On 06/05/2017 05:52 PM, Uri Okrent wrote:
On Monday, May 29, 2017 at 12:27:51 PM UTC-4, Mike Bayer wrote:
I'm assuming this "invalidates the transaction" is on the Postgresql
side, e.g. you get "current transaction is aborted". There is a
simple
solution for that which is to use a savepoint, which with the ORM is
via
session.begin_nested().
http://docs.sqlalchemy.org/en/latest/orm/session_transaction.html#session-begin-nested
<http://docs.sqlalchemy.org/en/latest/orm/session_transaction.html#session-begin-nested>
Ah, right, SAVEPOINT. Thanks, that's perfect. Just a follow up
regarding the behavior. The docs provide the following example:
|
Session=sessionmaker()
session =Session()
session.add(u1)
session.add(u2)
session.begin_nested()# establish a savepoint
session.add(u3)
session.rollback()# rolls back u3, keeps u1 and u2
session.commit()# commits u1 and u2
|
It also says each use of begin_nested() must have a corresponding
commit() or rollback(). I got that the rollback in the example only
rolls back to the last savepoint (begin_nested()), but what would a
commit right after session.add(u3) do? It looks like the non-error case
would look like this:
the commit corresponding to begin_nested will emit RELEASE SAVEPOINT.
|
Session=sessionmaker()
session =Session()
session.add(u1)
session.add(u2)
session.begin_nested()# establish a savepoint
session.add(u3)
session.commit()# ???
session.commit()# ???
|
what does each commit actually do?
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