metamaps--metamaps/db/migrate/20151001024122_mapping_polymorphism.rb

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class MappingPolymorphism < ActiveRecord::Migration
def up
add_column :mappings, :mappable_id, :integer
add_column :mappings, :mappable_type, :string
add_index :mappings, [:mappable_id, :mappable_type]
Mapping.find_each do |mapping|
if mapping.synapse_id.nil? and mapping.topic_id.nil?
puts "Mapping id=#{mapping.id} has no valid id, skipping!"
next
end
if not mapping.synapse_id.nil? and not mapping.topic_id.nil?
puts "Mapping id=#{mapping.id} has both topic and synapse ids, skipping!"
next
end
unless mapping.synapse_id.nil?
mapping.mappable = Synapse.find_by(id: mapping.synapse_id)
else
mapping.mappable = Topic.find_by(id: mapping.topic_id)
end
if mapping.mappable.nil?
mapping.delete
else
mapping.save
end
end
end
def down
remove_index :mappings, [:mappable_id, :mappable_type]
remove_column :mappings, :mappable_id, :integer
remove_column :mappings, :mappable_type, :string
end
end