[ruby-on-rails] Reset the database (purge all), then seed a database

Is there a rake command to wipe out the data in the database tables?

How do I create a db:seed script to pre-fill data to my tables?

on Rails 6 you can now do something like

rake db:seed:replant This Truncates tables of each database for current environment and loads the seeds

https://blog.saeloun.com/2019/09/30/rails-6-adds-db-seed-replant-task-and-db-truncate_all.html

$ rails db:seed:replant --trace
** Invoke db:seed:replant (first_time)
** Invoke db:load_config (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute db:load_config
** Invoke db:truncate_all (first_time)
** Invoke db:load_config
** Invoke db:check_protected_environments (first_time)
** Invoke db:load_config
** Execute db:check_protected_environments
** Execute db:truncate_all
** Invoke db:seed (first_time)
** Invoke db:load_config
** Execute db:seed
** Invoke db:abort_if_pending_migrations (first_time)
** Invoke db:load_config
** Execute db:abort_if_pending_migrations
** Execute db:seed:replant

You can use rake db:reset when you want to drop the local database and start fresh with data loaded from db/seeds.rb. This is a useful command when you are still figuring out your schema, and often need to add fields to existing models.

Once the reset command is used it will do the following: Drop the database: rake db:drop Load the schema: rake db:schema:load Seed the data: rake db:seed

But if you want to completely drop your database you can use rake db:drop. Dropping the database will also remove any schema conflicts or bad data. If you want to keep the data you have, be sure to back it up before running this command.

This is a detailed article about the most important rake database commands.

You can delete everything and recreate database + seeds with both:

1. rake db:reset: loads from schema.rb
2. rake db:drop db:create db:migrate db:seed: loads from migrations

Make sure you have no connections to db (rails server, sql client..) or the db won't drop.

schema.rb is a snapshot of the current state of your database generated by:

rake db:schema:dump

As of Rails 5, the rake commandline tool has been aliased as rails so now

rails db:reset instead of rake db:reset

will work just as well

If you don't feel like dropping and recreating the whole shebang just to reload your data, you could use MyModel.destroy_all (or delete_all) in the seed.db file to clean out a table before your MyModel.create!(...) statements load the data. Then, you can redo the db:seed operation over and over. (Obviously, this only affects the tables you've loaded data into, not the rest of them.)

There's a "dirty hack" at https://stackoverflow.com/a/14957893/4553442 to add a "de-seeding" operation similar to migrating up and down...