Message-ID: <e8dc0835-b2f2-8cc1-fdd1-5994ab1b8582@aklaver.com>
Date: Thu, 14 Oct 2021 15:38:21 -0700
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.2.0
Subject: Re: psycopg3 transactions
Content-Language: en-US
To: Daniel Fortunov <postgresql@danielfortunov.com>,
 Daniele Varrazzo <daniele.varrazzo@gmail.com>,
 Paolo De Stefani <paolo@paolodestefani.it>, Psycopg <psycopg@postgresql.org>
References: <eb5cc5d20c520e32b5963a4044b70af1@paolodestefani.it>
 <CA+mi_8bXjHTrzDLQ+n_6K2MHVsr0J32X1HA28Ey9O+-Zm6JaeQ@mail.gmail.com>
 <9a99d2d110b121542d1ea0a05066858b@paolodestefani.it>
 <CA+mi_8afF2jMifiLSvL99+Ztupy1me7xDNAv0g47WxHWbwN9vw@mail.gmail.com>
 <CAH1rg6ZoQm=STwMR6AQ_FggxRxUn7qH_tLkRTfJTVYYdbTeL6w@mail.gmail.com>
 <trinity-cf9ddf31-623c-4512-beff-cf6d6d0116b8-1634205902640@3c-app-gmx-bs43>
 <CAH1rg6av5MR+yhEpwaxZNH+QrW+9ya9BQTx+w_Q9crm3e65yZQ@mail.gmail.com>
 <YWisObvZJNvpihtM@hermes.hilbert.loc>
From: Adrian Klaver <adrian.klaver@aklaver.com>
In-Reply-To: <YWisObvZJNvpihtM@hermes.hilbert.loc>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Archived-At: 
 <https://www.postgresql.org/message-id/e8dc0835-b2f2-8cc1-fdd1-5994ab1b8582%40aklaver.com>
Precedence: bulk

On 10/14/21 15:16, Karsten Hilbert wrote:
>> We are still "using transactions", just with more precise, more explicit*,
>> and more flexible* semantics, represented by a context manager.
>>
>> Rolling back a transaction is possible by raising a Rollback exception
>> within a block.
>>
>> I hope this answers your question but if not please describe the scenario
>> you are thinking about.
> 
> Personally, I think the autocommit=False approach is somewhat
> safer (more conservative) for the data:
> 
> 	One *always* is inside a transaction, and the default
> 	behaviour is to rollback.
> 
> 	Nothing is by accident automatically committed -- which can
> 	happen with autocommit=True.

+1

> 
> I would certainly suggest that a context manager calls
> .rollback() during teardown rather than .commit() -- the
> context manager cannot know whether actions really are to
> be committed, even if technically possible.

If I'm following that option exists:

https://www.psycopg.org/psycopg3/docs/api/connections.html#psycopg.Connection.transaction

force_rollback (bool) – Roll back the transaction at the end of the 
block even if there were no error (e.g. to try a no-op process).

> 
> Karsten
> --
> GPG  40BE 5B0E C98E 1713 AFA6  5BC0 3BEA AC80 7D4F C89B
> 
> 


-- 
Adrian Klaver
adrian.klaver@aklaver.com