Purge or recreate a Ruby on Rails database_问答_开发者

I have a dev Ruby on Rails database full of data. I want to delete everything and rebuild the database. I'm thinking of using something like:

rake db:recreate

Is t开发者_开发百科his possible?

I know two ways to do this:

This will reset your database and reload your current schema with all:

rake db:reset db:migrate

This will destroy your db and then create it and then migrate your current schema:

rake db:drop db:create db:migrate

All data will be lost in both scenarios.

On Rails 4, all needed is

$ rake db:schema:load

That would delete the entire contents on your DB and recreate the schema from your schema.rb file, without having to apply all migrations one by one.

I use the following one liner in Terminal.

$ rake db:drop && rake db:create && rake db:migrate && rake db:schema:dump && rake db:test:prepare

I put this as a shell alias and named it remigrate

By now, you can easily "chain" Rails tasks:

$ rake db:drop db:create db:migrate db:schema:dump db:test:prepare # db:test:prepare no longer available since Rails 4.1.0.rc1+

Update: In Rails 5, this command will be accessible through this command:

rails db:purge db:create db:migrate RAILS_ENV=test

As of the newest rails 4.2 release you can now run:

rake db:purge

Source: commit

# desc "Empty the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:drop:all to drop all databases in the config). Without RAILS_ENV it defaults to purging the development and test databases."
  task :purge => [:load_config] do
    ActiveRecord::Tasks::DatabaseTasks.purge_current
  end

It can be used together like mentioned above:

rake db:purge db:create db:migrate RAILS_ENV=test

Depending on what you're wanting, you can use…

rake db:create

…to build the database from scratch from config/database.yml, or…

rake db:schema:load

…to build the database from scratch from your schema.rb file.

From the command line run

rake db:migrate:reset

In Rails 6 there is a convenient way for resetting DB and planting seeds again:

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

https://weblog.rubyonrails.org/2019/3/15/this-week-in-rails-security-fixes-bulk-insert-and-upsert-seeds-replanting/

Use like

rake db:drop db:create db:migrate db:seed

All in one line. This is faster since the environment doesn't get reloaded again and again.

db:drop - will drop database.

db:create - will create database (host/db/password will be taken from config/database.yml)

db:migrate - will run existing migrations from directory (db/migration/.rb)*.

db:seed - will run seed data possible from directory (db/migration/seed.rb)..

I usually prefer:

rake db:reset

to do all at once.

Cheers!

Just issue the sequence of the steps: drop the database, then re-create it again, migrate data, and if you have seeds, sow the database:

rake db:drop db:create db:migrate db:seed

Since the default environment for rake is development, in case if you see the exception in spec tests, you should re-create db for the test environment as follows:

RAILS_ENV=test rake db:drop db:create db:migrate

In most cases the test database is being sowed during the test procedures, so db:seed task action isn't required to be passed. Otherwise, you shall to prepare the database:

rake db:test:prepare

RAILS_ENV=test rake db:seed

Additionally, to use the recreate task you can add into Rakefile the following code:

namespace :db do
   task :recreate => [ :drop, :create, :migrate ] do
      if ENV[ 'RAILS_ENV' ] !~ /test|cucumber/
         Rake::Task[ 'db:seed' ].invoke
      end
   end
end

Then issue:

rake db:recreate

You can manually do:

rake db:drop
rake db:create
rake db:migrate

Or just rake db:reset, which will run the above steps but will also run your db/seeds.rb file.

An added nuance is that rake db:reset loads directly from your schema.rb file as opposed to running all the migrations files again.

You data gets blown away in all cases.

You can use this following command line:

rake db:drop db:create db:migrate db:seed db:test:clone

To drop a particular database, you can do this on rails console:

$rails console
Loading development environment
1.9.3 > ActiveRecord::Migration.drop_table(:<table_name>)
1.9.3 > exit

And then migrate DB again

$bundle exec rake db:migrate

On rails 4.2, to remove all data but preserve the database

$ bin/rake db:purge && bin/rake db:schema:load

https://github.com/rails/rails/blob/4-2-stable/activerecord/CHANGELOG.md

You can use db:reset - for run db:drop and db:setup or db:migrate:reset - which runs db:drop, db:create and db:migrate.

