Difference between rake db migrate db reset and db schema load

Question

The difference between rake db migrate and rake db reset is pretty clear in my head  The thing which I don t understand is how rake db schema load 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    Please help to clarify  if my understanding has gone wrong

User · Answer

You could simply look in the Active Record Rake tasks as that is where I believe they live as in this file. https://github.com/rails/rails/blob/fe1f4b2ad56f010a4e9b93d547d63a15953d9dc2/activerecord/lib/active_record/tasks/database_tasks.rb

What they do is your question right?

That depends on where they come from and this is just and example to show that they vary depending upon the task. Here we have a different file full of tasks.

https://github.com/rails/rails/blob/fe1f4b2ad56f010a4e9b93d547d63a15953d9dc2/activerecord/Rakefile

which has these tasks.

namespace :db do
  task create: ["db:mysql:build", "db:postgresql:build"]
  task drop: ["db:mysql:drop", "db:postgresql:drop"]
end

This may not answer your question but could give you some insight into go ahead and look the source over especially the rake files and tasks. As they do a pretty good job of helping you use rails they don't always document the code that well. We could all help there if we know what it is supposed to do.

User · Answer

As far as I understand  it is going to drop your database and re-create it based on your db schema rb file  That is why you need to make sure that your schema rb file is always up to date and under version control

User · Answer

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 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

User · Answer

TLDR Use  rake db migrate If you wanna make changes to the schema rake db reset If you wanna drop the database  reload the schema from schema rb  and reseed the database rake db schema load If you wanna reset database to schema as provided in schema rb  This will delete all data   Explanations 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 load will 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 Relevant part of the commands from databases rake  namespace  schema do   desc  Creates a db schema rb file that is portable against any DB supported by Active Record    task  dump   gt    environment   load config  do     require  active record schema dumper      filename   ENV  SCHEMA      File join ActiveRecord  Tasks  DatabaseTasks db dir   schema rb       File open filename   quot w utf-8 quot   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   gt    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   gt     db drop    db setup      namespace  migrate do     desc   Rollbacks the database one migration and re migrate up  options  STEP x  VERSION x      task  redo   gt    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

User · Answer

Rails 5 db create - Creates the database for the current RAILS ENV environment  If RAILS ENV is not specified it defaults to the development and test databases  db create all - Creates the database for all environments  db drop - Drops the database for the current RAILS ENV environment  If RAILS ENV is not specified it defaults to the development and test databases  db drop all - Drops the database for all environments  db migrate - Runs migrations for the current environment that have not run yet  By default it will run migrations only in the development environment  db migrate redo - Runs db migrate down and db migrate up or db migrate rollback and db migrate up depending on the specified migration  db migrate up - Runs the up for the given migration VERSION  db migrate down - Runs the down for the given migration VERSION  db migrate status - Displays the current migration status  db migrate rollback - Rolls back the last migration  db version - Prints the current schema version  db forward - Pushes the schema to the next version  db seed - Runs the db seeds rb file  db schema load Recreates the database from the schema rb file  Deletes existing data  db schema dump Dumps the current environment   s schema to db schema rb  db structure load - Recreates the database from the structure sql file  db structure dump - Dumps the current environment   s schema to db structure sql   You can specify another file with SCHEMA db my structure sql  db setup Runs db create  db schema load and db seed  db reset Runs db drop and db setup  db migrate reset - Runs db drop  db create and db migrate  db test prepare - Check for pending migrations and load the test schema   If you run rake without any arguments it will do this by default   db test clone - Recreate the test database from the current environment   s database schema  db test clone structure - Similar to db test clone  but it will ensure that your test database has the same structure  including charsets and collations  as your current environment   s database  db environment set - Set the current RAILS ENV environment in the ar internal metadata table   Used as part of the protected environment check   db check protected environments - Checks if a destructive action can be performed in the current RAILS ENV environment  Used internally when running a destructive action such as db drop or db schema load

[ruby-on-rails] Difference between rake db:migrate db:reset and db:schema:load

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