That makes complete sense now, thanks Mike:-) Soumaya
Le dim. 4 avr. 2021 à 18:53, Mike Bayer <mike...@zzzcomputing.com> a écrit : > If you are using the legacy engine, that is, without "future=True" in > create_engine(), SQLAlchemy autocommits statements that have strings like > "CREATE TABLE", "INSERT", etc. This is called "library level autocommit", > it's deprecated and the whole thing is documented at > https://docs.sqlalchemy.org/en/14/core/connections.html#library-level-e-g-emulated-autocommit > > > > On Sun, Apr 4, 2021, at 1:47 PM, Soumaya Mauthoor wrote: > > 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/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/5d474102-1212-4e8e-b26e-a78815ed5829n%40googlegroups.com > <https://groups.google.com/d/msgid/sqlalchemy/5d474102-1212-4e8e-b26e-a78815ed5829n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/4cbda2cc-09ef-4a5c-be20-3bc710898fe0%40www.fastmail.com > <https://groups.google.com/d/msgid/sqlalchemy/4cbda2cc-09ef-4a5c-be20-3bc710898fe0%40www.fastmail.com?utm_medium=email&utm_source=footer> > . > > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/CAN14jWQsMN66PBeh0Vg7xu4UPHecMqZut-bGccwdAvLLoZCHNQ%40mail.gmail.com > <https://groups.google.com/d/msgid/sqlalchemy/CAN14jWQsMN66PBeh0Vg7xu4UPHecMqZut-bGccwdAvLLoZCHNQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to a topic in the > Google Groups "sqlalchemy" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/sqlalchemy/sfAPI9_vwaE/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > sqlalchemy+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/2a6c2fcc-7bbe-44cf-a232-e9131cc7f436%40www.fastmail.com > <https://groups.google.com/d/msgid/sqlalchemy/2a6c2fcc-7bbe-44cf-a232-e9131cc7f436%40www.fastmail.com?utm_medium=email&utm_source=footer> > > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/CAN14jWSQyFAL_iOVV%3DvsyBhOB86di__HiP2odq9cxoZ%2BzzscoQ%40mail.gmail.com > <https://groups.google.com/d/msgid/sqlalchemy/CAN14jWSQyFAL_iOVV%3DvsyBhOB86di__HiP2odq9cxoZ%2BzzscoQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/db166aad-37ca-46a1-b728-c652a74b05e2%40www.fastmail.com > <https://groups.google.com/d/msgid/sqlalchemy/db166aad-37ca-46a1-b728-c652a74b05e2%40www.fastmail.com?utm_medium=email&utm_source=footer> > . > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sqlalchemy/CAN14jWSfVyP72BNb2rtLH97b8s7bQ5rjZNTHOd5bVEnH%2BbwbPw%40mail.gmail.com.
