Feedback-ID: i76984098:Fastmail
Message-ID: <75723bad-7914-4728-a567-a061e4d3c7d6@aklaver.com>
Date: Sat, 7 Sep 2024 15:09:28 -0700
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: psycopg2: proper positioning of .commit() within try: except:
 blocks
To: Karsten Hilbert <Karsten.Hilbert@gmx.net>
Cc: psycopg@lists.postgresql.org
References: <Ztx1sZMGTnA3eLP1@hermes.hilbert.loc>
 <7cb50df2-9c76-477f-91c9-e149c7637104@aklaver.com>
 <ZtytJMhyvtExPxfF@hermes.hilbert.loc>
 <5ee80b84-f04b-454d-ab39-45572e0751a1@aklaver.com>
 <Zty7ZCMwKQl4C4Id@hermes.hilbert.loc>
 <4a1b12fc-24b7-4c7e-b1f2-6ec9c5f341c2@aklaver.com>
 <ZtzDubguRDWXwV-t@hermes.hilbert.loc>
 <a663dfcf-3ca4-41d0-9022-1ad01d6b6d5f@aklaver.com>
 <ZtzMzYTlqN4l5ivN@hermes.hilbert.loc>
Content-Language: en-US
From: Adrian Klaver <adrian.klaver@aklaver.com>
In-Reply-To: <ZtzMzYTlqN4l5ivN@hermes.hilbert.loc>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Archived-At: 
 <https://www.postgresql.org/message-id/75723bad-7914-4728-a567-a061e4d3c7d6%40aklaver.com>
Precedence: bulk

On 9/7/24 14:59, Karsten Hilbert wrote:
> Am Sat, Sep 07, 2024 at 02:47:49PM -0700 schrieb Adrian Klaver:
> 
>>> It is also insufficient because the .commit() itself may
>>> elicit exceptions (from the database).
>>
>> Yeah with Serializable that is part of the package:
> 
> No complaints :-)
> 
> 
>>> 	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.
> 
> Perhaps my pseudo-code was to abbreviated.
> 
> 	conn = psycopg2.connection()
> 	curs = conn.cursor()
> 	curs.execute(SQL)
> 	curs.close()
> 	conn.commit()
> 	conn.close()
> 
> Written more safely:
> 
> 	conn = psycopg2.connection()
> 	curs = conn.cursor()
> 	try:
> 		curs.execute(SQL)
> 	except SOME_PG_EXCEPTION_VIA_PSYCOPG2:
> 		some_panicstricken_logging()
> 	curs.close()
> 	try:
> 		conn.commit()
> 	except SOME_PG_EXCEPTION_VIA_PSYCOPG2__SUCH_AS_SERIALIZATION_ERROR:
> 		some_more_of_the_panicstricken_logging()
> 	conn.close()
> 
> now factored out:
> 
> 	def __commit_me_logging_errors(commit_func):
> 		try:
> 			commit_func()
> 		except SOME_PG_EXCEPTION_VIA_PSYCOPG2__SUCH_AS_SERIALIZATION_ERROR:
> 			some_more_of_the_panicstricken_logging()
> 		return
> 
> 	conn = psycopg2.connection()
> 	curs = conn.cursor()
> 	try:
> 		curs.execute(SQL)
> 	except SOME_PG_EXCEPTION_VIA_PSYCOPG2:
> 		some_panicstricken_logging()
> 	curs.close()
> 	__commit_me_logging_errors(conn.commit)
> 	conn.close()
> 
> More clear ?

Yes.


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

-- 
Adrian Klaver
adrian.klaver@aklaver.com