Add specs for cached queries

- Add changelog

changelogs/unreleased/217580-improve-performance-of-blob.yml

+---
+title: Reduce 'cached' query calls for Banzai
+merge_request: 36735
+author:
+type: performance

spec/lib/banzai/filter/label_reference_filter_spec.rb

@@ -31,6 +31,19 @@ RSpec.describe Banzai::Filter::LabelReferenceFilter do
     expect(doc.css('a').first.attr('class')).to eq 'gfm gfm-label has-tooltip gl-link gl-label-link'
   end
 
+  it 'avoids N+1 cached queries', :use_sql_query_cache, :request_store do
+    # Run this once to establish a baseline
+    reference_filter("Label #{reference}")
+
+    control_count = ActiveRecord::QueryRecorder.new(skip_cached: false) do
+      reference_filter("Label #{reference}")
+    end
+
+    labels_markdown = Array.new(10, "Label #{reference}").join('\n')
+
+    expect { reference_filter(labels_markdown) }.not_to exceed_all_query_limit(control_count.count)
+  end
+
   it 'includes a data-project attribute' do
     doc = reference_filter("Label #{reference}")
     link = doc.css('a').first

spec/lib/banzai/reference_parser/snippet_parser_spec.rb

@@ -33,6 +33,17 @@ RSpec.describe Banzai::ReferenceParser::SnippetParser do
         project.project_feature.update_attribute(:snippets_access_level, ProjectFeature::ENABLED)
       end
 
+      it 'avoids N+1 cached queries', :use_sql_query_cache do
+        # Run this once to establish a baseline
+        visible_references(:public)
+
+        control_count = ActiveRecord::QueryRecorder.new(skip_cached: false) do
+          subject.nodes_visible_to_user(user, [link])
+        end
+
+        expect { subject.nodes_visible_to_user(user, Array.new(10, link)) }.not_to exceed_all_query_limit(control_count.count)
+      end
+
       it 'creates a reference for guest for a public snippet' do
         expect(visible_references(:public)).to eq([link])
       end