I'm currently following the ruby on rails tutorial: http://guides.rubyonrails.org/getting_started.html.
I am trying to save data into the database. However, when I run: rails server I get the following error:
Migrations are pending. To resolve this issue, run: bin/rake db:migrate RAILS_ENV=development
I've looked at the other articles and when I run:
bin/rake db:migrate
I get a rake aborted!
After running:
rake db:abort_if_pending_migrations....
I see that:
You have 1 pending migration:
20150805200129 CreateDatabases
SQLite3::SQLException: table "databases" already exists:
and it just tells me to run rake db:migrate to start again.
It seems that it already exists. Is there a way to cancel the pending migration?
Sometimes, even dropping a local development database is not a good idea.
There are better ways to delete/destroy a specific migration in your Rails application.
You could use rails d migration command to destroy a particular migration:
rails d migration MigrationName
To undo the changes corresponding to a particular migration, you can use db:migrate:down method like this:
rake db:migrate:down VERSION=XXX
Sometimes, things could get more messy and in those situation another handy thing is to take a look at the schema_migrations table in your database which has all the migrations with their version saved in it.
You can delete a particular migration from this table like this:
delete from schema_migrations WHERE version = VERSION;
if you don't want that migration to be present anymore.
Your migration may have failed midway (so it created the table, but didn't finish).
You are just using development environment, so it's okay to just drop the database and rebuild it from scratch:
rake db:drop # THIS WILL DELETE YOUR DATABASE
rake db:create
rake db:migrate
If you are like me and maintain your database structure outside of Rails, you can just delete the migration file from db/migration. I got the error in the OP's question when I used the rails generate command to create a model class, forgetting that it also creates a migration file.
Do not use this method if you rely on Rails to maintain your database structure!
I keep my Rails structure file up to date by building it from the database using:
bundle exec rake db:structure:dump
I do not encourage to drop the database and start from the beginning especially when you already have the data inside the database.
My approach to this will be migrate first, then rollback. After that you can safely delete the migration file. So the procedure is as following.
rails db:migrate
rails db rollback
rm db/migrate/your_last_migration_file.rb
You can recreate database and run all migrations in your development environment with such command
rails db:migrate:reset
If you want to revert the wrong migrations, You can drop the whole db using this:
rake db:drop
Then remove the migrations file manually(This wont corrupt the db when you recreate as the Schema migrations would be dropped as well).
Then run
rake db:migrate
And if there is data to be seeded, then run this as well
rake db:setup
I recently started using Rails, and created a few Models using the CLI which in turn created some migrations.
I ran the rake db:migrate command after adding all my columns in there, and then realized that I'd left out the associations.
So what did I do?
I went ahead and edited the migrations to include those keys.
I ran rake db:migrate again, and nothing changed in the schema.
Then I ran rake db:reset and then rake db:setup.
When that didn't work, I deleted my schema.rb (the darn thing wouldn't get updated!) and tried recreating it. When I realized that didn't work, I dropped the database, and killed the schema.
Now I'm stuck with some manually modified migrations, no schema.rb and no database.
How do I get the modified migrations to generate a schema, and play nice with Rails?
In development it does not matter to drop and rebuild your database. I do it often and I even have a rake task for that. The 3 command to chain are:
rake db:drop
rake db:create
rake db:migrate
# And a 4rth optional command to rebuild your test database
rake db:test:prepare
With this you should be good
Next time you need to modify a migration manually after migrating it, you should process by:
rake db:rollback
edit your migration
rake db:migrate
Following those steps will save you some headaches
Bonus info:
After you deployed your migration to your production server you cannot manually modify it, hence you must write another migration that will perform the modification (adding columns, etc...)
Is there a quick rake db:rollback command for all of the migrations?
Rolling back all migrations
To rollback all migrations the best solution is the one #Claudio Floreani proposed:
rake db:migrate VERSION=0
This will rollback every migration. You can read why this is the best approach in his answer. Then, run all migrations again with
rake db:migrate
Resetting the database
Reset
rake db:migrate:reset #runs db:drop db:create db:migrate
This method drops the database and runs the migrations again.
