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Date: Sat, 7 Sep 2024 14:47:49 -0700
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Subject: Re: psycopg2: proper positioning of .commit() within try: except:
 blocks
To: Karsten Hilbert <Karsten.Hilbert@gmx.net>
Cc: psycopg@lists.postgresql.org
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From: Adrian Klaver <adrian.klaver@aklaver.com>
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On 9/7/24 14:20, Karsten Hilbert wrote:
> Am Sat, Sep 07, 2024 at 02:09:28PM -0700 schrieb Adrian Klaver:
> 
>>> Right, and this was suggested elsewhere ;)
>>>
>>> And, yeah, the actual code is much more involved :-D
>>>
>>
>> I see that.
>>
>> The question is does the full code you show fail?
>>
>> The code sample you show in your original post is doing something very different then
>> what you show in your latest post. At this point I do not understand the exact problem
>> we are dealing with.
> 
> We are not dealing with an unsolved problem. I had been
> asking for advice  where to best place that .commit() call in
> case I am overlooking benefits and drawbacks of choices.
> 
> The
> 
> 	try:
> 		do something
> 	except:
> 		log something
> 	finally:
> 		.commit()
> 
> cadence is fairly Pythonic and elegant in that it ensures the
> the .commit() will always be reached regardless of exceptions
> being thrown or not and them being handled or not.

Elegant is nice, but correct is better:)

> 
> It is also insufficient because the .commit() itself may
> elicit exceptions (from the database).

Yeah with Serializable that is part of the package:

"While PostgreSQL's Serializable transaction isolation level only allows 
concurrent transactions to commit if it can prove there is a serial 
order of execution that would produce the same effect ..."


> Boring and repetitive and safe(r):
> 
> 	try:
> 		do something
> 	except:
> 		log something
> 	try:
> 		.commit()
> 	except:
> 		log something
> 
> I eventually opted for the last version, except for factoring
> out the second try: except: block.

I'm not following, if you do that then you won't have a commit.

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

-- 
Adrian Klaver
adrian.klaver@aklaver.com