Merge branch 'sh-clean-duplicate-ci-trigger-request-indexes' into 'master'

Clean up duplicate indexes on ci_trigger_requests

Closes #34818

See merge request gitlab-org/gitlab!19053

changelogs/unreleased/sh-clean-duplicate-ci-trigger-request-indexes.yml

+---
+title: Clean up duplicate indexes on ci_trigger_requests
+merge_request: 19053
+author:
+type: fixed

db/migrate/20191016072826_replace_ci_trigger_requests_index.rb

@@ -10,7 +10,12 @@ class ReplaceCiTriggerRequestsIndex < ActiveRecord::Migration[5.2]
   def up
     add_concurrent_index :ci_trigger_requests, [:trigger_id, :id], order: { id: :desc }
 
-    remove_concurrent_index :ci_trigger_requests, [:trigger_id]
+    # Some installations have legacy, duplicate indexes on
+    # ci_trigger_requests.trigger_id. Rails won't drop them without an
+    # explicit name: https://gitlab.com/gitlab-org/gitlab/issues/34818
+    old_index_names.each do |name|
+      remove_concurrent_index :ci_trigger_requests, [:trigger_id], name: name
+    end
   end
 
   def down
@@ -18,4 +23,10 @@ class ReplaceCiTriggerRequestsIndex < ActiveRecord::Migration[5.2]
 
     remove_concurrent_index :ci_trigger_requests, [:trigger_id, :id], order: { id: :desc }
   end
+
+  private
+
+  def old_index_names
+    indexes(:ci_trigger_requests).select { |i| i.columns == ['trigger_id'] }.map(&:name)
+  end
 end