[Sqlalchemy-tickets] Issue #3108: Difference between flushing in outer transaction and committing in nested transaction (zzzeek/sqlalchemy)

[Torsten L. <iss...@bi...>]

New issue 3108: Difference between flushing in outer transaction and committing in nested transaction
https://bitbucket.org/zzzeek/sqlalchemy/issue/3108/difference-between-flushing-in-outer

Torsten Landschoff:

After introducing nested transactions into our software I was greeted with a flurry of ObjectDeletedErrors. It turned out that it makes a huge difference if a change is committed inside a nested transaction or flushed inside the main transaction.

>From the database side I expect these to be equivalent:

## Original instructions ##

```
#!sql

begin;
-- add stuff to the database
rollback;
```

## Updated instructions using nested transactions ##

```
#!sql

begin;
savepoint inner;
-- add stuff to the database
release savepoint inner;
rollback;
```

# Rationale #

When the instructions inside the nested transaction complete successfully, it should make no difference if they are inside a savepoint demarcation or not.

# Example code #

Please have a look at the attached file nested_rollback.rst. It runs to completion here without error but illustrates the current problem. You can run it using

```
#!sh

python -m doctest nested_rollback.rst
```

This seems to be related to issue #2658.