Fixup get transaction

[tdamsma]

I just realized I made a mistake in #62, checking for get_transaction on the transation instead of the session. Luckily SQLALchemy 1.4 is still backwards compatible, so that is why it didn't fail in the tests and shouldn't have any consequences for the moment.

And upon closer inspection, session.transaction (that is deprecated in 1.4+) returns the current (possibly nested) transaction and starts a new one if there is none. SQLALchemy 1.4+ makes a distinction between getting

• the current root transaction (if there is one) with session.get_transaction()
• the nested transaction: session.get_nested_transaction()
• starting a new transaction: session.begin

I added explicit checks for SQLALchemy >= 1.4.0 instead of hasattr/getattr, and made the distinction between nested and root transaction more explicit.

Not sure why I need to call root_transaction = session.get_transaction() or session.begin() and not just root_transaction = session.begin() as it seems to me that that should be equivalent; It seems to me that begin() should return the current root transaction if there is one but apparently this is not the case.

[icemac]

Generally it looks good to me.

Additionally a change log entry referencing the PR would be helpful.

[tdamsma]

Additionally a change log entry referencing the PR would be helpful.

Would this be version 1.5.0 or 1.4.1, as it is a fix of 1.4.0?

[icemac]

Would this be version 1.5.0 or 1.4.1, as it is a fix of 1.4.0?

I think 1.4.1 would be fine as it is a bugfix.

[icemac]

Is there still something which prevents us from merging this PR?

[icemac]

Thank you for this PR, it was included in #68 and is not in the 1.5 release of this package. Hopefully the change log entry I wrote meets the intention of this PR.

[tdamsma]

@icemac, @silenius sorry for not following up on this earlier, should have wrapped it up myself but it fell off my radar. Thanks!