1 files changed, 156 insertions, 0 deletions
diff --git a/lib/gitlab/background_migration/fix_merge_request_diff_commit_users.rb b/lib/gitlab/background_migration/fix_merge_request_diff_commit_users.rb
new file mode 100644
index 00000000000..ea3e56cb14a
--- /dev/null
+++ b/lib/gitlab/background_migration/fix_merge_request_diff_commit_users.rb
@@ -0,0 +1,156 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module BackgroundMigration
+    # Background migration for fixing merge_request_diff_commit rows that don't
+    # have committer/author details due to
+    # https://gitlab.com/gitlab-org/gitlab/-/issues/344080.
+    #
+    # This migration acts on a single project and corrects its data. Because
+    # this process needs Git/Gitaly access, and duplicating all that code is far
+    # too much, this migration relies on global models such as Project,
+    # MergeRequest, etc.
+    # rubocop: disable Metrics/ClassLength
+    class FixMergeRequestDiffCommitUsers
+      BATCH_SIZE = 100
+
+      def initialize
+        @commits = {}
+        @users = {}
+      end
+
+      def perform(project_id)
+        if (project = ::Project.find_by_id(project_id))
+          process(project)
+        end
+
+        ::Gitlab::Database::BackgroundMigrationJob.mark_all_as_succeeded(
+          'FixMergeRequestDiffCommitUsers',
+          [project_id]
+        )
+
+        schedule_next_job
+      end
+
+      def process(project)
+        # Loading everything using one big query may result in timeouts (e.g.
+        # for projects the size of gitlab-org/gitlab). So instead we query
+        # data on a per merge request basis.
+        project.merge_requests.each_batch(column: :iid) do |mrs|
+          mrs.ids.each do |mr_id|
+            each_row_to_check(mr_id) do |commit|
+              update_commit(project, commit)
+            end
+          end
+        end
+      end
+
+      def each_row_to_check(merge_request_id, &block)
+        columns = %w[merge_request_diff_id relative_order].map do |col|
+          Pagination::Keyset::ColumnOrderDefinition.new(
+            attribute_name: col,
+            order_expression: MergeRequestDiffCommit.arel_table[col.to_sym].asc,
+            nullable: :not_nullable,
+            distinct: false
+          )
+        end
+
+        order = Pagination::Keyset::Order.build(columns)
+        scope = MergeRequestDiffCommit
+          .joins(:merge_request_diff)
+          .where(merge_request_diffs: { merge_request_id: merge_request_id })
+          .where('commit_author_id IS NULL OR committer_id IS NULL')
+          .order(order)
+
+        Pagination::Keyset::Iterator
+          .new(scope: scope, use_union_optimization: true)
+          .each_batch(of: BATCH_SIZE) do |rows|
+            rows
+              .select([
+                :merge_request_diff_id,
+                :relative_order,
+                :sha,
+                :committer_id,
+                :commit_author_id
+              ])
+              .each(&block)
+          end
+      end
+
+      # rubocop: disable Metrics/AbcSize
+      def update_commit(project, row)
+        commit = find_commit(project, row.sha)
+        updates = []
+
+        unless row.commit_author_id
+          author_id = find_or_create_user(commit, :author_name, :author_email)
+
+          updates << [arel_table[:commit_author_id], author_id] if author_id
+        end
+
+        unless row.committer_id
+          committer_id =
+            find_or_create_user(commit, :committer_name, :committer_email)
+
+          updates << [arel_table[:committer_id], committer_id] if committer_id
+        end
+
+        return if updates.empty?
+
+        update = Arel::UpdateManager
+          .new
+          .table(MergeRequestDiffCommit.arel_table)
+          .where(matches_row(row))
+          .set(updates)
+          .to_sql
+
+        MergeRequestDiffCommit.connection.execute(update)
+      end
+      # rubocop: enable Metrics/AbcSize
+
+      def schedule_next_job
+        job = Database::BackgroundMigrationJob
+          .for_migration_class('FixMergeRequestDiffCommitUsers')
+          .pending
+          .first
+
+        return unless job
+
+        BackgroundMigrationWorker.perform_in(
+          2.minutes,
+          'FixMergeRequestDiffCommitUsers',
+          job.arguments
+        )
+      end
+
+      def find_commit(project, sha)
+        @commits[sha] ||= (project.commit(sha)&.to_hash || {})
+      end
+
+      def find_or_create_user(commit, name_field, email_field)
+        name = commit[name_field]
+        email = commit[email_field]
+
+        return unless name && email
+
+        @users[[name, email]] ||=
+          MergeRequest::DiffCommitUser.find_or_create(name, email).id
+      end
+
+      def matches_row(row)
+        primary_key = Arel::Nodes::Grouping
+          .new([arel_table[:merge_request_diff_id], arel_table[:relative_order]])
+
+        primary_val = Arel::Nodes::Grouping
+          .new([row.merge_request_diff_id, row.relative_order])
+
+        primary_key.eq(primary_val)
+      end
+
+      def arel_table
+        MergeRequestDiffCommit.arel_table
+      end
+    end
+    # rubocop: enable Metrics/ClassLength
+  end
+end