Merge pull request #37184 from dylanahsmith/read-query-comment-prefix

activerecord: Allow comment prefix in queries when preventing writes

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -77,6 +77,7 @@ class AbstractAdapter
       include Savepoints
 
       SIMPLE_INT = /\A\d+\z/
+      COMMENT_REGEX = %r{/\*(?:[^\*]|\*[^/])*\*/}m
 
       attr_accessor :pool
       attr_reader :visitor, :owner, :logger, :lock
@@ -103,8 +104,8 @@ def self.type_cast_config_to_boolean(config)
       end
 
       def self.build_read_query_regexp(*parts) # :nodoc:
-        parts = parts.map { |part| /\A[\(\s]*#{part}/i }
-        Regexp.union(*parts)
+        parts = parts.map { |part| /#{part}/i }
+        /\A(?:[\(\s]|#{COMMENT_REGEX})*#{Regexp.union(*parts)}/
       end
 
       def self.quoted_column_names # :nodoc:

activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb

@@ -237,7 +237,7 @@ def test_doesnt_error_when_a_read_query_with_leading_chars_is_called_while_preve
     @conn.execute("INSERT INTO `engines` (`car_id`) VALUES ('138853948594')")
 
     @connection_handler.while_preventing_writes do
-      assert_equal 1, @conn.execute("(\n( SELECT `engines`.* FROM `engines` WHERE `engines`.`car_id` = '138853948594' ) )").entries.count
+      assert_equal 1, @conn.execute("/*action:index*/(\n( SELECT `engines`.* FROM `engines` WHERE `engines`.`car_id` = '138853948594' ) )").entries.count
     end
   end