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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'm writing my first Rails app. I've run a few rails generate model ... and rake db:migrate commands, but I now want to change my data model and so need to undo a few migrations.
The docs say I can undo a migration with rake db:rollback, but this isn't working. When I run this in the console the computer thinks for a few seconds but doesn't make any changes to db/migrate/ or db/migrate/schema.rb. No output is printed to the console.
Is this behavior correct? Shouldn't db:rollback be changing my schema? If so, can anyone think why it might not be working?
I'm on Rails v. 3.2.6.
EDIT
At the moment rake db:migrate:status gives
database: db/development.sqlite3
Status Migration ID Migration Name
--------------------------------------------------
up 20120617191211 Create irs
up 20120701154357 Create paths
up 20120701154421 Create nodes
up 20120702151447 ********** NO FILE **********
down 20120702155140 Create venues
down 20120703233833 Remove path from venues
Solution (see my comment): run
rake db:migrate:status
and correct problems you find there. In this case (per #MarkThomas' followup), you might want to check all files you need are in place.
This is what worked for me. Combine the steps given in this answer and comment by dB.
run rake db:migrate:status
If you have a ****NO FILE**** entry, just note the version number as noFileVersion. Note the version of the entry just above no file entry(stable_version).
created a "dummy" file with name noFileVersion_create_nothing.rb, and body
class CreateNothing < ActiveRecord::Migration[6.0]
def change
end
end
run rake db:migrate VERSION=stable_version
remove the noFileVersion_create_nothing.rb manually.
run rake db:migrate.
run rake db:migrate:status again to check if No file entry has disappeared.
The following worked for me:
rake db:migrate:down VERSION=20190304092208
Version number can be obtained by the following command:
rake db:migrate:status
This was the last version number to rollback one last migration
NOTE: Use the suggestions with caution, it is very dangerous for non-dev environments.
If
rake db:migrate:status
gives you a migration that says
up 20120702151447 ********** NO FILE **********
Then the best thing to do would be to do a (note that the following command will drop the database):
rake db:reset
to redo all migrations. If the last migration is the one missing, then schema.rb will have the last migration that rake db:migrate will look for:
ActiveRecord::Schema.define(:version => 20120702151447) do
Change that number to the last one in your migrate folder.
I have created a migration file for creating a table UserDetails in my db.. and it was working fine b4...
Unknowingly I deleted that table to do some modification .. But now when i gave
rake db:migrate .. its not creating the table ..
I have the migration file .. BUt when i give rake db:migrate its not creating.. How to do so ??
Rails maintains a 'schema_migrations' table to know what migrations have already run and will not run the migrations that have already been completed. Since, you had already run the migration once, it would have updated the 'schema_migrations' table with the version no. of the migration. You can do rake db:rollback to revert the last migration run or rake db:migrate:down VERSION=<version_number> to revert any migration that was run before.
Now, I suggest if you know the version no (Time stamp of the file), you can manually delete from 'schema_migrations' table and re-run db:migrate.
Rake stores the time of the most recent migration inside the database - if the migration you're trying to run is older than that, it won't run with rake db:migrate.
I don't know how to run a specific migration manually, sorry :/
Could you just run that specific migration as stated in the Guides. http://guides.rubyonrails.org/migrations.html#being-specific
I have run specific migrations by their timestamp before. It seems like it would work in this situation also.
I would like to remove/delete a migration file. How would I go about doing that? I know there are similar questions on here but as an update, is there a better way than doing script/destroy?
Also, should I do a db:reset or db:drop if I remove/delete a migration?
I usually:
Perform a rake db:migrate VERSION=XXX on all environments, to the version before the one I want to delete.
Delete the migration file manually.
If there are pending migrations (i.e., the migration I removed was not the last one), I just perform a new rake db:migrate again.
If your application is already on production or staging, it's safer to just write another migration that destroys your table or columns.
Another great reference for migrations is: http://guides.rubyonrails.org/migrations.html
Another way to delete the migration:
$ rails d migration SameMigrationNameAsUsedToGenerate
Use it before rake db:migrate is executed because changes in database will stay forever :) - or remove changes in Database manually
Run below commands from app's home directory:
rake db:migrate:down VERSION="20140311142212" (here version is the timestamp prepended by rails when migration was created. This action will revert DB changes due to this migration)
Run "rails destroy migration migration_name" (migration_name is the one use chose while creating migration. Remove "timestamp_" from your migration file name to get it)
None of these answers quite fit the problem i had as the migration i wanted to delete was missing:
I had created and run a migration in some other branch, which was then discarded. The problem is when a migration is run, rails adds the version into a schema_migrations table in the database. So even if it isn't listed in your db structure or schema, rails looks for it.
You can reveal these orphaned migrations by running:
rails db:migrate:status
Note the versions of the missing migrations and head into the db console:
rails dbconsole
Now remove the versions from the migration table manually:
delete from schema_migrations where version='<version>';
You should now be good.
You can also run a down migration like so:
rake db:migrate:down VERSION=versionnumber
Refer to the Ruby on Rails guide on migrations for more info.
We can use,
$ rails d migration table_name
Which will delete the migration.
Sometimes I found myself deleting the migration file and then deleting the corresponding entry on the table schema_migrations from the database. Not pretty but it works.
This also works in Rails 5.
If the migration was the most recent one you can remove the database column(s) that the migration added by doing:
rake db:rollback
then remove the migration file itself by running:
rails d migration WhateverYourMigrationWasNamed.rb
Look at 4.1 Rolling Back
http://guides.rubyonrails.org/migrations.html
$ rake db:rollback
I just had this same problem:
rails d migration fuu
-this deleted the migration with the last timestamp
rails d migration fuu
-this deleted the other migration
use git status to check that is not on the untracked files anymore
rails g migration fuu
That fixed it for me
Side Note:
Starting at rails 5.0.0
rake has been changed to rails
So perform the following
rails db:migrate VERSION=0
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!