Loading the last schema
rake db:reset
This method will drop the database and load the data from the last schema.
You can see more information in this post: Difference between rake db:migrate db:reset and db:schema:load
Thanks to #Claudio Floreani and all the users who commented to improve the answer.
If you really want to rollback all of the migrations, and not just take the database to a pristine state or to the last schema, you have to run:
rake db:migrate VERSION=0
This will actually rollback all the way down every migration and ensure that every migration is reversible.
If you now issue
rake db:migrate:status
you will see that all the migrations are still there but they are in a 'down' (not applied) state.
Other commands that imply a rake db:reset or rake db:drop (such as in the answers by #Orlando or #Alex Falke) won't do any rollback at all: that is, they won't ensure that every migration is reversible.
Moreover, rake db:drop cannot be run while the database is being accessed by other users, while rollbacks can be performed live (even if this is generally not recommended). And last but not least, simply dropping and recreating the database will also delete the schema migrations table: if someone runs rake db:migrate:status after the database has been dropped, he will be replied with "Schema migrations table does not exist yet" and will have no clues about which migrations can be applied (unless he knows it yet or can list them).
just use rake db:reset, that will drop your database (same as undoing all migrations) and reset to the last schema.
UPDATE: a more correct approach will be using rake db:migrate:reset. That will drop the database, create it again and run all the migrations, instead of resetting to the latest schema.
If a permission problem raises (like it happened to me), maybe you could try dropping all database tables like I did with rubymine (just open database tool window, select all tables and right-click -> drop), it should be similar with other IDEs. Some tables like sqlite_master and sqlite_sequence were conveniently ignored in the drop.
This allowed me to do
rails db:migrate
and everything worked fine. Of course you loose all data!
After adding migration files in the db/migrate folder and running rake db:migrate, I want get back to the previous step, I think using VERSION=n is the right way to do that, but I don't know the correct value of n to use. Is there any command to check the current n value?
It would be great if anyone could provide full instructions on how to use rake db:migrate.
For starters
rake db:rollback will get you back one step
then
rake db:rollback STEP=n
Will roll you back n migrations where n is the number of recent migrations you want to rollback.
More references here.
Roll back the most recent migration:
rake db:rollback
Roll back the n most recent migrations:
rake db:rollback STEP=n
You can find full instructions on the use of Rails migration tasks for rake on the Rails Guide for running migrations.
Here's some more:
rake db:migrate - Run all migrations that haven't been run already
rake db:migrate VERSION=20080906120000 - Run all necessary migrations (up or down) to get to the given version
rake db:migrate RAILS_ENV=test - Run migrations in the given environment
rake db:migrate:redo - Roll back one migration and run it again
rake db:migrate:redo STEP=n - Roll back the last n migrations and run them again
rake db:migrate:up VERSION=20080906120000 - Run the up method for the given migration
rake db:migrate:down VERSION=20080906120000 - Run the down method for the given migration
And to answer your question about where you get a migration's version number from:
The version is the numerical prefix on the migration's filename. For
example, to migrate to version 20080906120000 run
$ rake db:migrate VERSION=20080906120000
(From Running Migrations in the Rails Guides)
Best way is running Particular migration again by using down or up(in rails 4. It's change)
rails db:migrate:up VERSION=timestamp
Now how you get the timestamp.
Go to this path
/db/migrate
Identify migration file you want to revert.pick the timestamp from that file name.
If the version is 20150616132425, then use:
rails db:migrate:down VERSION=20150616132425
Other people have already answered you how to rollback, but you also asked how you could identify the version number of a migration.
rake db:migrate:status gives a list of your migrations version, name and status (up or down)
Your can also find the migration file, which contain a timestamp in the filename, that is the version number. Migrations are located in folder: /db/migrate
try {
$result=DB::table('users')->whereExists(function ($Query){
$Query->where('id','<','14162756');
$Query->whereBetween('password',[14162756,48384486]);
$Query->whereIn('id',[3,8,12]);
});
}catch (\Exception $error){
Log::error($error);
DB::rollBack(1);
return redirect()->route('bye');
}
I have the migration file db\migrate\20100905201547_create_blocks.rb.
