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The difference between rake db:migrate and rake db:reset is pretty clear to me. The thing which I don't understand is how rake db:schema:load is different from the former two.
Just to be sure that I am on the same page:
rake db:migrate - Runs the migrations which haven't been run yet.rake db:reset - Clears the database (presumably does a rake db:drop + rake db:create + rake db:migrate) and runs migration on a fresh database.
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A migration means that you move from the current version to a newer version (as is said in the first answer). Using rake db:migrate you can apply any new changes to your schema. But if you want to rollback to a previous migration you can use rake db:rollback to nullify your new changes if they are incorrectly defined.
A Rails migration is a tool for changing an application's database schema. Instead of managing SQL scripts, you define database changes in a domain-specific language (DSL). The code is database-independent, so you can easily move your app to a new platform.
The schema. rb serves mainly two purposes: It documents the final current state of the database schema. Often, especially when you have more than a couple of migrations, it's hard to deduce the schema just from the migrations alone. With a present schema.
db:migrate runs (single) migrations that have not run yet.
db:create creates the database
db:drop deletes the database
db:schema:load creates tables and columns within the existing database following schema.rb. This will delete existing data.
db:setup does db:create, db:schema:load, db:seed
db:reset does db:drop, db:setup
db:migrate:reset does db:drop, db:create, db:migrate
Typically, you would use db:migrate after having made changes to the schema via new migration files (this makes sense only if there is already data in the database). db:schema:load is used when you setup a new instance of your app.
I hope that helps.
UPDATE for rails 3.2.12:
I just checked the source and the dependencies are like this now:
db:create creates the database for the current env
db:create:all creates the databases for all envs
db:drop drops the database for the current env
db:drop:all drops the databases for all envs
db:migrate runs migrations for the current env that have not run yet
db:migrate:up runs one specific migration
db:migrate:down rolls back one specific migration
db:migrate:status shows current migration status
db:rollback rolls back the last migration
db:forward advances the current schema version to the next one
db:seed (only) runs the db/seed.rb file
db:schema:load loads the schema into the current env's database
db:schema:dump dumps the current env's schema (and seems to create the db as well)
db:setup runs db:create db:schema:load db:seed
db:reset runs db:drop db:setup
db:migrate:redo runs (db:migrate:down db:migrate:up) or (db:rollback db:migrate) depending on the specified migration
db:migrate:reset runs db:drop db:create db:migrate
For further information please have a look at https://github.com/rails/rails/blob/v3.2.12/activerecord/lib/active_record/railties/databases.rake (for Rails 3.2.x) and https://github.com/rails/rails/blob/v4.0.5/activerecord/lib/active_record/railties/databases.rake (for Rails 4.0.x)
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Use
rake db:migrate If you wanna make changes to the schemarake db:reset If you wanna drop the database, reload the schema from schema.rb, and reseed the databaserake db:schema:load If you wanna reset database to schema as provided in schema.rb (This will delete all data)rake db:schema:load will set up the schema as provided in schema.rb file. This is useful for a fresh install of app as it doesn't take as much time as db:migrate
Important note,
db:schema:loadwill delete data on server.
rake db:migrate makes changes to the existing schema. Its like creating versions of schema. db:migrate will look in db/migrate/ for any ruby files and execute the migrations that aren't run yet starting with the oldest. Rails knows which file is the oldest by looking at the timestamp at the beginning of the migration filename. db:migrate comes with a benefit that data can also be put in the database. This is actually not a good practice. Its better to use rake db:seed to add data.
rake db:migrate provides tasks up, down etc which enables commands like rake db:rollback and makes it the most useful command.
rake db:reset does a db:drop and db:setup
It drops the database, create it again, loads the schema, and initializes with the seed data
namespace :schema do desc 'Creates a db/schema.rb file that is portable against any DB supported by Active Record' task :dump => [:environment, :load_config] do require 'active_record/schema_dumper' filename = ENV['SCHEMA'] || File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, 'schema.rb') File.open(filename, "w:utf-8") do |file| ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file) end db_namespace['schema:dump'].reenable end desc 'Loads a schema.rb file into the database' task :load => [:environment, :load_config, :check_protected_environments] do ActiveRecord::Tasks::DatabaseTasks.load_schema_current(:ruby, ENV['SCHEMA']) end # desc 'Drops and recreates the database from db/schema.rb for the current environment and loads the seeds.' task :reset => [ 'db:drop', 'db:setup' ] namespace :migrate do # desc 'Rollbacks the database one migration and re migrate up (options: STEP=x, VERSION=x).' task :redo => [:environment, :load_config] do if ENV['VERSION'] db_namespace['migrate:down'].invoke db_namespace['migrate:up'].invoke else db_namespace['rollback'].invoke db_namespace['migrate'].invoke end end If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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