diff options
Diffstat (limited to 'lib/sqlalchemy/pool.py')
| -rw-r--r-- | lib/sqlalchemy/pool.py | 25 |
1 files changed, 11 insertions, 14 deletions
diff --git a/lib/sqlalchemy/pool.py b/lib/sqlalchemy/pool.py index 7cd2c3d0d..f1f278e91 100644 --- a/lib/sqlalchemy/pool.py +++ b/lib/sqlalchemy/pool.py @@ -178,25 +178,22 @@ class Pool(log.Identified): any data changes present on the transaction are committed unconditionally. * ``None`` - don't do anything on the connection. - This setting should only be made on a database + This setting should generally only be made on a database that has no transaction support at all, - namely MySQL MyISAM. By not doing anything, - performance can be improved. This - setting should **never be selected** for a - database that supports transactions, - as it will lead to deadlocks and stale - state. - * ``"none"`` - same as ``None`` - - .. versionadded:: 0.9.10 + namely MySQL MyISAM; when used on this backend, performance + can be improved as the "rollback" call is still expensive on + MySQL. It is **strongly recommended** that this setting not be + used for transaction-supporting databases in conjunction with + a persistent pool such as :class:`.QueuePool`, as it opens + the possibility for connections still in a transaction to be + idle in the pool. The setting may be appropriate in the + case of :class:`.NullPool` or special circumstances where + the connection pool in use is not being used to maintain connection + lifecycle. * ``False`` - same as None, this is here for backwards compatibility. - .. versionchanged:: 0.7.6 - :paramref:`.Pool.reset_on_return` accepts ``"rollback"`` - and ``"commit"`` arguments. - :param events: a list of 2-tuples, each of the form ``(callable, target)`` which will be passed to :func:`.event.listen` upon construction. Provided here so that event listeners |