Remove background migration from 20200312134637

This migration is deleted because there is no foreign key for
deployments.environment_id and this caused a failure upgrading
deployments_merge_requests.environment_id

Details on the following issues:
 * https://gitlab.com/gitlab-org/gitlab/-/issues/217191
 * https://gitlab.com/gitlab-org/gitlab/-/issues/26229

changelogs/unreleased/ac-backfill-environment_id-on-deployment_merge_requests.yml

----
-title: backfill environment_id on deployment_merge_requests
-merge_request: 27219
-author:
-type: other

db/post_migrate/20200312134637_backfill_environment_id_on_deployment_merge_requests.rb

@@ -4,46 +4,19 @@ class BackfillEnvironmentIdOnDeploymentMergeRequests < ActiveRecord::Migration[6
   include Gitlab::Database::MigrationHelpers
 
   DOWNTIME = false
-  BATCH_SIZE = 400
-  DELAY = 1.minute
 
   disable_ddl_transaction!
 
   def up
-    max_mr_id = DeploymentMergeRequest
-      .select(:merge_request_id)
-      .distinct
-      .order(merge_request_id: :desc)
-      .limit(1)
-      .pluck(:merge_request_id)
-      .first || 0
-
-    last_mr_id = 0
-    step = 0
-
-    while last_mr_id < max_mr_id
-      stop =
-        DeploymentMergeRequest
-          .select(:merge_request_id)
-          .distinct
-          .where('merge_request_id > ?', last_mr_id)
-          .order(:merge_request_id)
-          .offset(BATCH_SIZE)
-          .limit(1)
-          .pluck(:merge_request_id)
-          .first
-
-      stop ||= max_mr_id
-
-      migrate_in(
-        step * DELAY,
-        'BackfillEnvironmentIdDeploymentMergeRequests',
-        [last_mr_id + 1, stop]
-      )
+    # no-op
 
-      last_mr_id = stop
-      step += 1
-    end
+    # this migration is deleted because there is no foreign key for
+    # deployments.environment_id and this caused a failure upgrading
+    # deployments_merge_requests.environment_id
+    #
+    # Details on the following issues:
+    #  * https://gitlab.com/gitlab-org/gitlab/-/issues/217191
+    #  * https://gitlab.com/gitlab-org/gitlab/-/issues/26229
   end
 
   def down

lib/gitlab/background_migration/backfill_environment_id_deployment_merge_requests.rb

@@ -5,7 +5,14 @@ module Gitlab
     # BackfillEnvironmentIdDeploymentMergeRequests deletes duplicates
     # from deployment_merge_requests table and backfills environment_id
     class BackfillEnvironmentIdDeploymentMergeRequests
-      def perform(start_mr_id, stop_mr_id)
+      def perform(_start_mr_id, _stop_mr_id)
+        # no-op
+
+        # Background migration removed due to
+        # https://gitlab.com/gitlab-org/gitlab/-/issues/217191
+      end
+
+      def backfill_range(start_mr_id, stop_mr_id)
         start_mr_id = Integer(start_mr_id)
         stop_mr_id  = Integer(stop_mr_id)
 

spec/lib/gitlab/background_migration/backfill_environment_id_deployment_merge_requests_spec.rb

@@ -32,7 +32,7 @@ describe Gitlab::BackgroundMigration::BackfillEnvironmentIdDeploymentMergeReques
 
     expect(deployment_merge_requests.where(environment_id: nil).count).to eq(3)
 
-    migration.perform(1, mr.id)
+    migration.backfill_range(1, mr.id)
 
     expect(deployment_merge_requests.where(environment_id: nil).count).to be_zero
     expect(deployment_merge_requests.count).to eq(2)

spec/migrations/backfill_environment_id_on_deployment_merge_requests_spec.rb

-# frozen_string_literal: true
-
-require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20200312134637_backfill_environment_id_on_deployment_merge_requests.rb')
-
-describe BackfillEnvironmentIdOnDeploymentMergeRequests do
-  let(:environments)              { table(:environments) }
-  let(:merge_requests)            { table(:merge_requests) }
-  let(:deployments)               { table(:deployments) }
-  let(:deployment_merge_requests) { table(:deployment_merge_requests) }
-  let(:namespaces)                { table(:namespaces) }
-  let(:projects)                  { table(:projects) }
-
-  let(:migration_worker) { double('BackgroundMigrationWorker') }
-
-  before do
-    stub_const('BackgroundMigrationWorker', migration_worker)
-  end
-
-  it 'schedules nothing when there are no entries' do
-    expect(migration_worker).not_to receive(:perform_in)
-
-    migrate!
-  end
-
-  it 'batches the workload' do
-    stub_const("#{described_class.name}::BATCH_SIZE", 10)
-
-    namespace = namespaces.create!(name: 'foo', path: 'foo')
-    project = projects.create!(namespace_id: namespace.id)
-
-    environment = environments.create!(project_id: project.id, name: 'staging', slug: 'staging')
-
-    # Batching is based on DeploymentMergeRequest.merge_request_id, in order to test it
-    # we must generate more than described_class::BATCH_SIZE merge requests, deployments,
-    # and deployment_merge_requests entries
-    entries = 13
-    expect(entries).to be > described_class::BATCH_SIZE
-
-    # merge requests and deployments bulk generation
-    mrs_params = []
-    deployments_params = []
-    entries.times do |i|
-      mrs_params << { source_branch: 'x', target_branch: 'master', target_project_id: project.id }
-
-      deployments_params << { environment_id: environment.id, iid: i + 1, project_id: project.id, ref: 'master', tag: false, sha: '123abcdef', status: 1 }
-    end
-
-    all_mrs = merge_requests.insert_all(mrs_params)
-    all_deployments = deployments.insert_all(deployments_params)
-
-    # deployment_merge_requests bulk generation
-    dmr_params = []
-    entries.times do |index|
-      mr_id = all_mrs.rows[index].first
-      deployment_id = all_deployments.rows[index].first
-
-      dmr_params << { deployment_id: deployment_id, merge_request_id: mr_id }
-    end
-
-    deployment_merge_requests.insert_all(dmr_params)
-
-    first_batch_limit = dmr_params[described_class::BATCH_SIZE][:merge_request_id]
-    second_batch_limit = dmr_params.last[:merge_request_id]
-
-    expect(migration_worker).to receive(:perform_in)
-                                  .with(
-                                    0,
-                                    'BackfillEnvironmentIdDeploymentMergeRequests',
-                                    [1, first_batch_limit]
-                                  )
-    expect(migration_worker).to receive(:perform_in)
-                                  .with(
-                                    described_class::DELAY,
-                                    'BackfillEnvironmentIdDeploymentMergeRequests',
-                                    [first_batch_limit + 1, second_batch_limit]
-                                  )
-
-    migrate!
-  end
-end