BUG #15155: table_to_xmlschema() ignores string restriction when generating XSD

The following bug has been logged on the website:

Bug reference: 15155
Logged by: Hardy Jonck
Email address: hjonck@gmail.com
PostgreSQL version: 10.3
Operating system: macOS 10.13.2 (17C67b) Kernel Version: Darwin 17
Description:

The *_to_xmlschema() functions correctly export restrictions for other types
but not for string.

For String, it exports and empty
<xsd:restriction base="xsd:string"></xsd:restriction>

To Reproduce:

CREATE DATABASE xsd_test;

\c xsd_test

CREATE TABLE if not exists to_xsd_test
(
_int INT,
_float FLOAT,
_varchar VARCHAR(10),
_date DATE
);

SELECT table_to_xmlschema('to_xsd_test',true,true,'');

Output (see string definition) - expecting a maxLength restriction:

<xsd:schema

xmlns:xsd="http://www.w3.org/2001/XMLSchema&quot;&gt;

<xsd:simpleType name="INTEGER">

<xsd:restriction base="xsd:int">

<xsd:maxInclusive value="2147483647"/>

<xsd:minInclusive value="-2147483648"/>

</xsd:restriction>

</xsd:simpleType>

<xsd:simpleType name="DOUBLE">

<xsd:restriction base="xsd:double"></xsd:restriction>

</xsd:simpleType>

<xsd:simpleType name="VARCHAR">

<xsd:restriction base="xsd:string">

</xsd:restriction>

</xsd:simpleType>

<xsd:simpleType name="DATE">

<xsd:restriction base="xsd:date">

<xsd:pattern value="\p{Nd}{4}-\p{Nd}{2}-\p{Nd}{2}"/>

</xsd:restriction>

</xsd:simpleType>

<xsd:complexType name="RowType.xsd_test.public.to_x005F_xsd_test">

<xsd:sequence>

<xsd:element name="_int" type="INTEGER" nillable="true"></xsd:element>

<xsd:element name="_float" type="DOUBLE" nillable="true"></xsd:element>

<xsd:element name="_varchar" type="VARCHAR"
nillable="true"></xsd:element>
<xsd:element name="_date" type="DATE" nillable="true"></xsd:element>

</xsd:sequence>

</xsd:complexType>

<xsd:element name="to_x005F_xsd_test"
type="RowType.xsd_test.public.to_x005F_xsd_test"/>

</xsd:schema>