How do you write a migration to rename an ActiveRecord model and its table in Rails

Question

I m terrible at naming and realize that there are a better set of names for my models in my Rails app  Is there any way to use a migration to rename a model and its corresponding table

User · Answer

You can do execute this command   rails g migration  rename  old table name to new table name   after you edit the file and add this code in the method change  rename table   old table name     new table name

User · Answer

Here s an example   class RenameOldTableToNewTable  lt  ActiveRecord  Migration   def self up     rename table  old table name   new table name   end    def self down     rename table  new table name   old table name   end end   I had to go and rename the model declaration file manually   Edit   In Rails 3 1  amp  4  ActiveRecord  Migration  CommandRecorder knows how to reverse rename table migrations  so you can do this   class RenameOldTableToNewTable  lt  ActiveRecord  Migration   def change     rename table  old table name   new table name   end  end    You still have to go through and manually rename your files

User · Answer

In Rails 4 all I had to do was the def change  def change   rename table  old table name   new table name end   And all of my indexes were taken care of for me  I did not need to manually update the indexes by removing the old ones and adding new ones   And it works using the change for going up or down in regards to the indexes as well

User · Answer

Here s an example   class RenameOldTableToNewTable  lt  ActiveRecord  Migration   def self up     rename table  old table name   new table name   end    def self down     rename table  new table name   old table name   end end   I had to go and rename the model declaration file manually   Edit   In Rails 3 1  amp  4  ActiveRecord  Migration  CommandRecorder knows how to reverse rename table migrations  so you can do this   class RenameOldTableToNewTable  lt  ActiveRecord  Migration   def change     rename table  old table name   new table name   end  end    You still have to go through and manually rename your files

User · Answer

In Rails 4 all I had to do was the def change  def change   rename table  old table name   new table name end   And all of my indexes were taken care of for me  I did not need to manually update the indexes by removing the old ones and adding new ones   And it works using the change for going up or down in regards to the indexes as well

User · Answer

You can do execute this command   rails g migration  rename  old table name to new table name   after you edit the file and add this code in the method change  rename table   old table name     new table name

User · Answer

The other answers and comments covered table renaming  file renaming  and grepping through your code   I d like to add a few more caveats   Let s use a real-world example I faced today  renaming a model from  Merchant  to  Business     Don t forget to change the names of dependent tables and models in the same migration  I changed my Merchant and MerchantStat models to Business and BusinessStat at the same time  Otherwise I d have had to do way too much picking and choosing when performing search-and-replace  For any other models that depend on your model via foreign keys  the other tables  foreign-key column names will be derived from your original model name  So you ll also want to do some rename column calls on these dependent models  For instance  I had to rename the  merchant id  column to  business id  in various join tables  for has and belongs to many relationship  and other dependent tables  for normal has one and has many relationships   Otherwise I would have ended up with columns like  business stat merchant id  pointing to  business id   Here s a good answer about doing column renames  When grepping  remember to search for singular  plural  capitalized  lowercase  and even UPPERCASE  which may occur in comments  versions of your strings  It s best to search for plural versions first  then singular  That way if you have an irregular plural - such as in my merchants    businesses example - you can get all the irregular plurals correct  Otherwise you may end up with  for example   businesss   3 s s  as an intermediate state  resulting in yet more search-and-replace  Don t blindly replace every occurrence  If your model names collide with common programming terms  with values in other models  or with textual content in your views  you may end up being too over-eager  In my example  I wanted to change my model name to  Business  but still refer to them as  merchants  in the content in my UI  I also had a  merchant  role for my users in CanCan - it was the confusion between the merchant role and the Merchant model that caused me to rename the model in the first place

