Add Rake task to migrate milestone data to new tables

lib/tasks/migrate_milestones_and_statuses.rake

@@ -0,0 +1,92 @@
+namespace :milestones do
+
+  def generate_table_migration_sql(new_table:, old_table:, columns:)
+    from_cols = ['id', *columns.keys]
+    to_cols   = ['id', *columns.values]
+    <<~SQL
+      INSERT INTO #{new_table} (#{to_cols.join(', ')})
+      SELECT #{from_cols.join(', ')} FROM #{old_table};
+    SQL
+  end
+
+  def migrate_table!(new_table:, old_table:, columns:)
+    puts "Migrating data from '#{old_table}' to '#{new_table}'..."
+    result = ActiveRecord::Base.connection.execute(
+      generate_table_migration_sql(old_table: old_table,
+                                   new_table: new_table,
+                                   columns:   columns)
+
+    )
+    puts "#{result.cmd_tuples} rows affected"
+  end
+
+  def populate_column!(table:, column:, value:)
+    puts "Populating column '#{column}' from table '#{table}' with '#{value}'..."
+    result = ActiveRecord::Base.connection.execute(
+      "UPDATE #{table} SET #{column} = '#{value}';"
+    )
+    puts "#{result.cmd_tuples} rows affected"
+  end
+
+  def count_rows(table)
+    ActiveRecord::Base.connection.query("SELECT COUNT(*) FROM #{table};")[0][0].to_i
+  end
+
+  desc "Migrate milestones and milestone status data after making the model polymorphic"
+  task migrate: :environment do
+    # This script copies all milestone-related data from the old tables to
+    # the new ones (preserving all primary keys). All 3 of the new tables
+    # must be empty.
+    #
+    # To clear the new tables to test this script:
+    #
+    #   DELETE FROM milestone_statuses;
+    #   DELETE FROM milestones;
+    #   DELETE FROM milestone_translations;
+    #
+
+    start = Time.now
+
+    ActiveRecord::Base.transaction do
+      migrate_table! old_table: 'budget_investment_statuses',
+                     new_table: 'milestone_statuses',
+                     columns: {'name'        => 'name',
+                               'description' => 'description',
+                               'hidden_at'   => 'hidden_at',
+                               'created_at'  => 'created_at',
+                               'updated_at'  => 'updated_at'}
+
+      migrate_table! old_table: 'budget_investment_milestones',
+                     new_table: 'milestones',
+                     columns: {'investment_id' => 'milestoneable_id',
+                               'title'         => 'title',
+                               'description'   => 'description',
+                               'created_at'    => 'created_at',
+                               'updated_at'    => 'updated_at',
+                               'publication_date' => 'publication_date',
+                               'status_id'     => 'status_id'}
+
+      populate_column! table:  'milestones',
+                       column: 'milestoneable_type',
+                       value:  'Budget::Investment'
+
+      migrate_table! old_table: 'budget_investment_milestone_translations',
+                     new_table: 'milestone_translations',
+                     columns: {'budget_investment_milestone_id' => 'milestone_id',
+                               'locale'      => 'locale',
+                               'created_at'  => 'created_at',
+                               'updated_at'  => 'updated_at',
+                               'title'       => 'title',
+                               'description' => 'description'}
+
+      puts "Verifying that all rows were copied..."
+      unless count_rows('milestones') == count_rows('budget_investment_milestones') &&
+             count_rows('milestone_statuses') == count_rows('budget_investment_statuses') &&
+             count_rows('milestone_translations') == count_rows('budget_investment_milestone_translations')
+        raise "Number of rows of old and new tables do not match! Rolling back transaction..."
+      end
+    end
+
+    puts "Finished in %.3f seconds" % (Time.now - start)
+  end
+end

