Backup visualizations before deletion

NEWS.md

@@ -29,6 +29,7 @@ Development
 * Delete unused DataImport methods [#15833](https://github.com/CartoDB/cartodb/pull/15833)
 * Fix missing LoggerHelper in CartoDB::LayerModule::Presenter [#15829](https://github.com/CartoDB/cartodb/pull/15829)
 * Release Data Observatory subscriptions [#15834](https://github.com/CartoDB/cartodb/pull/15834)
+* Fix map backups when deleting tables via Ghost Tables [#15832](https://github.com/CartoDB/cartodb/pull/15832)
 
 4.41.1 (2020-09-03)
 -------------------

app/models/table.rb

@@ -46,6 +46,7 @@ class Table
   def_delegators :relator, *CartoDB::TableRelator::INTERFACE
   def_delegators :@user_table, *::UserTable::INTERFACE
 
+  attr_accessor :user_table
 
   def initialize(args = {})
     if args[:user_table].nil?
@@ -1215,6 +1216,10 @@ class Table
     self.class.sanitize_columns(table_name, column_sanitization_version, options)
   end
 
+  def visualizations
+    Carto::Visualization.where(id: user_table.affected_visualizations.map(&:id))
+  end
+
   private
 
   def valid_cartodb_id_candidate?(col_name)

lib/carto/ghost_tables_manager.rb

@@ -263,6 +263,8 @@ module Carto
       return unless user_table_to_drop # The table has already been deleted
 
       table_to_drop = ::Table.new(user_table: user_table_to_drop)
+
+      table_to_drop.visualizations.map(&:backup_visualization)
       table_to_drop.keep_user_database_table = true
       table_to_drop.destroy
     rescue StandardError => exception

spec/lib/carto/ghost_tables_manager_spec.rb

@@ -15,6 +15,8 @@ module Carto
       Rails.logger.expects(:error).never
     end
 
+    after { Carto::User.destroy_all }
+
     def run_in_user_database(query)
       sequel_user.in_database.run(query)
     end
@@ -427,5 +429,16 @@ module Carto
       user.tables.count.should eq 0
       ghost_tables_manager.instance_eval { fetch_user_tables_synced_with_db? }.should be_true
     end
+
+    it 'should backup visualizations before dropping a table' do
+      user_table = create(:carto_user_table, :full, user: user)
+
+      expect(Carto::VisualizationBackup.count).to eq(0)
+
+      run_in_user_database("ALTER TABLE #{user_table.name} DROP COLUMN cartodb_id")
+      ghost_tables_manager.link_ghost_tables_synchronously
+
+      expect(Carto::VisualizationBackup.count).to eq(1)
+    end
   end
 end