Re: Changing set_session implementation

On Sat, Feb 04, 2017 at 04:33:13PM +0000, Daniele Varrazzo wrote:

> I've changed the set_session/set_isolation_level/autocommit connection
> methods and properties to use better the BEGIN parameters
...
> Conversely:
>
> conn.set_session(readonly=True, autocommit=True)

Does this mean that

conn.set_isolation_level(ISOLATION_LEVEL_AUTOCOMMIT)

is now a no-op as observed by the following log snippet or
just diverted to set_session(autocommit=True) ?

code:

_log.debug('conn state now: %s', gmPG2.capture_conn_state(self.conn))
_log.debug('setting isolation level to autocommit - should be redundant ?')
self.conn.set_isolation_level(0)
_log.debug('conn state now: %s', gmPG2.capture_conn_state(self.conn))

log:

2017-07-27 16:03:01 DEBUG gm.bootstrapper MainThread (-1219281664) (./bootstrap_gm_db_system.py::__create_db() #810): conn state now: <connection object at 0xb64eca04; dsn: 'dbname=gnumed_v21 port=5432 user=postgres sslmode=prefer fallback_application_name=GNUmed client_encoding=utf8 application_name=postgres(at)template(dot)db', closed: 0>
type: <class 'psycopg2.extras.DictConnection'>
identity: 3058616836
backend PID: 2864
protocol version: 3
encoding: UTF8
isolation level (psyco): 3 (ISOLATION_LEVEL_SERIALIZABLE)
readonly: False
autocommit: True
closed: 0
connection status: 1 (STATUS_READY)
transaction status: 0 (TRANSACTION_STATUS_IDLE)
deferrable: None
async: 0
executing async op: False
2017-07-27 16:03:01 DEBUG gm.bootstrapper MainThread (-1219281664) (./bootstrap_gm_db_system.py::__create_db() #811): setting isolation level to autocommit - should be redundant ?
2017-07-27 16:03:01 DEBUG gm.bootstrapper MainThread (-1219281664) (./bootstrap_gm_db_system.py::__create_db() #813): conn state now: <connection object at 0xb64eca04; dsn: 'dbname=gnumed_v21 port=5432 user=postgres sslmode=prefer fallback_application_name=GNUmed client_encoding=utf8 application_name=postgres(at)template(dot)db', closed: 0>
type: <class 'psycopg2.extras.DictConnection'>
identity: 3058616836
backend PID: 2864
protocol version: 3
encoding: UTF8
isolation level (psyco): 3 (ISOLATION_LEVEL_SERIALIZABLE)
readonly: False
autocommit: True
closed: 0
connection status: 1 (STATUS_READY)
transaction status: 0 (TRANSACTION_STATUS_IDLE)
deferrable: None
async: 0
executing async op: False

Note that it doesn't actually change the isolation level
(which makes sense because autocommit mode is not an
isolation level). Should conn.isolation_level show
ISOLATION_LEVEL_DEFAULT in this case (meaning "use what the
server/db is configured for") ? It doesn't seem to make a
roundtrip to the server to _get_ the default because the
database in question defaults to READ_COMMITED. The
SERIALIZABLE results from an earlier call to
.set_isolation_mode() in my code.

(Also note that the connection had already been set to
autocommit by "set_session(autocommit=True)" before.)

Thanks for the clarification,
Karsten
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