Add update generator and new migration

To be used as `bin/rails solid_queue:update` to copy new migrations.

The new migration links claimed executions to processes with
`process_name`, and replaces the unique index on processes on
`supervisor_id, name` with just `name`, as we'll want the name to
uniquely identify a process because we'll rely on that to release
claimed executions, independently from the supervisor. Even though it
was really unlikely to have a collision on name because these are set
randomly with `SecureRandom.hex(10)`, in this way we guarantee it.

fix

Author: rosa

lib/generators/solid_queue/update/templates/db/link_claimed_executions_with_processes_through_name.rb

@@ -0,0 +1,30 @@
+class LinkClaimedExecutionsWithProcessesThroughName < ActiveRecord::Migration[<%= ActiveRecord::VERSION::STRING.to_f %>]
+  def up
+    unless connection.column_exists?(:solid_queue_claimed_executions, :process_name)
+      add_column :solid_queue_claimed_executions, :process_name, :string
+      add_index :solid_queue_claimed_executions, :process_name
+    end
+
+    unless connection.index_exists?(:solid_queue_processes, :name)
+      add_index :solid_queue_processes, :name, unique: true
+    end
+
+    if connection.index_exists?(:solid_queue_processes, [ :name, :supervisor_id ])
+      remove_index :solid_queue_processes, [ :name, :supervisor_id ]
+    end
+  end
+
+  def down
+    if connection.column_exists?(:solid_queue_claimed_executions, :process_name)
+      remove_column :solid_queue_claimed_executions, :process_name
+    end
+
+    if connection.index_exists?(:solid_queue_processes, :name)
+      remove_index :solid_queue_processes, :name
+    end
+
+    unless connection.index_exists?(:solid_queue_processes, [ :name, :supervisor_id ])
+      add_index :solid_queue_processes, [ :name, :supervisor_id ], unique: true
+    end
+  end
+end

lib/generators/solid_queue/update/update_generator.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "rails/generators/active_record"
+
+class SolidQueue::UpdateGenerator < Rails::Generators::Base
+  include ActiveRecord::Generators::Migration
+
+  source_root File.expand_path("templates", __dir__)
+
+  class_option :database, type: :string, aliases: %i[ --db ], default: "queue",
+    desc: "The database that Solid Queue uses. Defaults to `queue`"
+
+  def copy_new_migrations
+    template_dir = Dir.new(File.join(self.class.source_root, "db"))
+
+    template_dir.each_child do |migration_file|
+      migration_template File.join("db", migration_file), File.join(db_migrate_path, migration_file), skip: true
+    end
+  end
+end

lib/solid_queue/tasks.rb

@@ -4,7 +4,12 @@
     Rails::Command.invoke :generate, [ "solid_queue:install" ]
   end
 
-  desc "start solid_queue supervisor to dispatch and process jobs"
+  desc "Update Solid Queue"
+  task :update do
+    Rails::Command.invoke :generate, [ "solid_queue:update" ]
+  end
+
+  desc "Start Solid Queue supervisor to dispatch and process jobs"
   task start: :environment do
     SolidQueue::Supervisor.start
   end