Batchload blobs for diff generation

After installing a new gem, batch-loader, a construct can be used to
queue data to be fetched in bulk. The gem was also introduced in both
gitlab-org/gitlab-ce!14680 and gitlab-org/gitlab-ce!14846, but those mrs
are not merged yet.

For the generation of diffs, both the old blob and the new blob need to
be loaded. This for every file in the diff, too. Now we collect all
these so we do 1 fetch. Three `.allow_n_plus_1_calls` have been removed,
which I expect to be valid, but this needs to be confirmed by a full CI
run.

Possibly closes:
- https://gitlab.com/gitlab-org/gitlab-ce/issues/37445
- https://gitlab.com/gitlab-org/gitlab-ce/issues/37599
- https://gitlab.com/gitlab-org/gitlab-ce/issues/37431

1 files changed, 16 insertions, 1 deletions

diff --git a/app/models/blob.rb b/app/models/blob.rb
index ad0bc2e2ead..29e762724e3 100644
--- a/app/models/blob.rb
+++ b/app/models/blob.rb
@@ -76,12 +76,24 @@ class Blob < SimpleDelegator
     new(blob, project)
   end
 
+  def self.lazy(project, commit_id, path)
+    BatchLoader.for(commit_id: commit_id, path: path).batch do |items, loader|
+      project.repository.blobs_at(items.map(&:values)).each do |blob|
+        loader.call({ commit_id: blob.commit_id, path: blob.path }, blob) if blob
+      end
+    end
+  end
+
   def initialize(blob, project = nil)
     @project = project
 
     super(blob)
   end
 
+  def inspect
+    "#<#{self.class.name} oid:#{id[0..8]} commit:#{commit_id[0..8]} path:#{path}>"
+  end
+
   # Returns the data of the blob.
   #
   # If the blob is a text based blob the content is converted to UTF-8 and any
@@ -95,7 +107,10 @@ class Blob < SimpleDelegator
   end
 
   def load_all_data!
-    super(project.repository) if project
+    # Endpoint needed: gitlab-org/gitaly#756
+    Gitlab::GitalyClient.allow_n_plus_1_calls do
+      super(project.repository) if project
+    end
   end
 
   def no_highlighting?