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From: Srinath Reddy Sadipiralla <srinath2133@gmail.com>
Date: Wed, 10 Dec 2025 22:10:02 +0530
Message-ID: <CAFC+b6q7xFQN=wRP0rOCLat=rWNNNhuhEKOUV-2BJ9HxU5SrAQ@mail.gmail.com>
Subject: Re: BUG #19351: in pg18.1,when not null exists in the table , and add
 constraint problem.
To: msdnchina@163.com, pgsql-bugs@lists.postgresql.org
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On Wed, Dec 10, 2025 at 9:32=E2=80=AFPM Srinath Reddy Sadipiralla <
srinath2133@gmail.com> wrote:

> why it's not treated as normal
> constraint and why we are not throwing an error
> like the constraint already exists?
>

ah... just after a quick code lookup, remembered that
"not null" is treated as a column property, which is a
flag in pg_attribute catalog table named as "attnotnull",
i guess the reason(s) it's a column property rather than
constraint might be an overkill, adds overhead of entries
in pg_constraint, or historical reasons, please correct me
if i am wrong, still the right way of setting this constraint "ALTER TABLE
test_null_20251210 ALTER COLUMN c1 SET NOT NULL;"
not throwing an error; i think it makes sense to throw an
error here, thoughts?

--=20
Thanks,
Srinath Reddy Sadipiralla
EDB: https://www.enterprisedb.com/

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote g=
mail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, Dec 10,=
 2025 at 9:32=E2=80=AFPM Srinath Reddy Sadipiralla &lt;<a href=3D"mailto:sr=
inath2133@gmail.com">srinath2133@gmail.com</a>&gt; wrote:</div><blockquote =
class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px sol=
id rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr"><div>why it&#39;s no=
t treated as normal<br>constraint and why we are not throwing an error<br>l=
ike the constraint already exists?</div></div></blockquote><div><br>ah... j=
ust after a quick code lookup, remembered that<br>&quot;not=C2=A0null&quot;=
 is treated as a column property, which is a<br>flag in pg_attribute catalo=
g table named as &quot;attnotnull&quot;,<br>i guess the reason(s) it&#39;s =
a column property rather than<br>constraint might be an overkill, adds over=
head of entries<br>in pg_constraint, or historical reasons, please correct =
me<br>if i am wrong, still the right way of setting this constraint &quot;A=
LTER TABLE test_null_20251210 ALTER COLUMN c1 SET NOT NULL;&quot;<br>not th=
rowing an error; i think it makes sense to throw an<br>error here, thoughts=
?</div></div><div><br></div><span class=3D"gmail_signature_prefix">-- </spa=
n><br><div dir=3D"ltr" class=3D"gmail_signature"><div dir=3D"ltr"><span sty=
le=3D"color:rgb(34,34,34)">Thanks,</span><br style=3D"color:rgb(34,34,34)">=
<span style=3D"color:rgb(34,34,34)">Srinath Reddy Sadipiralla</span><br sty=
le=3D"color:rgb(34,34,34)"><span style=3D"color:rgb(34,34,34)">EDB:=C2=A0</=
span><a href=3D"https://www.enterprisedb.com/" style=3D"color:rgb(17,85,204=
)" target=3D"_blank">https://www.enterprisedb.com/</a></div></div></div>

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