[pgpool-general: 9387] Re: [EXTERNAL] Re: PostgreSQL: 25001: DISCARD ALL cannot be executed within a pipeline

[Truijen, Martien]

Mr. Tatsuo Ishi,

Thank you for your quick response.

We see a very clear difference between v4.5.2 and v4.5.4.
In v4.5.2, queries are consistently failing with the "DISCARD ALL cannot be executed within a pipeline". However, when using v4.5.4, all these errors have disappeared.

We use Npgsql v4.0.13 on the Microsoft Data Gateway (Power BI Gateway). Do you happen to know of any issues reported with this version of Npgsql?

Thank you in advance,

Martien Truijen
Fluke Corporation
Everett, WA USA



-----Original Message-----
From: Tatsuo Ishii <ishii at postgresql.org>
Sent: Wednesday, March 5, 2025 1:04 AM
To: Truijen, Martien <martien.truijen at fluke.com>
Cc: pgpool-general at pgpool.net
Subject: [EXTERNAL] Re: [pgpool-general: 9385] PostgreSQL: 25001: DISCARD ALL cannot be executed within a pipeline

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> With Pgpool-II 4.5.2, we had a lot of reports from users that reports were failing with "PostgreSQL: 25001: DISCARD ALL cannot be executed within a pipeline" .
> We upgraded to 4.5.4 with the hope that it would fix the issue. There was no obvious release note that was indicating that it would fix the issue.
> Luckily version 4.5.4 is no longer throwing this error.
>
> My question here is, what specific bug was fixed in 4.5.3 or 4.5.4 that could have fixed  this issue.
> Any help would be greatly appreciated.

It's not fixed because it is not a bug of Pgpool-II IMO. Actually it's caused by client's (or driver's) bug. In this case the client initiates an extended query protocol. In the protocol, the client should send "Sync" message at the end of command (thus before exiting the session) but when the error appears the client did not send Sync, which is not a good behavior from the protocol's point of view:

https://urldefense.com/v3/__https://www.postgresql.org/docs/17/protocol-flow.html*PROTOCOL-FLOW-EXT-QUERY__;Iw!!KPww_GFiJXw!aIKG6j6Vt6iOMwRbb4pKYEIVdgXB5jooOc7OOnGkID1t9SgwGpyhYdvaiwD9hCgcDFUFkBrgV3he6EzyPBGZXw$

"At completion of each series of extended-query messages, the frontend should issue a Sync message."

I suggest to fix the client (or driver).

Best reagards,
--
Tatsuo Ishii
SRA OSS K.K.
English: https://urldefense.com/v3/__http://www.sraoss.co.jp/index_en/__;!!KPww_GFiJXw!aIKG6j6Vt6iOMwRbb4pKYEIVdgXB5jooOc7OOnGkID1t9SgwGpyhYdvaiwD9hCgcDFUFkBrgV3he6Eyw_4ltlw$
Japanese:https://urldefense.com/v3/__http://www.sraoss.co.jp__;!!KPww_GFiJXw!aIKG6j6Vt6iOMwRbb4pKYEIVdgXB5jooOc7OOnGkID1t9SgwGpyhYdvaiwD9hCgcDFUFkBrgV3he6ExFRJejCA$
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