1 files changed, 33 insertions, 0 deletions
diff --git a/app/finders/merge_requests/oldest_per_commit_finder.rb b/app/finders/merge_requests/oldest_per_commit_finder.rb
new file mode 100644
index 00000000000..f50db43d7d2
--- /dev/null
+++ b/app/finders/merge_requests/oldest_per_commit_finder.rb
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module MergeRequests
+  # OldestPerCommitFinder is used to retrieve the oldest merge requests for
+  # every given commit, grouped per commit SHA.
+  #
+  # This finder is useful when you need to efficiently retrieve the first/oldest
+  # merge requests for multiple commits, and you want to do so in batches;
+  # instead of running a query for every commit.
+  class OldestPerCommitFinder
+    def initialize(project)
+      @project = project
+    end
+
+    # Returns a Hash that maps a commit ID to the oldest merge request that
+    # introduced that commit.
+    def execute(commits)
+      id_rows = MergeRequestDiffCommit
+        .oldest_merge_request_id_per_commit(@project.id, commits.map(&:id))
+
+      mrs = MergeRequest
+        .preload_target_project
+        .id_in(id_rows.map { |r| r[:merge_request_id] })
+        .index_by(&:id)
+
+      id_rows.each_with_object({}) do |row, hash|
+        if (mr = mrs[row[:merge_request_id]])
+          hash[row[:sha]] = mr
+        end
+      end
+    end
+  end
+end