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From: surya poondla <suryapoondla4@gmail.com>
Date: Tue, 10 Feb 2026 13:51:11 -0800
Message-ID: <CAOVWO5oT0x9snrGFPgoWc+-2sBcYSgm+aU=DbiZHWM_HXTbfYg@mail.gmail.com>
Subject: Re: Possibly a bug
To: jian he <jian.universality@gmail.com>
Cc: =?UTF-8?B?0JDQvdCw0YLQvtC70LjQuQ==?= <anatoly@email.su>, 
	pgsql-bugs@lists.postgresql.org
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Hi Jian,

These current.* functions always use the "C" collation for their
> output, so in this case, they are not related to session variables, in
> my view.
>

Thank you, I did some more testing and see the below.

postgres=3D# SELECT collation for (user);
 pg_collation_for
------------------
 "C"
(1 row)

postgres=3D# SELECT collation for (current_user);
 pg_collation_for
------------------
 "C"
(1 row)

postgres=3D#   SELECT to_upper_varchar('=D1=82=D0=B5=D1=81=D1=82'::varchar)=
;
 to_upper_varchar
------------------
 =D0=A2=D0=95=D0=A1=D0=A2
(1 row)

postgres=3D#   SELECT collation for ('=D1=82=D0=B5=D1=81=D1=82');
 pg_collation_for
------------------

(1 row)

postgres=3D#   CREATE OR REPLACE FUNCTION debug_func(param1 text, param2
text) RETURNS text AS $$ SELECT 'param1 collation: ' ||
pg_collation_for(param1) || ', param2 collation: ' ||
pg_collation_for(param2); $$ LANGUAGE sql;
CREATE FUNCTION
postgres=3D#   SELECT debug_func('=D1=82=D0=B5=D1=81=D1=82', user::text);
                 debug_func
----------------------------------------------
 param1 collation: "C", param2 collation: "C"
(1 row)

postgres=3D#   CREATE OR REPLACE FUNCTION debug_func2(param1 text, param2
text) RETURNS text AS $$ SELECT 'param1 collation: ' ||
pg_collation_for(param1) || ', param2 collation: ' ||
pg_collation_for(param2); $$ LANGUAGE sql;
CREATE FUNCTION
postgres=3D# SELECT debug_func2('=D1=82=D0=B5=D1=81=D1=82'::text, user::tex=
t);
                  debug_func2
----------------------------------------------
 param1 collation: "C", param2 collation: "C"
(1 row)

postgres=3D#

My observation is the user, current* functions collation is "C" collation
and when a "C" collation is passed as a parameter, it converts all the
parameters to use the "C" collation.

I was looking at sql_fn_make_param() function and the comments over their
say
"/*
* If we have a function input collation, allow it to override the
* type-derived collation for parameter symbols.  (XXX perhaps this should
* not happen if the type collation is not default?)
*/
"
From the above code comment it looks like the "C" collation is overriding
the type-driven collation, and this might be causing the issue.

I am currently using gdb to debug more and will work on a patch based on my
findings.

Regards,
Surya Poondla

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<div dir=3D"ltr"><div dir=3D"ltr">Hi Jian,</div><div dir=3D"ltr"><br></div>=
<div class=3D"gmail_quote gmail_quote_container"><blockquote class=3D"gmail=
_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204=
,204);padding-left:1ex">
These current.* functions always use the &quot;C&quot; collation for their<=
br>
output, so in this case, they are not related to session variables, in<br>
my view.<br></blockquote><div><br>Thank you, I did some more testing and se=
e the below.</div><div><br></div><div>postgres=3D# SELECT collation for (us=
er);<br>=C2=A0pg_collation_for<br>------------------<br>=C2=A0&quot;C&quot;=
<br>(1 row)<br><br>postgres=3D# SELECT collation for (current_user);<br>=C2=
=A0pg_collation_for<br>------------------<br>=C2=A0&quot;C&quot;<br>(1 row)=
<br><br></div><div>postgres=3D# =C2=A0 SELECT to_upper_varchar(&#39;=D1=82=
=D0=B5=D1=81=D1=82&#39;::varchar);<br>=C2=A0to_upper_varchar<br>-----------=
-------<br>=C2=A0=D0=A2=D0=95=D0=A1=D0=A2<br>(1 row)<br><br>postgres=3D# =
=C2=A0 SELECT collation for (&#39;=D1=82=D0=B5=D1=81=D1=82&#39;);<br>=C2=A0=
pg_collation_for<br>------------------<br><br>(1 row)</div><div><br></div><=
div>postgres=3D# =C2=A0 CREATE OR REPLACE FUNCTION debug_func(param1 text, =
param2 text) RETURNS text AS $$ SELECT &#39;param1 collation: &#39; || pg_c=
ollation_for(param1) || &#39;, param2 collation: &#39; || pg_collation_for(=
param2); $$ LANGUAGE sql;<br>CREATE FUNCTION<br>postgres=3D# =C2=A0 SELECT =
debug_func(&#39;=D1=82=D0=B5=D1=81=D1=82&#39;, user::text);<br>=C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0debug_func<br>---------=
-------------------------------------<br>=C2=A0param1 collation: &quot;C&qu=
ot;, param2 collation: &quot;C&quot;<br>(1 row)<br><br>postgres=3D# =C2=A0 =
CREATE OR REPLACE FUNCTION debug_func2(param1 text, param2 text) RETURNS te=
xt AS $$ SELECT &#39;param1 collation: &#39; || pg_collation_for(param1) ||=
 &#39;, param2 collation: &#39; || pg_collation_for(param2); $$ LANGUAGE sq=
l;<br>CREATE FUNCTION<br>postgres=3D# SELECT debug_func2(&#39;=D1=82=D0=B5=
=D1=81=D1=82&#39;::text, user::text);<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
 =C2=A0 =C2=A0 =C2=A0 =C2=A0 debug_func2<br>-------------------------------=
---------------<br>=C2=A0param1 collation: &quot;C&quot;, param2 collation:=
 &quot;C&quot;<br>(1 row)<br><br>postgres=3D#</div><div><br></div><div>My o=
bservation is the user, current* functions collation=C2=A0is &quot;C&quot; =
collation and when a &quot;C&quot; collation is passed as a parameter, it c=
onverts all the parameters to use the &quot;C&quot; collation.<br><br>I was=
 looking at=C2=A0sql_fn_make_param() function and the comments over their s=
ay<br>&quot;/*</div>	 * If we have a function input collation, allow it to =
override the<br>	 * type-derived collation for parameter symbols. =C2=A0(XX=
X perhaps this should<br>	 * not happen if the type collation is not defaul=
t?)<br>	 */<br>&quot;<br>From the above code comment it looks like the &quo=
t;C&quot; collation is overriding the type-driven collation, and this might=
 be causing the issue.<br><br>I am currently using gdb to debug more and wi=
ll work on a patch based on my findings.</div><div class=3D"gmail_quote gma=
il_quote_container"><br></div><div class=3D"gmail_quote gmail_quote_contain=
er">Regards,<br>Surya Poondla</div></div>

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