Reduce queries in IssueReferenceFilterbanzai-issue-filter-queries

This reduces the number of queries executed in IssueReferenceFilter by
retrieving the various projects/issues that may be referenced in batches
_before_ iterating over all the HTML nodes.

A chunk of the logic resides in AbstractReferenceFilter so it can be
re-used by other filters in the future.

2 files changed, 79 insertions, 3 deletions

diff --git a/lib/banzai/filter/abstract_reference_filter.rb b/lib/banzai/filter/abstract_reference_filter.rb
index db95d7c908b..4815bafe238 100644
--- a/lib/banzai/filter/abstract_reference_filter.rb
+++ b/lib/banzai/filter/abstract_reference_filter.rb
@@ -103,7 +103,7 @@ module Banzai
         ref_pattern = object_class.reference_pattern
         link_pattern = object_class.link_reference_pattern
 
-        each_node do |node|
+        nodes.each do |node|
           if text_node?(node) && ref_pattern
             replace_text_when_pattern_matches(node, ref_pattern) do |content|
               object_link_filter(content, ref_pattern)
@@ -206,6 +206,55 @@ module Banzai
         text
       end
 
+      # Returns a Hash containing all object references (e.g. issue IDs) per the
+      # project they belong to.
+      def references_per_project
+        @references_per_project ||= begin
+          refs = Hash.new { |hash, key| hash[key] = Set.new }
+
+          regex = Regexp.union(object_class.reference_pattern,
+                               object_class.link_reference_pattern)
+
+          nodes.each do |node|
+            node.to_html.scan(regex) do
+              project = $~[:project] || current_project_path
+
+              refs[project] << $~[object_sym]
+            end
+          end
+
+          refs
+        end
+      end
+
+      # Returns a Hash containing referenced projects grouped per their full
+      # path.
+      def projects_per_reference
+        @projects_per_reference ||= begin
+          hash = {}
+          refs = Set.new
+
+          references_per_project.each do |project_ref, _|
+            refs << project_ref
+          end
+
+          find_projects_for_paths(refs.to_a).each do |project|
+            hash[project.path_with_namespace] = project
+          end
+
+          hash
+        end
+      end
+
+      # Returns the projects for the given paths.
+      def find_projects_for_paths(paths)
+        Project.where_paths_in(paths).includes(:namespace)
+      end
+
+      def current_project_path
+        @current_project_path ||= project.path_with_namespace
+      end
+
       private
 
       def project_refs_cache
diff --git a/lib/banzai/filter/issue_reference_filter.rb b/lib/banzai/filter/issue_reference_filter.rb
index 2496e704002..2614261f9eb 100644
--- a/lib/banzai/filter/issue_reference_filter.rb
+++ b/lib/banzai/filter/issue_reference_filter.rb
@@ -11,13 +11,40 @@ module Banzai
         Issue
       end
 
-      def find_object(project, id)
-        project.get_issue(id)
+      def find_object(project, iid)
+        issues_per_project[project][iid]
       end
 
       def url_for_object(issue, project)
         IssuesHelper.url_for_issue(issue.iid, project, only_path: context[:only_path])
       end
+
+      def project_from_ref(ref)
+        projects_per_reference[ref || current_project_path]
+      end
+
+      # Returns a Hash containing the issues per Project instance.
+      def issues_per_project
+        @issues_per_project ||= begin
+          hash = Hash.new { |h, k| h[k] = {} }
+
+          projects_per_reference.each do |path, project|
+            issue_ids = references_per_project[path]
+
+            next unless project.default_issues_tracker?
+
+            project.issues.where(iid: issue_ids.to_a).each do |issue|
+              hash[project][issue.iid] = issue
+            end
+          end
+
+          hash
+        end
+      end
+
+      def find_projects_for_paths(paths)
+        super(paths).includes(:gitlab_issue_tracker_service)
+      end
     end
   end
 end