spec/lib/tasks/milestones_spec.rb

@@ -0,0 +1,121 @@
+require "rails_helper"
+require "rake"
+
+describe "Milestones tasks" do
+  before do
+    Rake.application.rake_require "tasks/migrate_milestones_and_statuses"
+    Rake::Task.define_task(:environment)
+  end
+
+  describe "#migrate" do
+    let :run_rake_task do
+      Rake::Task["milestones:migrate"].reenable
+      Rake.application.invoke_task "milestones:migrate"
+    end
+
+    let!(:investment) { create(:budget_investment) }
+
+    before do
+      ActiveRecord::Base.connection.execute(
+        "INSERT INTO budget_investment_statuses " +
+        "(name, description, hidden_at, created_at, updated_at) " +
+        "VALUES ('open', 'Good', NULL, '#{Time.current - 1.day}', '#{Time.current}');"
+      )
+
+      status_id = ActiveRecord::Base.connection.execute(
+        "SELECT MAX(id) FROM budget_investment_statuses;"
+      ).to_a.first["max"]
+
+      milestone_attributes = {
+        investment_id:     investment.id,
+        title:             "First",
+        description:       "Interesting",
+        publication_date:  Date.yesterday,
+        status_id:         status_id,
+        created_at:        Time.current - 1.day,
+        updated_at:        Time.current
+      }
+
+      ActiveRecord::Base.connection.execute(
+        "INSERT INTO budget_investment_milestones " +
+        "(#{milestone_attributes.keys.join(", ")}) " +
+        "VALUES (#{milestone_attributes.values.map { |value| "'#{value}'"}.join(", ")})"
+      )
+    end
+
+    it "migrates statuses" do
+      run_rake_task
+
+      expect(Milestone::Status.count).to be 1
+
+      status = Milestone::Status.first
+      expect(status.name).to eq "open"
+      expect(status.description).to eq "Good"
+      expect(status.hidden_at).to be nil
+      expect(status.created_at.to_date).to eq Date.yesterday
+      expect(status.updated_at.to_date).to eq Date.today
+    end
+
+    it "migrates milestones" do
+      run_rake_task
+
+      expect(Milestone.count).to be 1
+
+      milestone = Milestone.first
+      expect(milestone.milestoneable_id).to eq investment.id
+      expect(milestone.milestoneable_type).to eq "Budget::Investment"
+      expect(milestone.title).to eq "First"
+      expect(milestone.description).to eq "Interesting"
+      expect(milestone.publication_date).to eq Date.yesterday
+      expect(milestone.status_id).to eq Milestone::Status.first.id
+      expect(milestone.created_at.to_date).to eq Date.yesterday
+      expect(milestone.updated_at.to_date).to eq Date.today
+    end
+
+    context "Statuses had been deleted" do
+      before do
+        ActiveRecord::Base.connection.execute(
+          "INSERT INTO budget_investment_statuses " +
+          "(name, description, hidden_at, created_at, updated_at) " +
+          "VALUES ('deleted', 'Del', NULL, '#{Time.current - 1.day}', '#{Time.current}');"
+        )
+
+        ActiveRecord::Base.connection.execute(
+          "DELETE FROM budget_investment_statuses WHERE name='deleted'"
+        )
+
+        ActiveRecord::Base.connection.execute(
+          "INSERT INTO budget_investment_statuses " +
+          "(name, description, hidden_at, created_at, updated_at) " +
+          "VALUES ('new', 'New', NULL, '#{Time.current - 1.day}', '#{Time.current}');"
+        )
+
+        status_id = ActiveRecord::Base.connection.execute(
+          "SELECT MAX(id) FROM budget_investment_statuses;"
+        ).to_a.first["max"]
+
+        milestone_attributes = {
+          investment_id:     investment.id,
+          title:             "Last",
+          description:       "Different",
+          publication_date:  Date.yesterday,
+          status_id:         status_id,
+          created_at:        Time.current - 1.day,
+          updated_at:        Time.current
+        }
+
+        ActiveRecord::Base.connection.execute(
+          "INSERT INTO budget_investment_milestones " +
+          "(#{milestone_attributes.keys.join(", ")}) " +
+          "VALUES (#{milestone_attributes.values.map { |value| "'#{value}'"}.join(", ")})"
+        )
+      end
+
+      it "migrates the status id correctly" do
+        run_rake_task
+
+        expect(Milestone.last.status_id).to eq Milestone::Status.last.id
+      end
+    end
+  end
+end