Don't swallow exceptions in transctional statements

The MySQL connection adapater swallows all StandardError exceptions,
which includes Mysql::Error and Mysql2::Error. The comment in the
exception clause claims errors thrown here indicate that transactions
aren't supported by the server but that isn't necessarily true. It's
possible the MySQL server has gone away and swallowing a failed commit
may let the application return a successful response when the data has
not been saved. Also, replication libraries like Galera require that the
application handle exceptions thrown at BEGIN/COMMIT.

I'm unable to determine what version of MySQL threw an exception for
transactional statements. I tried as far back as 3.23.49 with InnoDB
disabled but BEGIN & COMMIT statements do not throw an error. If there's
a real case for this logic to continue, we could instead push this
behavior into a configuration setting.

The exception swallowing has been there since the beginning:
db045dbbf60b53dbe013ef25554fd013baf88134

2 files changed, 0 insertions, 10 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 138ab811dc..9a88be5219 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -314,27 +314,19 @@ module ActiveRecord
 
       def begin_db_transaction
         execute "BEGIN"
-      rescue
-        # Transactions aren't supported
       end
 
       def begin_isolated_db_transaction(isolation)
         execute "SET TRANSACTION ISOLATION LEVEL #{transaction_isolation_levels.fetch(isolation)}"
         begin_db_transaction
-      rescue
-        # Transactions aren't supported
       end
 
       def commit_db_transaction #:nodoc:
         execute "COMMIT"
-      rescue
-        # Transactions aren't supported
       end
 
       def rollback_db_transaction #:nodoc:
         execute "ROLLBACK"
-      rescue
-        # Transactions aren't supported
       end
 
       # In the simple case, MySQL allows us to place JOINs directly into the UPDATE
diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index 88c9494fc6..d61847506d 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -468,8 +468,6 @@ module ActiveRecord
 
       def begin_db_transaction #:nodoc:
         exec_query "BEGIN"
-      rescue Mysql::Error
-        # Transactions aren't supported
       end
 
       private