Allow a 2 bytes margin:

- mysql will add a 2 bytes margin to the statement, so given a `max_allowed_packet` set to 1024 bytes, a 1024 bytes fixtures will no be inserted (mysql will throw an error)
- Preventing this by decreasing the max_allowed_packet by 2 bytes when doing the comparison with the actual statement size

1 files changed, 2 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 5e6ab1c16d..072a5337a5 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -568,7 +568,8 @@ module ActiveRecord
         end
 
         def max_allowed_packet
-          @max_allowed_packet ||= show_variable("max_allowed_packet")
+          bytes_margin = 2
+          @max_allowed_packet ||= (show_variable("max_allowed_packet") - bytes_margin)
         end
 
         def with_multi_statements