How can I specifically rollback that migration file?
rake db:rollback STEP=1
Is a way to do this, if the migration you want to rollback is the last one applied. You can substitute 1 for however many migrations you want to go back.
For example:
rake db:rollback STEP=5
Will also rollback all the migration that happened later (4, 3, 2 and also 1).
To roll back all migrations back to (and including) a target migration, use: (This corrected command was added after all the comments pointing out the error in the original post)
rake db:migrate VERSION=20100905201547
In order to rollback only one specific migration (out of order) use:
rake db:migrate:down VERSION=20100905201547
Note that this will NOT rollback any interceding migrations -- only the one listed. If that is not what you intended, you can safely run rake db:migrate and it will re-run only that one, skipping any others that were not previously rolled back.
And if you ever want to migrate a single migration out of order, there is also its inverse db:migrate:up:
rake db:migrate:up VERSION=20100905201547
rake db:migrate:down VERSION=20100905201547
will roll back the specific file.
To find the version of all migrations, you can use this command:
rake db:migrate:status
Or, simply the prefix of the migration's file name is the version you need to rollback.
See the Ruby on Rails guide entry on migrations.
To rollback the last migration you can do:
rake db:rollback
If you want to rollback a specific migration with a version, you should do:
rake db:migrate:down VERSION=YOUR_MIGRATION_VERSION
For example, if the version is 20141201122027, you will do
rake db:migrate:down VERSION=20141201122027
to rollback that specific migration.
You can rollback your migration by using rake db:rollback with different options. The syntax will be different according to your requirements.
If you want to rollback just the last migration, then you can use either
rake db:rollback
or
rake db:rollback STEP=1
If you want rollback number of migrations at once, then you simply pass an argument:
rake db:rollback STEP=n
where n is number of migrations to rollback, counting from latest migration.
If you want to rollback to a specific migration, then you should pass the version of the migration in the following:
rake db:migrate:down VERSION=xxxxx
where xxxxx is the version number of the migration.
Use:
rake db:migrate:down VERSION=your_migrations's_version_number_here
The version is the numerical prefix on the migration's file name.
How to find the version:
Your migration files are stored in your rails_root/db/migrate directory. Find the appropriate file up to which you want to rollback and copy the prefix number.
For example:
File name: 20140208031131_create_roles.rb
Then the version is 20140208031131.
Rolling back the last migration:
# rails < 5.0
rake db:rollback
# rails >= 5.0
rake db:rollback
# or
rails db:rollback
Rolling back the last n number of migrations
# rails < 5.0
rake db:rollback STEP=2
# rails >= 5.0
rake db:rollback STEP=2
# or
rails db:rollback STEP=2
Rolling back a specific migration
# rails < 5.0
rake db:migrate:down VERSION=20100905201547
# rails >= 5.0
rake db:migrate:down VERSION=20100905201547
# or
rails db:migrate:down VERSION=20100905201547
To rollback the last migration you can do:
rake db:rollback
If you want to rollback a specific migration with a version you should do:
rake db:migrate:down VERSION=YOUR_MIGRATION_VERSION
If the migration file you want to rollback was called db/migrate/20141201122027_create_some_table.rb, then the VERSION for that migration is 20141201122027, which is the timestamp of when that migration was created, and the command to roll back that migration would be:
rake db:migrate:down VERSION=20141201122027
To roll back all migrations up to a particular version (e.g. 20181002222222), use:
rake db:migrate VERSION=20181002222222
(Note that this uses db:migrate -- not db:migrate:down as in other answers to this question.)
Assuming the specified migration version is older than the current version, this will roll back all migrations up to, but not including, the specified version.
