Merge branch 'support-project-security-dashboard' into 'master'

Backport support project security dashboard changes

See merge request gitlab-org/gitlab-ce!22824

app/models/ci/pipeline.rb

@@ -181,22 +181,31 @@ module Ci
     #
     # ref - The name (or names) of the branch(es)/tag(s) to limit the list of
     #       pipelines to.
-    def self.newest_first(ref = nil)
+    # limit - This limits a backlog search, default to 100.
+    def self.newest_first(ref: nil, limit: 100)
       relation = order(id: :desc)
+      relation = relation.where(ref: ref) if ref
 
-      ref ? relation.where(ref: ref) : relation
+      if limit
+        ids = relation.limit(limit).select(:id)
+        # MySQL does not support limit in subquery
+        ids = ids.pluck(:id) if Gitlab::Database.mysql?
+        relation = relation.where(id: ids)
+      end
+
+      relation
     end
 
     def self.latest_status(ref = nil)
-      newest_first(ref).pluck(:status).first
+      newest_first(ref: ref).pluck(:status).first
     end
 
     def self.latest_successful_for(ref)
-      newest_first(ref).success.take
+      newest_first(ref: ref).success.take
     end
 
     def self.latest_successful_for_refs(refs)
-      relation = newest_first(refs).success
+      relation = newest_first(ref: refs).success
 
       relation.each_with_object({}) do |pipeline, hash|
         hash[pipeline.ref] ||= pipeline

spec/models/ci/pipeline_spec.rb

@@ -1043,6 +1043,11 @@ describe Ci::Pipeline, :mailer do
       expect(described_class.newest_first.pluck(:status))
         .to eq(%w[skipped failed success canceled])
     end
+
+    it 'searches limited backlog' do
+      expect(described_class.newest_first(limit: 1).pluck(:status))
+        .to eq(%w[skipped])
+    end
   end
 
   describe '.latest_status' do