Improve performance of tree rendering in repositories with lots of items

Rails is slow to generate paths dynamically especially when called
hundreds/thousands of times. Also, rendering many partials hundreds
of times can be slower. This change reduces the number of partials
rendered and introduces two fast path methods to speed up path
generation.

10 files changed, 98 insertions, 46 deletions

diff --git a/app/helpers/icons_helper.rb b/app/helpers/icons_helper.rb
index 037004327b9..56ffd145f65 100644
--- a/app/helpers/icons_helper.rb
+++ b/app/helpers/icons_helper.rb
@@ -109,6 +109,8 @@ module IconsHelper
   def file_type_icon_class(type, mode, name)
     if type == 'folder'
       icon_class = 'folder'
+    elsif type == 'archive'
+      icon_class = 'archive'
     elsif mode == '120000'
       icon_class = 'share'
     else
diff --git a/app/helpers/tree_helper.rb b/app/helpers/tree_helper.rb
index 6d2da5699fb..78a11616d4c 100644
--- a/app/helpers/tree_helper.rb
+++ b/app/helpers/tree_helper.rb
@@ -31,11 +31,21 @@ module TreeHelper
   # mode - File unix mode
   # name - File name
   def tree_icon(type, mode, name)
-    icon("#{file_type_icon_class(type, mode, name)} fw")
+    icon([file_type_icon_class(type, mode, name), 'fw'])
   end
 
-  def tree_hex_class(content)
-    "file_#{hexdigest(content.name)}"
+  # Using Rails `*_path` methods can be slow, especially when generating
+  # many paths, as with a repository tree that has thousands of items.
+  def fast_project_blob_path(project, blob_path)
+    Addressable::URI.escape(
+      File.join(relative_url_root, project.path_with_namespace, 'blob', blob_path)
+    )
+  end
+
+  def fast_project_tree_path(project, tree_path)
+    Addressable::URI.escape(
+      File.join(relative_url_root, project.path_with_namespace, 'tree', tree_path)
+    )
   end
 
   # Simple shortcut to File.join
@@ -142,4 +152,8 @@ module TreeHelper
   def selected_branch
     @branch_name || tree_edit_branch
   end
+
+  def relative_url_root
+    Gitlab.config.gitlab.relative_url_root.presence || '/'
+  end
 end
diff --git a/app/views/projects/tree/_blob_item.html.haml b/app/views/projects/tree/_blob_item.html.haml
deleted file mode 100644
index f79f3af36d4..00000000000
--- a/app/views/projects/tree/_blob_item.html.haml
+++ /dev/null
@@ -1,12 +0,0 @@
-- is_lfs_blob = @lfs_blob_ids.include?(blob_item.id)
-%tr{ class: "tree-item #{tree_hex_class(blob_item)}" }
-  %td.tree-item-file-name
-    = tree_icon(type, blob_item.mode, blob_item.name)
-    - file_name = blob_item.name
-    = link_to project_blob_path(@project, tree_join(@id || @commit.id, blob_item.name)), class: 'str-truncated', title: file_name do
-      %span= file_name
-    - if is_lfs_blob
-      %span.badge.label-lfs.prepend-left-5 LFS
-  %td.d-none.d-sm-table-cell.tree-commit
-  %td.tree-time-ago.cgray.text-right
-    = render 'projects/tree/spinner'
diff --git a/app/views/projects/tree/_spinner.html.haml b/app/views/projects/tree/_spinner.html.haml
deleted file mode 100644
index b47ad0f41e4..00000000000
--- a/app/views/projects/tree/_spinner.html.haml
+++ /dev/null
@@ -1,3 +0,0 @@
-%span.log_loading.hide
-  %i.fa.fa-spinner.fa-spin
-  Loading commit data...
diff --git a/app/views/projects/tree/_submodule_item.html.haml b/app/views/projects/tree/_submodule_item.html.haml
deleted file mode 100644
index e563c8c4036..00000000000
--- a/app/views/projects/tree/_submodule_item.html.haml
+++ /dev/null
@@ -1,6 +0,0 @@
-%tr.tree-item
-  %td.tree-item-file-name
-    %i.fa.fa-archive.fa-fw
-    = submodule_link(submodule_item, @ref)
-  %td
-  %td.d-none.d-sm-table-cell
diff --git a/app/views/projects/tree/_tree_item.html.haml b/app/views/projects/tree/_tree_item.html.haml
deleted file mode 100644
index ce0cd95b468..00000000000
--- a/app/views/projects/tree/_tree_item.html.haml
+++ /dev/null
@@ -1,9 +0,0 @@
-%tr{ class: "tree-item #{tree_hex_class(tree_item)}" }
-  %td.tree-item-file-name
-    = tree_icon(type, tree_item.mode, tree_item.name)
-    - path = flatten_tree(@path, tree_item)
-    = link_to project_tree_path(@project, tree_join(@id || @commit.id, path)), class: 'str-truncated', title: path do
-      %span= path
-  %td.d-none.d-sm-table-cell.tree-commit
-  %td.tree-time-ago.text-right
-    = render 'projects/tree/spinner'
diff --git a/app/views/projects/tree/_tree_row.html.haml b/app/views/projects/tree/_tree_row.html.haml
index 0a5c6f048f7..8a27ea66523 100644
--- a/app/views/projects/tree/_tree_row.html.haml
+++ b/app/views/projects/tree/_tree_row.html.haml
@@ -1,6 +1,27 @@
-- if tree_row.type == :tree
-  = render partial: 'projects/tree/tree_item', object: tree_row, as: 'tree_item', locals: { type: 'folder' }
-- elsif tree_row.type == :blob
-  = render partial: 'projects/tree/blob_item', object: tree_row, as: 'blob_item', locals: { type: 'file' }
-- elsif tree_row.type == :commit
-  = render partial: 'projects/tree/submodule_item', object: tree_row, as: 'submodule_item'
+- tree_row_name = tree_row.name
+- tree_row_type = tree_row.type
+
+%tr{ class: "tree-item file_#{hexdigest(tree_row_name)}" }
+  %td.tree-item-file-name
+    - if tree_row_type == :tree
+      = tree_icon('folder', tree_row.mode, tree_row.name)
+      - path = flatten_tree(@path, tree_row)
+      %a.str-truncated{ href: fast_project_tree_path(@project, tree_join(@id || @commit.id, path)), title: path }
+        %span= path
+
+    - elsif tree_row_type == :blob
+      = tree_icon('file', tree_row.mode, tree_row_name)
+      %a.str-truncated{ href: fast_project_blob_path(@project, tree_join(@id || @commit.id, tree_row_name)), title: tree_row_name }
+        %span= tree_row_name
+      - if @lfs_blob_ids.include?(tree_row.id)
+        %span.badge.label-lfs.prepend-left-5 LFS
+
+    - elsif tree_row_type == :commit
+      = tree_icon('archive', tree_row.mode, tree_row.name)
+      = submodule_link(tree_row, @ref)
+
+  %td.d-none.d-sm-table-cell.tree-commit
+  %td.tree-time-ago.text-right
+    %span.log_loading.hide
+      %i.fa.fa-spinner.fa-spin
+      Loading commit data...
diff --git a/changelogs/unreleased/fast_project_blob_path.yml b/changelogs/unreleased/fast_project_blob_path.yml
new file mode 100644
index 00000000000..b56c9d9cf59
--- /dev/null
+++ b/changelogs/unreleased/fast_project_blob_path.yml
@@ -0,0 +1,5 @@
+---
+title: Improve performance of tree rendering in repositories with lots of items
+merge_request:
+author:
+type: performance
diff --git a/spec/helpers/tree_helper_spec.rb b/spec/helpers/tree_helper_spec.rb
index ffdf6561a53..ab4566e261b 100644
--- a/spec/helpers/tree_helper_spec.rb
+++ b/spec/helpers/tree_helper_spec.rb
@@ -3,7 +3,7 @@ require 'spec_helper'
 describe TreeHelper do
   let(:project) { create(:project, :repository) }
   let(:repository) { project.repository }
-  let(:sha) { 'ce369011c189f62c815f5971d096b26759bab0d1' }
+  let(:sha) { 'c1c67abbaf91f624347bb3ae96eabe3a1b742478' }
 