dependent at you want to use exist schema.rb

According to Rails guide, this one liner should be used because it would load from the schema.rb instead of reloading the migration files one by one:

rake db:reset

Because in development , you will always want to recreate the database,you can define a rake task in your lib/tasks folder like that.

  namespace :db do
      task :all => [:environment, :drop, :create, :migrate] do
   end 
end

and in terminal you will run

rake db:all

it will rebuild your database

3 options, same result:

1. All steps:

  $ rake db:drop           # deletes the database for the current env
  $ rake db:create         # creates the database for the current env
  $ rake db:schema:load    # loads the schema already generated from schema.rb / erases data
  $ rake db:seed           # seed with initial data

2. Reset:

  $ rake db:reset          # drop / schema:load / seed

3. Migrate:reset:

  $ rake db:migrate:reset  # drop / create / migrate
  $ rake db:seed

Notes:

If schema:load is used is faster than doing all migrations, but same result.
All data will be lost.
You can run multiple rakes in one line.
Works with rails 3.

I think the best way to run this command:

**rake db:reset** it does db:drop, db:setup
 rake db:setup does db:create, db:schema:load, db:seed

Simply you can run

rake db:setup

It will drop database, create new database and populate db from seed if you created seed file with some data.

I use:

rails db:drop to delete the databases.
rails db:create to create the databases based on config/database.yml

The previous commands may be replaced with rails db:reset.

Don't forget to run rails db:migrate to run the migrations.

I've today made quite a few changes to my rails schema. I realised I needed an additional two models in a hierarchy and some others to be deleted. There were many little changes required to the models and controllers.

I added the two new models and created them, using:

rake db:migrate

Then I edited the schema.rb file. I manually removed the old models that were no longer required, changed the foreign key field as required and just reordered it a bit to make it clearer to me. I deleted all the migrations, and then re-ran the build via:

rake db:reset

It worked perfectly. All the data has to be reloaded, of course. Rails realised the migrations had been deleted and reset the high-water mark:

-- assume_migrated_upto_version(20121026094813, ["/Users/sean/rails/f4/db/migrate"])

TL;DR - I use this rake script during development to blow away everything, including the schema file, then rebuild directly from migration scripts. It rebuilds both dev and test databases simultaneously. It's the only way I've found to guarantee everything lines up the way I expect. Been using it for years without a problem.

# lib/tasks/db_rebuild.rake

require 'fileutils'

namespace :db do
  desc "Create DB if it doesn't exist, then migrate and seed"
  task :build do
    Rake::Task["db:create"].invoke
    Rake::Task["db:migrate"].invoke
    Rake::Task["db:seed"].invoke
  end

  desc "Drop database and rebuild directly from migrations (ignores schema.rb)"
  task :rebuild do
    raise "Task not permitted in production." if ENV["RAILS_ENV"] == "production"

    puts "*** Deleting schema.rb"
    system "rm -f #{Rails.root.join("db", "schema.rb")}"

    puts "*** Deleting seed lock files"
    system "rm -f #{Rails.root.join("db", ".loaded*")}"

    puts "*** Recreate #{ENV['RAILS_ENV']} database"
    begin
      Rake::Task['environment'].invoke
      ActiveRecord::Base.connection
    rescue ActiveRecord::NoDatabaseError
      # database doesn't exist yet, just create it.
      Rake::Task["db:build"].invoke
    rescue Exception => e
      raise e
    else
      Rake::Task["db:environment:set"].invoke
      # https://github.com/rails/rails/issues/26319#issuecomment-244015760
      # ENV["DISABLE_DATABASE_ENVIRONMENT_CHECK"] = '1'
      Rake::Task["db:drop"].invoke
      Rake::Task["db:build"].invoke
    end
    Rake::Task["db:retest"].invoke
  end

  desc "Recreate the test DB"
  task :retest do
    system("rake db:drop db:build RAILS_ENV=test")
  end
end

Rationale - The problem with all the provided solutions is that native Rake tasks provided by Rails rely on schema.rb. When I am doing heavy data modeling, I make changes directly to the migration files; only after they've been committed upstream do we treat them as immutable. But if I make changes to the migration file, they aren't reflected in schema.rb.

The other problem is the distinction between dev and test environments. Rails db tasks handle them independently, but in my experience dev and test databases should always maintain parity, which means I had to run lots of duplicative database cleanup when developing.