User · Answer

You also need to replace your indexes   class RenameOldTableToNewTable lt  ActiveRecord Migration   def self up     remove index  old table name   column name     rename table  old table name   new table name     add index  new table name   column name   end     def self down     remove index  new table name   column name     rename table  new table name   old table name     add index  old table name   column name   end end   And rename your files etc  manually as other answers here describe   See  http   api rubyonrails org classes ActiveRecord Migration html  Make sure you can rollback and roll forward after you write this migration  It can get tricky if you get something wrong and get stuck with a migration that tries to effect something that no longer exists  Best trash the whole database and start again if you can t roll back  So be aware you might need to back something up   Also  check schema db for any relevant column names in other tables defined by a has  or belongs to or something  You ll probably need to edit those too   And finally  doing this without a regression test suite would be nuts

User · Answer

You also need to replace your indexes   class RenameOldTableToNewTable lt  ActiveRecord Migration   def self up     remove index  old table name   column name     rename table  old table name   new table name     add index  new table name   column name   end     def self down     remove index  new table name   column name     rename table  new table name   old table name     add index  old table name   column name   end end   And rename your files etc  manually as other answers here describe   See  http   api rubyonrails org classes ActiveRecord Migration html  Make sure you can rollback and roll forward after you write this migration  It can get tricky if you get something wrong and get stuck with a migration that tries to effect something that no longer exists  Best trash the whole database and start again if you can t roll back  So be aware you might need to back something up   Also  check schema db for any relevant column names in other tables defined by a has  or belongs to or something  You ll probably need to edit those too   And finally  doing this without a regression test suite would be nuts

User · Answer

Here s an example   class RenameOldTableToNewTable  lt  ActiveRecord  Migration   def self up     rename table  old table name   new table name   end    def self down     rename table  new table name   old table name   end end   I had to go and rename the model declaration file manually   Edit   In Rails 3 1  amp  4  ActiveRecord  Migration  CommandRecorder knows how to reverse rename table migrations  so you can do this   class RenameOldTableToNewTable  lt  ActiveRecord  Migration   def change     rename table  old table name   new table name   end  end    You still have to go through and manually rename your files

User · Answer

Here s an example   class RenameOldTableToNewTable  lt  ActiveRecord  Migration   def self up     rename table  old table name   new table name   end    def self down     rename table  new table name   old table name   end end   I had to go and rename the model declaration file manually   Edit   In Rails 3 1  amp  4  ActiveRecord  Migration  CommandRecorder knows how to reverse rename table migrations  so you can do this   class RenameOldTableToNewTable  lt  ActiveRecord  Migration   def change     rename table  old table name   new table name   end  end    You still have to go through and manually rename your files

User · Answer

The other answers and comments covered table renaming  file renaming  and grepping through your code   I d like to add a few more caveats   Let s use a real-world example I faced today  renaming a model from  Merchant  to  Business     Don t forget to change the names of dependent tables and models in the same migration  I changed my Merchant and MerchantStat models to Business and BusinessStat at the same time  Otherwise I d have had to do way too much picking and choosing when performing search-and-replace  For any other models that depend on your model via foreign keys  the other tables  foreign-key column names will be derived from your original model name  So you ll also want to do some rename column calls on these dependent models  For instance  I had to rename the  merchant id  column to  business id  in various join tables  for has and belongs to many relationship  and other dependent tables  for normal has one and has many relationships   Otherwise I would have ended up with columns like  business stat merchant id  pointing to  business id   Here s a good answer about doing column renames  When grepping  remember to search for singular  plural  capitalized  lowercase  and even UPPERCASE  which may occur in comments  versions of your strings  It s best to search for plural versions first  then singular  That way if you have an irregular plural - such as in my merchants    businesses example - you can get all the irregular plurals correct  Otherwise you may end up with  for example   businesss   3 s s  as an intermediate state  resulting in yet more search-and-replace  Don t blindly replace every occurrence  If your model names collide with common programming terms  with values in other models  or with textual content in your views  you may end up being too over-eager  In my example  I wanted to change my model name to  Business  but still refer to them as  merchants  in the content in my UI  I also had a  merchant  role for my users in CanCan - it was the confusion between the merchant role and the Merchant model that caused me to rename the model in the first place

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