Backfill primary key migration for self-managed instances

See https://gitlab.com/gitlab-org/gitlab/-/issues/329511.

Changelog: added

db/post_migrate/20210520012430_backfill_pk_conversion_for_self_managed.rb

+# frozen_string_literal: true
+
+class BackfillPkConversionForSelfManaged < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  CONVERSIONS = [
+    { table: :events, columns: %i(id), sub_batch_size: 500 },
+    { table: :push_event_payloads, columns: %i(event_id), sub_batch_size: 2500, primary_key: :event_id },
+    { table: :ci_job_artifacts, columns: %i(id job_id), sub_batch_size: 2000 },
+    { table: :ci_sources_pipelines, columns: %i(source_job_id), sub_batch_size: 100 },
+    { table: :ci_build_needs, columns: %i(build_id), sub_batch_size: 1000 },
+    { table: :ci_builds, columns: %i(id stage_id), sub_batch_size: 250 },
+    { table: :ci_builds_runner_session, columns: %i(build_id), sub_batch_size: 5000 },
+    { table: :ci_build_trace_chunks, columns: %i(build_id), sub_batch_size: 1000 }
+  ]
+
+  def up
+    return unless should_run?
+
+    CONVERSIONS.each do |conversion|
+      backfill_conversion_of_integer_to_bigint(
+        conversion[:table], conversion[:columns],
+        sub_batch_size: conversion[:sub_batch_size], primary_key: conversion.fetch(:primary_key, :id)
+      )
+    end
+  end
+
+  def down
+    return unless should_run?
+
+    CONVERSIONS.each do |conversion|
+      revert_backfill_conversion_of_integer_to_bigint(
+        conversion[:table], conversion[:columns],
+        primary_key: conversion.fetch(:primary_key, :id)
+      )
+    end
+  end
+
+  private
+
+  def should_run?
+    !Gitlab.com?
+  end
+end

db/schema_migrations/20210520012430

+86b9f1c0f4288bf83e8b2d70b06b8951b7bcef0aa9324d9546471f6f094b014b
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