Create finder for searching branch names via redis

app/finders/repositories/branch_names_finder.rb

+# frozen_string_literal: true
+
+module Repositories
+  class BranchNamesFinder
+    attr_reader :repository, :params
+
+    def initialize(repository, params = {})
+      @repository = repository
+      @params = params
+    end
+
+    def execute
+      return unless search
+
+      repository.search_branch_names(search)
+    end
+
+    private
+
+    def search
+      @params[:search].presence
+    end
+  end
+end

app/models/repository.rb

@@ -288,6 +288,10 @@ class Repository
     false
   end
 
+  def search_branch_names(pattern)
+    redis_set_cache.search('branch_names', pattern) { branch_names }
+  end
+
   def languages
     return [] if empty?
 

changelogs/unreleased/mc-backstage-use-redis-in-branch-finder.yml

+---
+title: Create finder for searching branch names via redis.
+merge_request: 58439
+author:
+type: performance

lib/gitlab/repository_set_cache.rb

@@ -49,5 +49,20 @@ module Gitlab
 
       write(key, yield)
     end
+
+    # Searches the cache set using SSCAN with the MATCH option. The MATCH
+    # parameter is the pattern argument.
+    # See https://redis.io/commands/scan#the-match-option for more information.
+    # Returns an Enumerator that enumerates all SSCAN hits.
+    def search(key, pattern, &block)
+      full_key = cache_key(key)
+
+      with do |redis|
+        exists = redis.exists(full_key)
+        write(key, yield) unless exists
+
+        redis.sscan_each(full_key, match: pattern)
+      end
+    end
   end
 end

spec/finders/repositories/branch_names_finder_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Repositories::BranchNamesFinder do
+  let(:project) { create(:project, :repository) }
+
+  let(:branch_names_finder) { described_class.new(project.repository, search: 'conflict-*') }
+
+  describe '#execute' do
+    subject(:execute) { branch_names_finder.execute }
+
+    it 'filters branch names' do
+      expect(execute).to contain_exactly(
+        'conflict-binary-file',
+        'conflict-resolvable',
+        'conflict-contains-conflict-markers',
+        'conflict-missing-side',
+        'conflict-start',
+        'conflict-non-utf8',
+        'conflict-too-large'
+      )
+    end
+  end
+end

spec/lib/gitlab/repository_set_cache_spec.rb

@@ -124,6 +124,18 @@ RSpec.describe Gitlab::RepositorySetCache, :clean_gitlab_redis_cache do
     end
   end
 
+  describe '#search' do
+    subject do
+      cache.search(:foo, 'val*') do
+        %w[value helloworld notvalmatch]
+      end
+    end
+
+    it 'returns search pattern matches from the key' do
+      is_expected.to contain_exactly('value')
+    end
+  end
+
   describe '#include?' do
     it 'checks inclusion in the Redis set' do
       cache.write(:foo, ['value'])

spec/models/repository_spec.rb

@@ -170,6 +170,22 @@ RSpec.describe Repository do
     end
   end
 
+  describe '#search_branch_names' do
+    subject(:search_branch_names) { repository.search_branch_names('conflict-*') }
+
+    it 'returns matching branch names' do
+      expect(search_branch_names).to contain_exactly(
+        'conflict-binary-file',
+        'conflict-resolvable',
+        'conflict-contains-conflict-markers',
+        'conflict-missing-side',
+        'conflict-start',
+        'conflict-non-utf8',
+        'conflict-too-large'
+      )
+    end
+  end
+
   describe '#list_last_commits_for_tree' do
     let(:path_to_commit) do
       {