How to rollback a specific migration

Question

I have the following migration file db migrate 20100905201547 create blocks rb  How can I specifically rollback that migration file

User · Answer

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 version   Your migration files are stored in your rails root db migrate directory  Find 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

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From Rails Guide  Reverting Previous Migrations  You can use Active Record s ability to rollback migrations using the revert method   require relative  20100905201547 create blocks   class FixupCreateBlock  lt  ActiveRecord  Migration   def change     revert CreateBlock      create table  apples  do  t        t string  variety     end   end end   The revert method also accepts a block of instructions to reverse  This could be useful to revert selected parts of previous migrations  For example  let s imagine that CreateBlock is committed and it is later decided it would be best to use Active Record validations  in place of the CHECK constraint  to verify the zipcode       class DontUseConstraintForZipcodeValidationMigration  lt  ActiveRecord  Migration       def change         revert do             copy-pasted code from CreateBlock           reversible do  dir              dir up do                 add a CHECK constraint               execute  lt  lt -SQL                 ALTER TABLE distributors                   ADD CONSTRAINT zipchk                     CHECK  char length zipcode    5                 SQL             end             dir down do               execute  lt  lt -SQL                 ALTER TABLE distributors                   DROP CONSTRAINT zipchk               SQL             end           end              The rest of the migration was ok         end       end     end   The same migration could also have been written without using revert but this would have involved a few more steps  reversing the order of create table and reversible  replacing create table by drop table  and finally replacing up by down and vice-versa  This is all taken care of by revert

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In Addition When migration you deployed long ago does not let you migrate new one  What happened is  I work in a larger Rails app 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 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  quot my new field quot  of relation  quot accounts quot  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 DB  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  then I could run the deploy build again  Hope it helps you too

User · Answer

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    Hope that helps

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If it is a reversible migration and the last one which has been executed  then run rake db rollback  And you can always use version  e g  the migration file is 20140716084539 create customer stats rb so the rollback command will be  rake db migrate down VERSION 20140716084539

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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

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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

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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

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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 e g  if the version is 20141201122027  you will do   rake db migrate down VERSION 20141201122027   to rollback that specific migration

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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

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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

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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

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Rolling back last migration     rails  lt  5 0 rake db rollback    rails  gt   5 0 rake db rollback   or rails db rollback   Rolling back last n number of migrations    rails  lt  5 0 rake db rollback STEP 2    rails  gt   5 0 rake db rollback STEP 2   or rails db rollback STEP 2   Rolling back a specific migration     rails  lt  5 0 rake db migrate down VERSION 20100905201547    rails  gt   5 0 rake db migrate down VERSION 20100905201547   or rails db migrate down VERSION 20100905201547

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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  https   makandracards com makandra 845-migrate-or-revert-only-some-migrations

[ruby-on-rails] How to rollback a specific migration?

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