Add background migration to fill pipeline source

lib/gitlab/background_migration/populate_external_pipeline_source.rb

+# frozen_string_literal: true
+# rubocop:disable Style/Documentation
+
+module Gitlab
+  module BackgroundMigration
+    class PopulateExternalPipelineSource
+      module Migratable
+        class Pipeline < ActiveRecord::Base
+          self.table_name = 'ci_pipelines'
+
+          def self.sources
+            {
+              unknown: nil,
+              push: 1,
+              web: 2,
+              trigger: 3,
+              schedule: 4,
+              api: 5,
+              external: 6
+            }
+          end
+        end
+
+        class CommitStatus < ActiveRecord::Base
+          self.table_name = 'ci_builds'
+          self.inheritance_column = :_type_disabled
+        end
+
+        class Build < CommitStatus
+        end
+
+        class GenericCommitStatus < CommitStatus
+        end
+      end
+
+      def perform(start_id, stop_id)
+        external_pipelines(start_id, stop_id).each do |pipeline|
+          pipeline.update_attribute(:source, Migratable::Pipeline.sources[:external])
+        end
+      end
+
+      private
+
+      def external_pipelines(start_id, stop_id)
+        Migratable::Pipeline.where(id: (start_id..stop_id))
+          .where(
+            'EXISTS (?) AND NOT EXISTS (?)',
+            Migratable::GenericCommitStatus.where("type='CommitStatus'").where('ci_builds.commit_id=ci_pipelines.id').select(1),
+            Migratable::Build.where("type='Ci::Build'").where('ci_builds.commit_id=ci_pipelines.id').select(1)
+          )
+      end
+    end
+  end
+end

spec/lib/gitlab/background_migration/populate_external_pipeline_source_spec.rb

+require 'spec_helper'
+
+describe Gitlab::BackgroundMigration::PopulateExternalPipelineSource, :migration, schema: 20180916011959 do
+  let(:migration) { described_class.new }
+  let(:projects) { table(:projects) }
+  let(:pipelines) { table(:ci_pipelines) }
+  let(:statuses) { table(:ci_builds) }
+  let(:builds) { table(:ci_builds) }
+
+  let!(:internal_pipeline) { pipelines.create(id: 1, source: described_class::Migratable::Pipeline.sources[:web]) }
+  let!(:external_pipeline) { pipelines.create(id: 2, source: nil) }
+  let!(:second_external_pipeline) { pipelines.create(id: 3, source: nil) }
+  let!(:status) { statuses.create(id: 1, commit_id: 2, type: 'CommitStatus') }
+  let!(:build) { builds.create(id: 2, commit_id: 1, type: 'Ci::Build') }
+
+  subject { migration.perform(1, 2) }
+
+  it 'populates the pipeline source' do
+    subject
+
+    expect(external_pipeline.reload.source).to eq(described_class::Migratable::Pipeline.sources[:external])
+  end
+
+  it 'only processes a single batch of links at a time' do
+    subject
+
+    expect(second_external_pipeline.reload.source).to eq(nil)
+  end
+
+  it 'can be repeated without effect' do
+    subject
+
+    expect { subject }.not_to change { external_pipeline.reload.source }
+  end
+end