   describe '.render_tree' do
     before do
@@ -32,6 +32,49 @@ describe TreeHelper do
     end
   end
 
+  describe '.fast_project_blob_path' do
+    it 'generates the same path as project_blob_path' do
+      blob_path = repository.tree(sha, 'with space').entries.first.path
+      fast_path = fast_project_blob_path(project, blob_path)
+      std_path  = project_blob_path(project, blob_path)
+
+      expect(fast_path).to eq(std_path)
+    end
+
+    it 'generates the same path with encoded file names' do
+      tree = repository.tree(sha, 'encoding')
+      blob_path = tree.entries.find { |entry| entry.path == 'encoding/テスト.txt' }.path
+      fast_path = fast_project_blob_path(project, blob_path)
+      std_path  = project_blob_path(project, blob_path)
+
+      expect(fast_path).to eq(std_path)
+    end
+
+    it 'respects a configured relative URL' do
+      allow(Gitlab.config.gitlab).to receive(:relative_url_root).and_return('/gitlab/root')
+      blob_path = repository.tree(sha, '').entries.first.path
+      fast_path = fast_project_blob_path(project, blob_path)
+
+      expect(fast_path).to start_with('/gitlab/root')
+    end
+  end
+
+  describe '.fast_project_tree_path' do
+    let(:tree_path) { repository.tree(sha, 'with space').path }
+    let(:fast_path) { fast_project_tree_path(project, tree_path) }
+    let(:std_path) { project_tree_path(project, tree_path) }
+
+    it 'generates the same path as project_tree_path' do
+      expect(fast_path).to eq(std_path)
+    end
+
+    it 'respects a configured relative URL' do
+      allow(Gitlab.config.gitlab).to receive(:relative_url_root).and_return('/gitlab/root')
+
+      expect(fast_path).to start_with('/gitlab/root')
+    end
+  end
+
   describe 'flatten_tree' do
     let(:tree) { repository.tree(sha, 'files') }
     let(:root_path) { 'files' }
diff --git a/spec/views/projects/tree/_blob_item.html.haml_spec.rb b/spec/views/projects/tree/_tree_row.html.haml_spec.rb
index 6a477c712ff..3353b7665e2 100644
--- a/spec/views/projects/tree/_blob_item.html.haml_spec.rb
+++ b/spec/views/projects/tree/_tree_row.html.haml_spec.rb
@@ -1,6 +1,6 @@
 require 'spec_helper'
 
-describe 'projects/tree/_blob_item' do
+describe 'projects/tree/_tree_row' do
   let(:project) { create(:project, :repository) }
   let(:repository) { project.repository }
   let(:blob_item) { Gitlab::Git::Tree.where(repository, SeedRepo::Commit::ID, 'files/ruby').first }
@@ -31,10 +31,7 @@ describe 'projects/tree/_blob_item' do
     end
   end
 
-  def render_partial(blob_item)
-    render partial: 'projects/tree/blob_item', locals: {
-      blob_item: blob_item,
-      type: 'blob'
-    }
+  def render_partial(items)
+    render partial: 'projects/tree/tree_row', collection: [items].flatten
   end
 end