For example, if rake db:migrate:status initially displays:
(... some older migrations ...)
up 20181001002039 Some migration description
up 20181002222222 Some migration description
up 20181003171932 Some migration description
up 20181004211151 Some migration description
up 20181005151403 Some migration description
Running:
rake db:migrate VERSION=20181002222222
Will result in:
(... some older migrations ...)
up 20181001002039 Some migration description
up 20181002222222 Some migration description
down 20181003171932 Some migration description
down 20181004211151 Some migration description
down 20181005151403 Some migration description
Reference: Migrate or revert only some migrations
If it is a reversible migration and the last one which has been executed, then run rake db:rollback. And you can always use the version.
For example, if the migration file is 20140716084539_create_customer_stats.rb, the rollback command will be:
rake db:migrate:down VERSION=20140716084539
If you are using Ruby on Rails 3
Step: 1 (check the last migration)
bundle exec rake db:migrate:status
Step: 2 (roll back the last migration)
bundle exec rake db:rollback
Now, you can revert the migration with safety one by one.
For a specific migration
rails d migration <migration_name>
For reverting multiple migrations
bundle exec rake db:rollback STEP=n
where n is how many migrations you want to rollback.
Example: bundle exec rake db:rollback STEP=5
A migration file looks like this,
20221213051020_my_migrations
In this case, the model name should be MyMigration. The migration ends with a plural word, so it ends with migrations.
To roll back this particular migration, you have to understand that the first part of the migration name (number in front of the migration name) is the migration number.
To roll back this migration, just open the terminal and write,
rake db:migrate:down VERSION=migration_number
So finally, you have to actually type in the terminal to roll back this particular migration,
Write the below command on terminal to rollback a particular migration, upper command is just to explain you
rake db:migrate:down VERSION=20221213051020
Just remember that each migration has a different migration number, so watch carefully and copy paste or type manually.
Migrations change the state of the database using the command
bundle exec rake db:migrate
We can undo a single migration step using
bundle exec rake db:rollback
To go all the way back to the beginning, we can use
bundle exec rake db:migrate VERSION=0
As you might guess, substituting any other number for 0 migrates to that version number, where the version numbers come from listing the migrations sequentially.
Well, in rails 5 it's quite easy
rake db:migrate:status
or
rails db:migrate:status
It was modified to handle both the same way.
Then just pick which version you want to roll back
and then run
rake db:migrate VERSION=2013424230423
Make sure VERSION is all capital letters.
If you have a problem with any step of the migration or stuck in the middle simply, go to the migration file and comment out the lines that were already migrated.
If you want to rollback and migrate you can run:
rake db:migrate:redo
That's the same as:
rake db:rollback
rake db:migrate
I found these steps most useful.
To check for status, run rails db:migrate:status. Then you'll have a good view of the migrations you want to remove.
Then, run rails db:rollback to revert the changes one by one. After doing so, you can check the status again to be fully confident.
Next, if you want to remove or delete. Run rails d migration <migration_name>. This would clean up the versions you created.
After that's done, you can proceed to making new changes.
For a multiple databases configurations (RoR >= v6), you must append the database name in the command, like:
rails db:rollback:primary, where primary is the name of the database in your config/databases.yml file, to roll back the last migration. You can make usage of the STEPS attribute here, as usual.
rails db:migrate:down:primary VERSION=your_migration_timestamp, to revert only the provided migration version. Here primary is the name of the database too.
In addition:
When a migration you deployed long ago does not let you migrate a new one.
I work in a larger Ruby on Rails application with more than a thousand of migration files. And, it takes a month for us to ship a medium-sized feature. I was working on a feature and I had deployed a migration a month ago, and then in the review process the structure of migration and filename changed, now I try to deploy my new code, the build failed saying:
ActiveRecord::StatementInvalid: PG::DuplicateColumn: ERROR: column "my_new_field" of relation "accounts" already exists
None of the above-mentioned solutions worked for me, because the old migration file was missing and the field I intended to create in my new migration file already existed in the database. The only solution that worked for me is:
I scped the file to the server
I opened the rails console
I required the file in the IRB session
then AddNewMyNewFieldToAccounts.new.down
And then I could run the deploy build again.
You can run down migration command to rollback the migration like below:
rake db:migrate:down VERSION=20100905201547
If you want to revert from the last migration, use the rake db:rollback command. It's working fine for me!