docs - update ENUM type can have zero labels.
This will be backported to 6X_STABLE
@@ -43,8 +43,8 @@ schema. Otherwise it is created in the current schema. The type name
must be distinct from the name of any existing type or domain in the
same schema. The type name must also be distinct from the name of any
existing table in the same schema.</p>
- <p>There are five forms of CREATE TYPE, as shown in the syntax synopsis above. They
- respectively create a <i>composite type</i>, an <i>enum type</i>, a <i>range
+ <p>There are five forms of <codeph>CREATE TYPE</codeph>, as shown in the syntax synopsis
+ above. They respectively create a <i>composite type</i>, an <i>enum type</i>, a <i>range
type</i>, a <i>base type</i>, or a <i>shell type</i>. The first four of these
are discussed in turn below. A shell type is simply a placeholder for a type to be
defined later; it is created by issuing <codeph>CREATE TYPE</codeph> with no
@@ -61,10 +61,13 @@ existing table in the same schema.</p>
create a composite type, you must have <codeph>USAGE</codeph> privilege on all
attribute types.</p></sectiondiv>
<sectiondiv id="enum"><b>Enumerated Types</b>
-<p>The second form of <codeph>CREATE TYPE</codeph> creates an enumerated (<codeph>ENUM</codeph>) type, as described in
-<xref href="https://www.postgresql.org/docs/8.3/datatype-enum.html" format="html" scope="external">Enumerated Types</xref> in the
-PostgreSQL documentation. Enum types take a list of one or more quoted labels, each of which must be less than
-<codeph>NAMEDATALEN</codeph> bytes long (64 in a standard build).</p>
+ <p>The second form of <codeph>CREATE TYPE</codeph> creates an enumerated
+ (<codeph>ENUM</codeph>) type, as described in <xref href="https://www.postgresql.org/docs/8.3/datatype-enum.html" format="html" scope="external">Enumerated Types</xref> in the PostgreSQL documentation.
+ <codeph>ENUM</codeph> types take a list of quoted labels, each of which must
+ be less than <codeph>NAMEDATALEN</codeph> bytes long (64 in a standard
+ build).</p><p>It is possible to create an enumerated type with zero labels, but
+ such a type cannot be used to hold values before at least one label is added
+ using <xref href="ALTER_TYPE.xml"/>.</p>
</sectiondiv>
<sectiondiv><b>Range Types</b><p>The third form of <codeph>CREATE TYPE</codeph> creates a
new range type, as described in <xref href="../datatype-range.xml#rangetypes"
