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From: "David G. Johnston" <david.g.johnston@gmail.com>
Date: Thu, 16 Oct 2025 14:40:36 -0400
Message-ID: 
 <CAKFQuwb8Qh2akZKV-yieee-rdVQ0-faZRAzxVvbfw2SdKACXaA@mail.gmail.com>
Subject: Re: BPCHAR description in 8.3. Character Types is misleading and
 incomplete
To: Jeff Davis <pgsql@j-davis.com>
Cc: Sergei Katkovsky <skatkovsky@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>,
	"pgsql-docs@lists.postgresql.org" <pgsql-docs@lists.postgresql.org>
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On Thursday, October 16, 2025, Jeff Davis <pgsql@j-davis.com> wrote:

> On Thu, 2025-10-16 at 08:36 -0400, David G. Johnston wrote:
> > A given value has a finite length and there is just no restriction on
> > what that length is.  All trailing spaces in the input are considered
> > padding for purposes of comparison i.e., manually padding is added by
> > the user as opposed to the system.
>
> I see -- so it means that the padding came from somewhere else (not the
> type).
>

Yeah, your original conclusion this couldn=E2=80=99t be labeled blank-padde=
d seems
to have drawn this confusion.  If padding is indeed noun-like and not
verb-like then calling it blank-padded works ok.  The clarifying text is
then just fine as-is: the comment about any included spaces are
semantically insignificant ties back to calling those spaces =E2=80=9Cpaddi=
ng=E2=80=9D and
thus the type itself remains =E2=80=9Cblank-padded=E2=80=9D in both the and=
 N and non-N
cases.  There isn=E2=80=99t a way to make =E2=80=9Ctrimmed=E2=80=9D a noun =
here but those spaces
are not actually removed/trimmed away.

In short, I would change trimmed to padded in the table.

I=E2=80=99d also add =E2=80=9Cpadding=E2=80=9D here just to actually use th=
e word in its noun form.

=E2=80=A6but trailing spaces are [stored as] semantically insignificant [pa=
dding].

(I thought also about trying to remove the phrase =E2=80=9Csemantically
[in]significant=E2=80=9D altogether but at the moment would rather not touc=
h the
following paragraph.)

If we really have to drive the point home I'd also add a footnote marker to
=E2=80=9Cblank-padded=E2=80=9D and then say in the footnote text (right bel=
ow the table):
A blank-padded value contains zero or more trailing spaces which are
ignored for comparison purposes.  These spaces are also called
=E2=80=9Csemantically insignificant=E2=80=9D.

David J.

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On Thursday, October 16, 2025, Jeff Davis &lt;<a href=3D"mailto:pgsql@j-dav=
is.com">pgsql@j-davis.com</a>&gt; wrote:<br><blockquote class=3D"gmail_quot=
e" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">=
On Thu, 2025-10-16 at 08:36 -0400, David G. Johnston wrote:<br>
&gt; A given value has a finite length and there is just no restriction on<=
br>
&gt; what that length is.=C2=A0 All trailing spaces in the input are consid=
ered<br>
&gt; padding for purposes of comparison i.e., manually padding is added by<=
br>
&gt; the user as opposed to the system.<br>
<br>
I see -- so it means that the padding came from somewhere else (not the<br>
type).<br>
</blockquote><div><br></div><div>Yeah, your original conclusion this couldn=
=E2=80=99t be labeled blank-padded seems to have drawn this confusion.=C2=
=A0 If padding is indeed noun-like and not verb-like then calling it blank-=
padded works ok.=C2=A0 The clarifying text is then just fine as-is: the com=
ment about any included spaces are semantically insignificant ties back to =
calling those spaces =E2=80=9Cpadding=E2=80=9D and thus the type itself rem=
ains =E2=80=9Cblank-padded=E2=80=9D in both the and N and non-N cases.=C2=
=A0 There isn=E2=80=99t a way to make =E2=80=9Ctrimmed=E2=80=9D a noun here=
 but those spaces are not actually removed/trimmed away.</div><div><br></di=
v><div>In short, I would change trimmed to padded in the table.</div><div><=
br></div><div>I=E2=80=99d also add =E2=80=9Cpadding=E2=80=9D here just to a=
ctually use the word in its noun form.</div><div><br></div><div>=E2=80=A6bu=
t trailing spaces are [stored as] semantically insignificant [padding].</di=
v><div><br></div><div>(I thought also about trying to remove the phrase =E2=
=80=9Csemantically [in]significant=E2=80=9D altogether but at the moment wo=
uld rather not touch the following paragraph.)</div><div><br></div><div>If =
we really have to drive the point home I&#39;d also add a footnote marker t=
o =E2=80=9Cblank-padded=E2=80=9D and then say in the footnote text (right b=
elow the table):</div><div>A blank-padded value contains zero or more trail=
ing spaces which are ignored for comparison purposes.=C2=A0 These spaces ar=
e also called =E2=80=9Csemantically insignificant=E2=80=9D.</div><div><br><=
/div><div>David J.</div><div><br></div>

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