Message-ID: <37c6dcd199f3dfa41fc51ce347687210fd372363.camel@cybertec.at>
Subject: Re: Understanding DateStyle guc in startup packet
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Manav Kumar <mkumar@yugabyte.com>, Vladimir Sitnikov
	 <sitnikov.vladimir@gmail.com>
Cc: pgsql-jdbc@lists.postgresql.org
Date: Fri, 23 May 2025 11:58:51 +0200
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On Fri, 2025-05-23 at 14:08 +0530, Manav Kumar wrote:
> Can you also share how=C2=A0does DRIVER comes to know the value been set =
for
> DateStyle is other than "ISO". and throw an error:
> =C2=A0The server's DateStyle parameter was changed to Postgres, DMY. The =
JDBC driver requires DateStyle to begin with ISO for correct operation.=C2=
=A0
>=20
> I thought it used to read the PARAMETER STATUS packet that it receives
> from the server. But I tried changing it connection pooler i doens't
> see the same error. Can you point me to code where this assert check
> is present.=C2=A0=C2=A0

See the method
org.postgresql.core.v3.QueryExecutorImpl.receiveParameterStatus()
https://github.com/pgjdbc/pgjdbc/blob/master/pgjdbc/src/main/java/org/postg=
resql/core/v3/QueryExecutorImpl.java#L2886

See the PostgreSQL documentation for context:
https://www.postgresql.org/docs/current/protocol-flow.html#PROTOCOL-ASYNC

  ParameterStatus messages will be generated whenever the active value
  changes for any of the parameters the backend believes the frontend
  should know about. Most commonly this occurs in response to a SET SQL
  command executed by the frontend, and this case is effectively
  synchronous =E2=80=94 but it is also possible for parameter status change=
s
  to occur because the administrator changed a configuration file and
  then sent the SIGHUP signal to the server. Also, if a SET command is
  rolled back, an appropriate ParameterStatus message will be generated
  to report the current effective value.

Yours,
Laurenz Albe