Converts an ActsAsTaggableOn database structure for use with Gutentag

00000000000000_convert_to_gutentag.gutentag.rb

# frozen_string_literal: true

# adapted from Gutentag's install migrations
# https://github.com/pat/gutentag

superclass = ActiveRecord::VERSION::MAJOR < 5 ?
  ActiveRecord::Migration : ActiveRecord::Migration[4.2]
class ConvertToGutentag < superclass
  def up
    ## taggings
    # delete indexes
    ActiveRecord::Base.connection.indexes(:taggings).map(&:name).uniq.each do |index|
      remove_index(:taggings, name: index) unless index == 'PRIMARY'
    end

    rename_table :taggings, :gutentag_taggings

    # Gutentag uses t.timestamps, while AATO just uses created_at
    add_column :gutentag_taggings, :updated_at, :datetime, null: false
    Gutentag::Tagging.update_all('updated_at = created_at')

    # no contexts or taggers in Gutentag
    remove_column :gutentag_taggings, :tagger_id
    remove_column :gutentag_taggings, :tagger_type
    remove_column :gutentag_taggings, :context

    # not set in AATO
    change_column_null :gutentag_taggings, :tag_id, false
    change_column_null :gutentag_taggings, :taggable_id, false
    change_column_null :gutentag_taggings, :taggable_type, false

    # rebuild the indexes Gutentag expects
    add_index :gutentag_taggings, :tag_id
    add_index :gutentag_taggings, [:taggable_type, :taggable_id]
    add_index :gutentag_taggings, [:taggable_type, :taggable_id, :tag_id], unique: true, name: 'unique_taggings'

    ## tags
    remove_index :tags, :name

    rename_table :tags, :gutentag_tags

    change_column_null :gutentag_tags, :name, false
    change_column_null :gutentag_tags, :taggings_count, false

    # no timestamps at all on AATO tags
    add_timestamps :gutentag_tags, null: false

    add_index :gutentag_tags, :name, unique: true
    add_index :gutentag_tags, :taggings_count
  end

  def down
    raise ActiveRecord::IrreversibleMigration
  end
end