Re: Update docs for UUID data type - Mailing list pgsql-hackers

On Sun, 2025-02-23 at 22:23 -0500, Andy Alsup wrote:
> Please find the attached patch files that supersede the previous email. 
>
> Patch 0001 contains some modest modifications to the UUID data type docs
> (Section 8.12. UUID Type). The main goal is to inform the reader that there
> are multiple versions of UUID generation algorithms (presently 8); however,
> once generated, PostgreSQL treats all UUIDs uniformly.
>
> Patch 0002 contains modifications to the UUID functions docs (Section 9.14.
> UUID Functions). The main goal is to format the UUID functions in table form,
> similar to other function docs, such as Section 9.4. String Functions and
> Operators. This provides the user a more consistent format, in line with
> more established sections of the PostgreSQL documentation.
>
> Thank you for your time and consideration.

I had a look at the patches.

About the first patch:

> diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml
> index 87679dc4a11..9841b125e06 100644
> --- a/doc/src/sgml/datatype.sgml
> +++ b/doc/src/sgml/datatype.sgml
> @@ -4399,12 +4399,21 @@ SELECT to_tsvector( 'postgraduate' ), to_tsquery( 'postgres:*' );
>      ISO/IEC 9834-8:2005, and related standards.
>      (Some systems refer to this data type as a globally unique identifier, or
>      GUID,<indexterm><primary>GUID</primary></indexterm> instead.)  This
> -    identifier is a 128-bit quantity that is generated by an algorithm chosen
> -    to make it very unlikely that the same identifier will be generated by
> -    anyone else in the known universe using the same algorithm.  Therefore,
> -    for distributed systems, these identifiers provide a better uniqueness
> -    guarantee than sequence generators, which
> -    are only unique within a single database.
> +    identifier is a 128-bit quantity generated by an algorithm chosen to make it
> +    extremely unlikely that the same identifier will be generated by any other system.
> +    Therefore, for distributed systems, these identifiers offer better uniqueness
> +    guarantees than sequence generators, which only guarantee uniqueness within a
> +    single database.
> +   </para>
> +
> +   <para>
> +    The UUID RFC defines 8 discrete UUID versions. Each version has specific requirements
> +    for generating new UUID values, and each version provides distinct benefits and drawbacks.
> +    PostgreSQL provides native support for generating UUIDs using the UUIDv4 and
> +    UUIDv7 algorithms. Alternatively, UUID values can be generated outside of the
> +    PostgreSQL database using any algorithm. In any case, PostgreSQL supports the
> +    <type>uuid</type> datatype uniformly, regardless of the UUID version or whether it
> +    was generated internally or externally.

"PostgreSQL" should wear a <productname> tag.

Your change to the first paragraph is just the removal of "that is" and
rearranging the line breaks.  I don't think that the wording becomes any
clearer through that change, and it makes reading the patch more difficult.
It is a good idea to change as little as possible in the existing text
(particularly in the line breaks), so that reviewing becomes easier.

About the new paragraph: it should be "different", not "discrete".

I am not certain if the part after "alternatively" adds any relevant
information.  Also, I am not certain what you mean with "uniformly".
Perhaps that sentence could be

  The PostgreSQL data type <type>uuid</type> supports all kinds of UUIDs,
  regardless of their version.

We don't mention that "integer" can be used to store integers generated
inside and outside PostgreSQL, so I don't think we need to mention that
here.

About the second patch:

A table is a good thing.  We typically have an introductory paragraph
before such tables that contains a hyperlink to the table, something like

  <xref ...> shows the <productname>PostgreSQL</productname> functions
  that can be used to generate UUIDs:

Yours,
Laurenz Albe

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