Date: Sat, 7 Sep 2024 23:59:41 +0200
From: Karsten Hilbert <Karsten.Hilbert@gmx.net>
To: Adrian Klaver <adrian.klaver@aklaver.com>
Cc: psycopg@lists.postgresql.org
Subject: Re: psycopg2: proper positioning of .commit() within try: except:
 blocks
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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 =3D psycopg2.connection()
	curs =3D conn.cursor()
	curs.execute(SQL)
	curs.close()
	conn.commit()
	conn.close()

Written more safely:

	conn =3D psycopg2.connection()
	curs =3D 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 =3D psycopg2.connection()
	curs =3D 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 ?

Karsten
=2D-
GPG  40BE 5B0E C98E 1713 AFA6  5BC0 3BEA AC80 7D4F C89B