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Message-ID: <9f60eb26-7d34-4228-bd78-74c6deb90e54@aklaver.com>
Date: Thu, 19 Dec 2024 08:34:41 -0800
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Subject: Re: Intermittent errors when fetching cursor rows on PostgreSQL 16
To: Enrico Schenone <eschenone@cleistech.it>,
 pgsql-general@lists.postgresql.org
Cc: Massimo Catti <mcatti@cleistech.it>, Livio Pizzolo <lpizzolo@cleistech.it>
References: <446423eb-4a4e-4135-bbb8-4d0e5c7aac3b@cleistech.it>
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 <6ce80aaa-970b-4432-938a-39a07f811599@cleistech.it>
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From: Adrian Klaver <adrian.klaver@aklaver.com>
In-Reply-To: <6ce80aaa-970b-4432-938a-39a07f811599@cleistech.it>
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On 12/18/24 23:52, Enrico Schenone wrote:
> Good day, Adrian.
> First of all I thank-you for you answer.

> At the time the error occurs, dozens of other SQL sessions are active & 
> running on DB server, and no-one is reporting any error at-all (not only 
> fetch errors).
> This happens sometimes also in system with no (or low) stress situations.
> 
> One of things I don't understand is why at client side I get the XX001 
> error on the FETCH (normally the first fetch) while at server side I 
> heve no error related to the fetch forward ?

Where are you fetching the client error messages from?

> Another is why in the meantime no other client application report an 
> error, considering that there may be several parallel instances of the 
> same client application ?
> And finally why after seconds or minutes the same process newly 
> instantiated works with no more errors ?

Answers to this and the below is going to need the client code.

> 
> I can suppose that the client closes the connection once got the XX001 
> error, but I can't say why it receives this error while it is not 
> reported at server side and not block i/o error is reported.
> Is it a false positive or what ?
> 
> Four Js support said <We use the standard C API provided by the DB 
> vendor. In the case of PostgreSQL, we use the C API client - 
> https://www.postgresql.org/docs/current/libpq.html >
> 
> At client side I have installed the following PostgreSQL packages ...
> 
>      postgresql-client-16:amd64/jammy-pgdg 16.5-1.pgdg22.04+1 
> upgradeable to 16.6-1.pgdg22.04+1
>      postgresql-client-common:all/jammy-pgdg 262.pgdg22.04+1 upgradeable 
> to 267.pgdg22.04+1
> 
> Best regards.
> Enrico
> 
> 
> *Enrico Schenone*
> Software Architect
> 
> *Cleis Tech s.r.l.* - www.gruppocleis.it
> Sede di Genova, Via Paolo Emilio Bensa, 2 - 16124 Genova, ITALY
> Tel: +39-0104071400   Fax: +39-0104073276
> Mobile: +39-320 7709352
> E-mail: eschenone@cleistech.it
> 
> <https://gruppocleis.it><https://ibm.biz/BdqAJh>
> 
> <https://ibm.biz/BdqAJh>
> <https://ibm.biz/BdqAJh>
> Il 19/12/24 00:11, Adrian Klaver ha scritto:
>> On 12/17/24 08:30, Enrico Schenone wrote:
>>> Good day.
>>> My name is Enrico Schenone, from Genoa, Italy.
>>> I'm a software achitect working at Cleis Tech - Genoa - Italy  - 
>>> http://gruppocleis.it
>>> Me and my team are using PostgreSQL v12 to v16 on Debian 10-12 and 
>>> Ubuntu Server 22.04 LTS with no-cluster configuration.
>>> Our applications are developed with 4Js Genero platform (classified 
>>> as LCAP) - https://4js.com
>>>
>>> I whish to report an issue where I can't say if it happens at server 
>>> or client side (or both as well).
>>
>> This:
>>
>> "unexpected EOF on client connection "
>>
>> makes me believe this is on client side.
>>
>> To be clear the client is running on Ubuntu Server 22.04, correct?
>>
>> Have you looked at the OS system log for relevant entries at the time 
>> the error occurs?
>>
>> If so what are they?
>>
>> This only happens in production environment, is there anything in it 
>> that is materially different from where you ran the test below?
>>
>>
>>> Hoping you can help me or address to someone who can do it.
>>> Thanks in advance.
>>> Enrico
>>> -- 
>>>
>>> *Enrico Schenone*
>>> Software Architect
>>>
>>
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com