Blacklist the use of "destroy_all"

This method usually has really bad performance implications, as it loads
rows into memory and deletes them one by one.

2 files changed, 23 insertions, 0 deletions

diff --git a/rubocop/cop/destroy_all.rb b/rubocop/cop/destroy_all.rb
new file mode 100644
index 00000000000..38b6cb40f91
--- /dev/null
+++ b/rubocop/cop/destroy_all.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    # Cop that blacklists the use of `destroy_all`.
+    class DestroyAll < RuboCop::Cop::Cop
+      MSG = 'Use `delete_all` instead of `destroy_all`. ' \
+        '`destroy_all` will load the rows into memory, then execute a ' \
+        '`DELETE` for every individual row.'
+
+      def_node_matcher :destroy_all?, <<~PATTERN
+        (send {send ivar lvar const} :destroy_all ...)
+      PATTERN
+
+      def on_send(node)
+        return unless destroy_all?(node)
+
+        add_offense(node, location: :expression)
+      end
+    end
+  end
+end
diff --git a/rubocop/rubocop.rb b/rubocop/rubocop.rb
index a427208cdab..88c9bbf24f4 100644
--- a/rubocop/rubocop.rb
+++ b/rubocop/rubocop.rb
@@ -27,3 +27,4 @@ require_relative 'cop/project_path_helper'
 require_relative 'cop/rspec/env_assignment'
 require_relative 'cop/rspec/factories_in_migration_specs'
 require_relative 'cop/sidekiq_options_queue'
+require_relative 'cop/destroy_all'