE FROM "seeders" WHERE name = 'UserSeeder';

To reset everything and re-run all seeders on next boot:

DELETE FROM "seeders";

INFO

If your factories use random data (e.g. via Faker), setting runOnce: false means you will get a completely different dataset on every restart. This can be useful in some development setups, but is usually not what you want.