In Rails 5, how to drop the default value of primary key i.e. 'id' column and make it auto_increment again?

Question

In my rails application, there is a table with 'id' column default value set to 0. I want to drop this default value and make this column auto-increment again. I have tried

change_column_default(:table_name, :id, nil)

but it doesn't seem to work on primary key such as 'id'

You just want to reset it to `0` after deleting all the table's records ? — Roc Khalil, Mar 03 '20 at 10:28
No, I don't want to remove any records from the table. I just want to drop the `default` i.e. 0 and want to make it again auto-incrementing — Mohsin Sethi, Mar 04 '20 at 11:44
they already have ids assigned to them so new records should automatically get incremental ids assigned to them. — Mohsin Sethi, Mar 05 '20 at 10:45

score 0 · Answer 1 · answered Mar 03 '20 at 09:25

0

Try to use

change_column :tabel_name, :column_name, :string, :default => nil

answered Mar 03 '20 at 09:25

DenicioCode

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Same result as of `change_column_default` – Mohsin Sethi Mar 03 '20 at 09:32
can you share you schema.rb or structure.sql Is the default set there? – DenicioCode Mar 03 '20 at 10:55
this is the line in `schema.rb` that is setting the `default value` ```create_table "table_name", id: :integer, default: 0, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|``` – Mohsin Sethi Mar 04 '20 at 11:46

score 0 · Answer 2 · answered Mar 26 '21 at 16:42

That's work for me:

class MigrationName < ActiveRecord::Migration[6.0]
  def up
    max_id = TableName.maximum(:id) || 0
    execute "CREATE SEQUENCE IF NOT EXISTS \"table_name_id_seq\" START #{max_id + 1}"
    change_column_default :table_name, :id, -> { "nextval('table_name_id_seq'::regclass)" }
  end

  def down
    change_column_default :table_name, :id, nil
    execute 'DROP SEQUENCE "table_name_id_seq"'
  end
end

In Rails 5, how to drop the default value of primary key i.e. 'id' column and make it auto_increment again?

2 Answers2