Ruby Migration generator for event_id index

RES Browser slowed down when displaying event overview.
It turned out it was because of "Event Streams" involving full table scan on
event_store_events_in_streams. Adding the index fixes the issue,
obviously.

Co-authored-by: Łukasz Reszke <[email protected]>

ruby_event_store-active_record/lib/ruby_event_store/active_record.rb

@@ -4,6 +4,7 @@
 require_relative "active_record/generators/rails_migration_generator"
 require_relative "active_record/generators/templates/template_directory"
 require_relative "active_record/generators/verify_data_type_for_adapter"
+require_relative "active_record/generators/event_id_index_migration_generator"
 require_relative "active_record/event"
 require_relative "active_record/with_default_models"
 require_relative "active_record/with_abstract_base_class"

ruby_event_store-active_record/lib/ruby_event_store/active_record/generators/event_id_index_migration_generator.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+module RubyEventStore
+  module ActiveRecord
+    class EventIdIndexMigrationGenerator
+      def call(migration_path)
+        path = build_path(migration_path)
+        write_to_file(path)
+        path
+      end
+
+      private
+
+      def absolute_path(path)
+        File.expand_path(path, __dir__)
+      end
+
+      def migration_code
+        migration_template.result_with_hash(migration_version: migration_version)
+      end
+
+      def migration_template
+        ERB.new(
+          File.read(
+            File.join(absolute_path("./templates"), "add_event_id_index_to_event_store_events_in_streams_template.erb")
+          )
+        )
+      end
+
+      def migration_version
+        ::ActiveRecord::Migration.current_version
+      end
+
+      def timestamp
+        Time.now.strftime("%Y%m%d%H%M%S")
+      end
+
+      def write_to_file(path)
+        File.write(path, migration_code)
+      end
+
+      def build_path(migration_path)
+        File.join("#{migration_path}", "#{timestamp}_add_event_id_index_to_event_store_events_in_streams.rb")
+      end
+    end
+  end
+end

ruby_event_store-active_record/lib/ruby_event_store/active_record/generators/templates/add_event_id_index_to_event_store_events_in_streams_template.erb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class AddEventIdIndexToEventStoreEventsInStreams < ActiveRecord::Migration[<%= migration_version %>]
+  def change
+    return if index_exists?(:event_store_events_in_streams, :event_id)
+
+    add_index :event_store_events_in_streams, [:event_id]
+  end
+end

ruby_event_store-active_record/spec/event_id_index_migration_generator_spec.rb

@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+require_relative "../../support/helpers/silence_stdout"
+
+module RubyEventStore
+  module ActiveRecord
+    ::RSpec.describe EventIdIndexMigrationGenerator do
+      around { |example| SilenceStdout.silence_stdout { example.run } }
+      around do |example|
+        begin
+          @dir = Dir.mktmpdir(nil, "./")
+          example.call
+        ensure
+          FileUtils.rm_r(@dir)
+          FileUtils.rm_f(["./20221130213700_add_event_id_index_to_event_store_events_in_streams.rb"])
+        end
+      end
+
+      before { allow(Time).to receive(:now).and_return(Time.new(2022, 11, 30, 21, 37, 00)) }
+
+      specify "it is created within specified directory" do
+        migration_generator(@dir)
+
+        expect(migration_exists?(@dir)).to be_truthy
+      end
+
+      specify "returns path to migration file" do
+        path = migration_generator(@dir)
+
+        expected_path = "#{@dir}/20221130213700_add_event_id_index_to_event_store_events_in_streams.rb"
+        expect(path).to match(expected_path)
+      end
+
+      specify "uses particular migration version" do
+        migration_generator(@dir)
+
+        expect(read_migration(@dir)).to include("ActiveRecord::Migration[#{::ActiveRecord::Migration.current_version}]")
+      end
+
+      specify "uses particular migration version for rails 6.0" do
+        skip unless ENV["BUNDLE_GEMFILE"]&.include?("rails_6_0")
+
+        migration_generator(@dir)
+
+        expect(read_migration(@dir)).to include("ActiveRecord::Migration[6.0]")
+      end
+
+      specify "uses particular migration version for rails 6.1" do
+        skip unless ENV["BUNDLE_GEMFILE"]&.include?("rails_6_1")
+
+        migration_generator(@dir)
+
+        expect(read_migration(@dir)).to include("ActiveRecord::Migration[6.1]")
+      end
+
+      private
+
+      def migration_generator(dir)
+        EventIdIndexMigrationGenerator.new.call(dir)
+      end
+
+      def migration_exists?(dir)
+        File.exist?("#{dir}/20221130213700_add_event_id_index_to_event_store_events_in_streams.rb")
+      end
+
+      def read_migration(dir)
+        File.read("#{dir}/20221130213700_add_event_id_index_to_event_store_events_in_streams.rb")
+      end
+    end
+  end
+end

ruby_event_store-active_record/spec/migration_test_spec.rb

@@ -57,9 +57,9 @@ module ActiveRecord
           Indexes:
               "event_store_events_in_streams_pkey" PRIMARY KEY, btree (id)
               "index_event_store_events_in_streams_on_created_at" btree (created_at)
+              "index_event_store_events_in_streams_on_event_id" btree (event_id)
               "index_event_store_events_in_streams_on_stream_and_event_id" UNIQUE, btree (stream, event_id)
               "index_event_store_events_in_streams_on_stream_and_position" UNIQUE, btree (stream, "position")
-              "index_event_store_events_in_streams_on_event_id" btree (event_id)
         SCHEMA
       end
 
@@ -101,8 +101,8 @@ module ActiveRecord
             PRIMARY KEY (`id`),
             UNIQUE KEY `index_event_store_events_in_streams_on_stream_and_event_id` (`stream`,`event_id`),
             UNIQUE KEY `index_event_store_events_in_streams_on_stream_and_position` (`stream`,`position`),
-            KEY `index_event_store_events_in_streams_on_event_id` (`event_id`),
-            KEY `index_event_store_events_in_streams_on_created_at` (`created_at`)
+            KEY `index_event_store_events_in_streams_on_created_at` (`created_at`),
+            KEY `index_event_store_events_in_streams_on_event_id` (`event_id`)
           ) ENGINE=InnoDB DEFAULT CHARSET=#{charset}#{collation}
         SCHEMA
       end