Hey Mike
Sorry to be a pain but I finally got postgresql working on my laptop and
I'm getting the same behaviour as for sqlite (see below). I'm obviously
doing something wrong, any idea where? I'm writing an in-house tutorial on
sqlalchemy for colleagues, including an explanation of why we set the
Transaction Isolation Level to autocommit, so it would be great to have an
example :-)
>>> from sqlalchemy import text,create_engine
>>> c =
create_engine('postgresql://***:***@localhost:5432/postgres').connect()
>>> c.execute(text('create table test(col1 int)'))
<sqlalchemy.engine.cursor.LegacyCursorResult object at 0x7ffc412b91f0>
>>> del c
>>> c =
create_engine('postgresql://***:***@localhost:5432/postgres').connect()
>>> c.execute(text('select * from test')).fetchall()
[]
Thanks
Soumaya
Le jeu. 1 avr. 2021 à 18:33, Soumaya Mauthoor <soumaya.mauth...@gmail.com>
a écrit :
> Ooooh I see thanks for clarifying :-)
>
> Soumaya
>
> On Thu, 1 Apr 2021, 17:34 Mike Bayer, <mike...@zzzcomputing.com> wrote:
>
>>
>>
>> On Thu, Apr 1, 2021, at 11:20 AM, Soumaya Mauthoor wrote:
>>
>> Hello Mike
>>
>> Thanks for quick response! I don't have postgres installed right now so I
>> tried with sqlite, which is also autocommit by default. Example
>>
>>
>> ahha - that's again a very specific quirk of the pysqlite driver that it
>> does not autobegin the transaction if DDL is encountered, which is a bug in
>> the driver, see https://bugs.python.org/issue9924
>>
>> This autocommit situation has been mostly unchanged since I first started
>> SQLAlchemy in 2005. So I've been working with this behavior literally
>> every day for sixteen years with a dozen or more DBAPI drivers. It's
>> safe to trust I know what i am speaking of ! :)
>>
>>
>>
>>
>>
>>
>>
>> :
>>
>> >>> from sqlalchemy import text, create_engine
>> >>> e = create_engine('sqlite:///foo.db')
>> >>> with e.connect() as conn: conn.execute(text('create table test(int
>> col1)'))
>> ...
>> <sqlalchemy.engine.cursor.LegacyCursorResult object at 0x7f6257fba7c0>
>> >>> e.execute('select * from test').fetchall()
>> []
>>
>> I didn't commit the transaction, but it seems to have autocommited since
>> I can query it in the following query?
>>
>> Soumaya
>>
>> Le jeu. 1 avr. 2021 à 15:27, Mike Bayer <mike...@zzzcomputing.com> a
>> écrit :
>>
>>
>>
>>
>> On Thu, Apr 1, 2021, at 10:06 AM, sumau wrote:
>>
>> Hello
>>
>> Following advice from this article:
>> https://www.oddbird.net/2014/06/14/sqlalchemy-postgres-autocommit/
>>
>> and because we run large, consecutive queries, we set our transaction
>> isolation level to 'autocommit' when connecting to our postgres DB. This
>> means we cannot create explicit transactions and use begin() and commit():
>> https://www.oddbird.net/2014/06/14/sqlalchemy-postgres-autocommit/
>>
>> This has not a problem so far because we can create another (temporary)
>> connection when we do want to have a roll-backable transaction. However
>> since postgres DB is set to autocommit by default, I was wondering whether
>> setting the transaction isolation level to 'autocommit' was needlessly
>> complicated?
>>
>>
>> the Python DBAPI is transactional by default and the "autocommit" feature
>> of many DBAPIs is not part of the specification:
>> https://www.python.org/dev/peps/pep-0249/ . the psycopg2 driver, as
>> well as all other DBAPI drivers, are not in autocommit by default.
>>
>>
>>
>>
>>
>>
>> For example in the example explained here: the
>> https://docs.sqlalchemy.org/en/14/tutorial/dbapi_transactions.html#getting-a-connection
>> the query will still be committed, even if don't explicitly commit the
>> transaction or the transaction isolation level to 'autocommit'.
>>
>>
>> respectfully, that is incorrect for the DBAPI drivers included in
>> SQLAlchemy, provided you aren't using MySQL with MyISAM tables. try it out
>>
>>
>>
>>
>>
>> Regards
>> Soumaya
>>
>>
>> --
>> SQLAlchemy -
>> The Python SQL Toolkit and Object Relational Mapper
>>
>> http://www.sqlalchemy.org/
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>>
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>>
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>>
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>
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SQLAlchemy -
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http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
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