Merge pull request #9210 from alexander-schranz/patch-2

Fix making columns  optional in indexes xml schema as they can be defined via fields now

Author: alexander-schranz

doctrine-mapping.xsd

@@ -353,7 +353,7 @@
       <xs:any minOccurs="0" maxOccurs="unbounded" namespace="##other"/>
     </xs:choice>
     <xs:attribute name="name" type="xs:NMTOKEN" use="optional"/>
-    <xs:attribute name="columns" type="xs:string" use="required"/>
+    <xs:attribute name="columns" type="xs:string" use="optional"/>
     <xs:attribute name="fields" type="xs:string" use="optional"/>
     <xs:attribute name="flags" type="xs:string" use="optional"/>
     <xs:anyAttribute namespace="##other"/>