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From: Masahiko Sawada <[email protected]>
To: Andrey Borodin <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Aleksander Alekseev <[email protected]>
Cc: pgsql-hackers <[email protected]>
Cc: Chao Li <[email protected]>
Cc: Dagfinn Ilmari Mannsåker <[email protected]>
Subject: Re: Add uuid_to_base32hex() and base32hex_to_uuid() built-in functions
Date: Thu, 26 Mar 2026 15:01:04 -0700
Message-ID: <CAD21AoDyax67fwjmO3MWh_m5P_5u-x2cEx36M=AJuov_fOTNdw@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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On Thu, Mar 26, 2026 at 10:59 AM Andrey Borodin <[email protected]> wrote:
>
>
>
> > On 26 Mar 2026, at 22:30, Masahiko Sawada <[email protected]> wrote:
> >
> >  Feedback is very welcome.
>
> The patch is fine from my POV.
>
> Please consider these small improvements to the patch. Basically, we reference to formula stated by RFC where possible.
> 0001 is intact.

Thank you for the suggestion. It looks good to me.

I've merged these patches and am going to push barring any objections.

Regards,

-- 
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com


Attachments:

  [text/x-patch] v2-0001-doc-Clarify-collation-requirements-for-base32hex-.patch (2.8K, 2-v2-0001-doc-Clarify-collation-requirements-for-base32hex-.patch)
  download | inline diff:
From 35d321a9e3216052c917b4d1a61b93ecb1414e42 Mon Sep 17 00:00:00 2001
From: Masahiko Sawada <[email protected]>
Date: Thu, 26 Mar 2026 10:17:23 -0700
Subject: [PATCH v2] doc: Clarify collation requirements for base32hex
 sortability.

While fixing the base32hex UUID sortability test in commit
89210037a0a, it turned out that the expected lexicographical order is
only maintained under the C collation (or an equivalent byte-wise
collation). Natural language collations may employ different rules,
breaking the sortability.

This commit updates the documentation to explicitly state that
base32hex is "byte-wise sortable", ensuring users do not fall into the
trap of using natural language collations when querying their encoded
data.

Co-Authored-by: Masahiko Sawada <[email protected]>
Co-Authored-by: Andrey Borodin <[email protected]>
Discussion: https://postgr.es/m/CAD21AoAwX1D6baSGuQXm0mzPXPWB07kgaoaaahjNHHenbdY24A@mail.gmail.com
---
 doc/src/sgml/func/func-binarystring.sgml | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/doc/src/sgml/func/func-binarystring.sgml b/doc/src/sgml/func/func-binarystring.sgml
index 0aaf9bc68f1..dc6b7e57ea7 100644
--- a/doc/src/sgml/func/func-binarystring.sgml
+++ b/doc/src/sgml/func/func-binarystring.sgml
@@ -778,18 +778,26 @@
        <ulink url="https://datatracker.ietf.org/doc/html/rfc4648#section-7">
        RFC 4648 Section 7</ulink>.  It uses the extended hex alphabet
        (<literal>0</literal>-<literal>9</literal> and
-       <literal>A</literal>-<literal>V</literal>) which preserves the lexicographical
-       sort order of the encoded data. The <function>encode</function> function
+       <literal>A</literal>-<literal>V</literal>) which preserves the sort order of
+       the encoded data when compared byte-wise. The <function>encode</function> function
        produces output padded with <literal>'='</literal>, while <function>decode</function>
        accepts both padded and unpadded input. Decoding is case-insensitive and ignores
        whitespace characters.
       </para>
       <para>
-       This format is useful for encoding UUIDs in a compact, sortable format:
+       This format is useful for encoding UUIDs in a compact, byte-wise sortable format:
        <literal>rtrim(encode(uuid_value::bytea, 'base32hex'), '=')</literal>
        produces a 26-character string compared to the standard 36-character
        UUID representation.
       </para>
+      <note>
+       <para>
+        To maintain the lexicographical sort order of the encoded data,
+        ensure that the text is sorted using the C collation
+        (e.g., using <literal>COLLATE "C"</literal>). Natural language
+        collations may sort characters differently and break the ordering.
+       </para>
+      </note>
      </listitem>
     </varlistentry>
 
-- 
2.53.0



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  To: [email protected]
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  Subject: Re: Add uuid_to_base32hex() and base32hex_to_uuid() built-in functions
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