Set merge_request_diff_id on MR when creating

Once we migrate existing MRs to have this column, we will be able to get the latest diff for a single merge request more efficiently, and (more importantly) get all latest diffs for a collection of MRs efficiently.

Set merge_request_diff_id on MR when creating
4768a1e2 · Sean McGivern · d8299e32 · 4768a1e2 · 4768a1e2 · 4768a1e2
Commit 4768a1e2 authored Oct 26, 2017 by Sean McGivern
3 changed files
--- a/app/models/merge_request_diff.rb
+++ b/app/models/merge_request_diff.rb
@@ -48,6 +48,10 @@ class MergeRequestDiff < ActiveRecord::Base
  # Collect information about commits and diff from repository
  # and save it to the database as serialized data
  def save_git_content
+    MergeRequest
+      .where('id = ? AND COALESCE(latest_merge_request_diff_id, 0) < ?', self.merge_request_id, self.id)
+      .update_all(latest_merge_request_diff_id: self.id)
+
    ensure_commit_shas
    save_commits
    save_diffs

--- a/changelogs/unreleased/37631-add-a-merge_request_diff_id-column-to-merge_requests.yml
+++ b/changelogs/unreleased/37631-add-a-merge_request_diff_id-column-to-merge_requests.yml
 ---
-title: Make finding most recent merge request diffs more efficient
+title: Add a latest_merge_request_diff_id column to merge_requests
 merge_request: 15035
 author:
 type: performance
--- a/lib/gitlab/import_export/import_export.yml
+++ b/lib/gitlab/import_export/import_export.yml
@@ -113,7 +113,7 @@ excluded_attributes:
    - :milestone_id
    - :ref_fetched
    - :merge_jid
-    - :merge_request_diff_id
+    - :latest_merge_request_diff_id
  award_emoji:
    - :awardable_id
  statuses: