Wrong default type of READ COMMITTED transaction

[ant-zuev]

When specifying the READ COMMITTED isolation type, the RECORD_VERSION modifier is used:

python3-driver/src/firebird/driver/core.py

Lines 365 to 367 in b40e0d9

	isolation = (Isolation.READ_COMMITTED_RECORD_VERSION
	if self.isolation == Isolation.READ_COMMITTED
	else self.isolation)

although NO_RECORD_VERSION should be used by default.
In general we should not specify a modifier if user has only specified READ COMMITTED isolation, as the server will use NO_RECORD_VERSION for READ COMMITTED by default.

[pcisar]

Once again, I don't understand your problem. There is no such a thing a "vanilla" READ_COMMITTED isolation if Firebird. It's either RC + RECORD VERSION or RC + NO record version. Having Isolation.READ_COMMITTED defined in firebird-driver is and artifact for developers porting from old FDB driver that used predefined TPB buffers and where ISOLATION_LEVEL_READ_COMMITED was defined - as read committed RECORD VERSION, see:

https://github.com/FirebirdSQL/fdb/blob/master/fdb/fbcore.py#L367-L371

firebird-driver uses enum Isolation and different method to specify transaction parameters, so Isolation.READ_COMMITTED = -1 value was defined (note the value -1), so porting developers can use the familiar name to achieve the same result as with FDB.

New firebird-driver users should rather use the other Isolation values to be more clear about the transaction isolation level.