Drop all Postgres sequences during backup restore

lib/backup/database.rb

@@ -34,6 +34,7 @@ module Backup
         # Drop all tables because PostgreSQL DB dumps do not contain DROP TABLE
         # statements like MySQL.
         Rake::Task["gitlab:db:drop_all_tables"].invoke
+        Rake::Task["gitlab:db:drop_all_postgres_sequences"].invoke
         pg_env
         system('psql', config['database'], '-f', db_file_name)
       end

lib/tasks/gitlab/db/drop_all_postgres_sequences.rake

+namespace :gitlab do
+  namespace :db do
+    task drop_all_postgres_sequences: :environment do
+      connection = ActiveRecord::Base.connection
+      connection.execute("SELECT c.relname FROM pg_class c WHERE c.relkind = 'S';").each do |sequence|
+        connection.execute("DROP SEQUENCE #{sequence['relname']}")
+      end
+    end
+  end
+end