Cleanup after adding MR diff's commit_count (try 2)

* processes any pending records which are not migrated yet
* bumps import_export version because of new commits_count attribute
* removes commits_count fallback method

app/models/merge_request_diff.rb

@@ -197,10 +197,6 @@ class MergeRequestDiff < ActiveRecord::Base
     CompareService.new(project, head_commit_sha).execute(project, sha, straight: true)
   end
 
-  def commits_count
-    super || merge_request_diff_commits.size
-  end
-
   private
 
   def create_merge_request_diff_files(diffs)

db/migrate/20180425131009_assure_commits_count_for_merge_request_diff.rb

@@ -0,0 +1,27 @@
+class AssureCommitsCountForMergeRequestDiff < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  class MergeRequestDiff < ActiveRecord::Base
+    self.table_name = 'merge_request_diffs'
+
+    include ::EachBatch
+  end
+
+  def up
+    Gitlab::BackgroundMigration.steal('AddMergeRequestDiffCommitsCount')
+
+    MergeRequestDiff.where(commits_count: nil).each_batch(of: 50) do |batch|
+      range = batch.pluck('MIN(id)', 'MAX(id)').first
+
+      Gitlab::BackgroundMigration::AddMergeRequestDiffCommitsCount.new.perform(*range)
+    end
+  end
+
+  def down
+    # noop
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20180418053107) do
+ActiveRecord::Schema.define(version: 20180425131009) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"

doc/user/project/settings/import_export.md

@@ -31,7 +31,8 @@ with all their related data and be moved into a new GitLab instance.
 
 | GitLab version   | Import/Export version |
 | ---------------- | --------------------- |
-| 10.4 to current  | 0.2.2                 |
+| 10.8 to current  | 0.2.3                 |
+| 10.4             | 0.2.2                 |
 | 10.3             | 0.2.1                 |
 | 10.0             | 0.2.0                 |
 | 9.4.0            | 0.1.8                 |

lib/gitlab/import_export.rb

@@ -3,7 +3,7 @@ module Gitlab
     extend self
 
     # For every version update, the version history in import_export.md has to be kept up to date.
-    VERSION = '0.2.2'.freeze
+    VERSION = '0.2.3'.freeze
     FILENAME_LIMIT = 50
 
     def export_path(relative_path:)

spec/migrations/assure_commits_count_for_merge_request_diff_spec.rb

@@ -0,0 +1,32 @@
+require 'spec_helper'
+require Rails.root.join('db', 'migrate', '20180425131009_assure_commits_count_for_merge_request_diff.rb')
+
+describe AssureCommitsCountForMergeRequestDiff, :migration, :sidekiq, :redis do
+  let(:migration) { spy('migration') }
+
+  before do
+    allow(Gitlab::BackgroundMigration::AddMergeRequestDiffCommitsCount)
+      .to receive(:new).and_return(migration)
+  end
+
+  context 'when there are still unmigrated commit_counts afterwards' do
+    let(:namespaces) { table('namespaces') }
+    let(:projects) { table('projects') }
+    let(:merge_requests) { table('merge_requests') }
+    let(:diffs) { table('merge_request_diffs') }
+
+    before do
+      namespace = namespaces.create(name: 'foo', path: 'foo')
+      project = projects.create!(namespace_id: namespace.id)
+      merge_request = merge_requests.create!(source_branch: 'x', target_branch: 'y', target_project_id: project.id)
+      diffs.create!(commits_count: nil, merge_request_id: merge_request.id)
+      diffs.create!(commits_count: nil, merge_request_id: merge_request.id)
+    end
+
+    it 'migrates commit_counts sequentially in batches' do
+      migrate!
+
+      expect(migration).to have_received(:perform).once
+    end
+  end
+end