Use SQL to find the gap instead of iterating

Also removes unnecessary methods causing extra queries

1 files changed, 24 insertions, 0 deletions

diff --git a/db/migrate/20190802012622_reorder_issues_project_id_relative_position_index.rb b/db/migrate/20190802012622_reorder_issues_project_id_relative_position_index.rb
new file mode 100644
index 00000000000..12088dd763f
--- /dev/null
+++ b/db/migrate/20190802012622_reorder_issues_project_id_relative_position_index.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+class ReorderIssuesProjectIdRelativePositionIndex < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  OLD_INDEX_NAME = 'index_issues_on_project_id_and_state_and_rel_position_and_id'
+  NEW_INDEX_NAME = 'index_issues_on_project_id_and_rel_position_and_state_and_id'
+
+  def up
+    add_concurrent_index :issues, [:project_id, :relative_position, :state, :id], order: { id: :desc }, name: NEW_INDEX_NAME
+
+    remove_concurrent_index_by_name :issues, OLD_INDEX_NAME
+  end
+
+  def down
+    add_concurrent_index :issues, [:project_id, :state, :relative_position, :id], order: { id: :desc }, name: OLD_INDEX_NAME
+
+    remove_concurrent_index_by_name :issues, NEW_INDEX_NAME
+  end
+end