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Message-ID: <452c4e48-5ea8-46cf-9826-7afaddb323e1@aklaver.com>
Date: Thu, 4 Sep 2025 13:16:20 -0700
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Subject: Re: Q: limit the length of log file entries?
To: =?UTF-8?Q?Albrecht_Dre=C3=9F?= <albrecht.dress@posteo.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-general@lists.postgresql.org
References: <574OKSN4.CDETQIBQ.ZESIWSCX@VP6CMSVU.ANT6WK46.P2K35XKE>
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From: Adrian Klaver <adrian.klaver@aklaver.com>
In-Reply-To: <574OKSN4.CDETQIBQ.ZESIWSCX@VP6CMSVU.ANT6WK46.P2K35XKE>
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On 9/4/25 12:43, Albrecht Dreß wrote:
> Am 04.09.25 20:21 schrieb(en) Adrian Klaver:
>>> "Psycopg 3 sends the query and the parameters to the server separately,
>>> instead of merging them on the client side. Server-side binding works
>>> for normal SELECT and data manipulation statements (INSERT, UPDATE,
>>> DELETE), but it doesn’t work with many other statements. For instance,
>>> it doesn’t work with SET or with NOTIFY:"
>>
>> As example:
>>
>> import psycopg2
>> import psycopg
>>
>> conpsyc2 = psycopg2.connect("dbname=test user=postgres")
>> conpsyc3 = psycopg.connect("dbname=test user=postgres")
>>
>> cur2 = conpsyc2.cursor()
>> cur3 = conpsyc3.cursor()
>>
>> cur2.execute("select * from csv_test where id = %s", [1])
>> cur3.execute("select * from csv_test where id = %s", [1])
>>
>> yields:
>>
>> --cur2
>> 2025-09-04 11:17:30.246 PDT [29695] postgres@test LOG:  statement: BEGIN
>> 2025-09-04 11:17:30.246 PDT [29695] postgres@test LOG:  statement:
>> select * from csv_test where id = 1
>>
>> --cur3
>> 2025-09-04 11:18:07.158 PDT [29703] postgres@test LOG:  statement: BEGIN
>> 2025-09-04 11:18:07.159 PDT [29703] postgres@test LOG:  execute
>> <unnamed>: select * from csv_test where id = $1
>> 2025-09-04 11:18:07.159 PDT [29703] postgres@test DETAIL:  Parameters:
>> $1 = '1'
> 
> Very nice example!  Looks as if the (anyway broken) script should be migrated to the the newer Python module – which, looking into the docs, shouldn't be too complex…

Just be sure to read:

https://www.psycopg.org/psycopg3/docs/basic/from_pg2.html

Things that I had to deal with:

1) These:

https://www.psycopg.org/docs/extras.html#fast-execution-helpers

don't exist in psycopg(3).

Made up for, in my cases, because executemany() is faster in psycopg as 
it uses pipeline mode when libpq 14+ is available.

2) COPY is not file based, so it's usage has changed. The examples here:

https://www.psycopg.org/psycopg3/docs/basic/copy.html#copy

are clear and it was not that difficult to change over.

3) with connection has changed. It now closes the connection as well as 
the transaction.

FYI, you can use:

https://www.psycopg.org/psycopg3/docs/advanced/cursors.html#client-side-binding-cursors

to keep the old client side binding style of parameters to help migrate 
code over in stages.

> 
> Thanks a lot for all your helpful insight,
> Albrecht.


-- 
Adrian Klaver
adrian.klaver@aklaver.com