doc: Update SQL features/conformance information to SQL:2023

Optional subfeatures have been changed to top-level features, so there
is a bit of a churn in the list for that.

Some existing functions have been added to the standard, so they are
moved from the "other" to the "standard" lists in their sections.

Discussion: https://www.postgresql.org/message-id/flat/63f285d9-4ec8-0c9e-4bf5-e76334ddc0af@enterprisedb.com

Author: petere

doc/src/sgml/datatype.sgml

@@ -1242,8 +1242,7 @@ SELECT '52093.89'::money::numeric::float8;
     than zero and cannot exceed 10485760.
     <type>character</type> without length specifier is equivalent to
     <type>character(1)</type>. If <type>character varying</type> is used
-    without length specifier, the type accepts strings of any size. The
-    latter behavior is a <productname>PostgreSQL</productname> extension.
+    without length specifier, the type accepts strings of any size.
    </para>
 
    <para>

doc/src/sgml/features.sgml

@@ -14,9 +14,9 @@
  <para>
   The formal name of the SQL standard is ISO/IEC 9075 <quote>Database
   Language SQL</quote>.  A revised version of the standard is released
-  from time to time; the most recent update appearing in 2016.
-  The 2016 version is referred to as ISO/IEC 9075:2016, or simply as SQL:2016.
-  The versions prior to that were SQL:2011, SQL:2008, SQL:2006, SQL:2003,
+  from time to time; the most recent update appearing in 2023.
+  The 2023 version is referred to as ISO/IEC 9075:2023, or simply as SQL:2023.
+  The versions prior to that were SQL:2016, SQL:2011, SQL:2008, SQL:2006, SQL:2003,
   SQL:1999, and SQL-92.  Each version
   replaces the previous one, so claims of conformance to earlier
   versions have no official merit.
@@ -62,6 +62,7 @@
    <listitem><para>ISO/IEC 9075-13 Routines and Types using the Java Language (SQL/JRT)</para><indexterm><primary>SQL/JRT</primary></indexterm></listitem>
    <listitem><para>ISO/IEC 9075-14 XML-related specifications (SQL/XML)</para><indexterm><primary>SQL/XML</primary></indexterm></listitem>
    <listitem><para>ISO/IEC 9075-15 Multi-dimensional arrays (SQL/MDA)</para><indexterm><primary>SQL/MDA</primary></indexterm></listitem>
+   <listitem><para>ISO/IEC 9075-16 Property Graph Queries (SQL/PGQ)</para><indexterm><primary>SQL/PGQ</primary></indexterm></listitem>
   </itemizedlist>
 
   Note that some part numbers are not (or no longer) used.
@@ -72,23 +73,23 @@
   11, and 14.  Part 3 is covered by the ODBC driver, and part 13 is
   covered by the PL/Java plug-in, but exact conformance is currently
   not being verified for these components.  There are currently no
-  implementations of parts 4, 10, and 15
+  implementations of parts 4, 10, 15, and 16
   for <productname>PostgreSQL</productname>.
  </para>
 
  <para>
-  PostgreSQL supports most of the major features of SQL:2016.  Out of
+  PostgreSQL supports most of the major features of SQL:2023.  Out of
   177 mandatory features required for full Core conformance,
   PostgreSQL conforms to at least 170.  In addition, there is a long
   list of supported optional features.  It might be worth noting that at
   the time of writing, no current version of any database management
-  system claims full conformance to Core SQL:2016.
+  system claims full conformance to Core SQL:2023.
  </para>
 
  <para>
   In the following two sections, we provide a list of those features
   that <productname>PostgreSQL</productname> supports, followed by a
-  list of the features defined in <acronym>SQL:2016</acronym> which
+  list of the features defined in <acronym>SQL:2023</acronym> which
   are not yet supported in <productname>PostgreSQL</productname>.
   Both of these lists are approximate: There might be minor details that
   are nonconforming for a feature that is listed as supported, and
@@ -135,7 +136,7 @@
    <title>Unsupported Features</title>
 
    <para>
-    The following features defined in <acronym>SQL:2016</acronym> are not
+    The following features defined in <acronym>SQL:2023</acronym> are not
     implemented in this release of
     <productname>PostgreSQL</productname>. In a few cases, equivalent
     functionality is available.