Adding default true to boolean in existing Rails column

Question

I ve seen a few questions  namely this one  here on SO about adding a default boolean value to an existing column  So I tried the change column suggestion but I mustn t be doing it right   I tried     change column  profiles   show attribute   boolean   default   gt  true   Which returns -bash  change column  command not found  I then ran     rails g change column  profiles   show attribute   boolean   default   gt  true      and    rails change column  profiles   show attribute   boolean   default   gt  true   Then ran rake db migrate  but the value for  show attribute remained nil  In the question I referenced above it says in PostgreSQL you need to update it manually  Since I m using PostgreSQL I added the following in my create profiles migration   t boolean  show attribute   default   gt  true   Can someone tell me what I m doing wrong here

User · Answer

change column  things   price 1   integer  default  123  null  false   Seems to be best way to add a default to an existing column that doesn t have null  false already   Otherwise   change column  things   price 1   integer  default  123   Some research I did on this   https   gist github com Dorian 417b9a0e1a4e09a558c39345d50c8c3b

User · Answer

As a variation on the accepted answer you could also use the change column default method in your migrations   def up   change column default  profiles   show attribute  true end  def down   change column default  profiles   show attribute  nil end   Rails API-docs

User · Answer

change column is a method of ActiveRecord  Migration  so you can t call it like that in the console  If you want to add a default value for this column  create a new migration  rails g migration add default value to show attribute Then in the migration created    That s the more generic way to change a column def up   change column  profiles   show attribute   boolean  default  true end  def down   change column  profiles   show attribute   boolean  default  nil end  OR a more specific option  def up     change column default  profiles   show attribute  true end  def down     change column default  profiles   show attribute  nil end  Then run rake db migrate  It won t change anything to the already created records  To do that you would have to create a rake task or just go in the rails console and update all the records  which I would not recommend in production   When you added t boolean  show attribute   default   gt  true to the create profiles migration  it s expected that it didn t do anything  Only migrations that have not already been ran are executed  If you started with a fresh database  then it would set the default to true

User · Answer

If you don t want to create another migration-file for a small  recent change - from Rails Console   ActiveRecord  Migration change column  profiles   show attribute   boolean   default   gt  true   Then exit and re-enter rails console  so DB-Changes will be in-effect   Then  if you do this      Profile new     You should see the  show attribute  default-value as true   For existing records  if you want to preserve existing  false  settings and only update  nil  values to your new default   Profile all each  profile  profile update attributes  show attribute   gt   profile show attribute    nil   true   false        Update the migration that created this table  so any future builds of the DB will get it right from the onset   Also run the same process on any deployed-instances of the DB     If using the  new db migration  method  you can do the update of existing nil-values in that migration

User · Answer

If you just made a migration  you can rollback and then make your migration again   To rollback you can do as many steps as you want   rake db rollback STEP 1   Or  if you are using Rails 5 2 or newer   rails db rollback STEP 1   Then  you can just make the migration again   def change   add column  profiles   show attribute   boolean  default  true end   Don t forget to rake db migrate and if you are using heroku heroku run rake db migrate

User · Answer

Also  as per the doc      default cannot be specified via command line   https   guides rubyonrails org active record migrations html  So there is no ready-made rails generator  As specified by above answers  you have to fill manually your migration file with the change column default method   You could create your own generator  https   guides rubyonrails org generators html

User · Answer

I m not sure when this was written  but currently to add or remove a default from a column in a migration  you can use the following   change column null  products   name  false   Rails 5   change column default  products   approved  from  true  to  false   http   edgeguides rubyonrails org active record migrations html changing-columns  Rails 4 2    change column default  products   approved  false   http   guides rubyonrails org v4 2 active record migrations html changing-columns  Which is a neat way of avoiding looking through your migrations or schema for the column specifications

[ruby-on-rails-3] Adding :default => true to boolean in existing Rails column

Examples related to ruby-on-rails-3

Examples related to migration