Updatable cursor support in pg-gpdb feature differences chart. (#2031)

gpdb-doc/dita/ref_guide/feature_summary.xml

@@ -564,15 +564,16 @@ NEXT 10 ROWS ONLY; </codeblock><p>Greenplum
               <entry colname="col1"><codeph>DECLARE</codeph></entry>
               <entry colname="col2">YES</entry>
               <entry colname="col3"><b>Unsupported Clauses /
-                  Options:</b><p><codeph>SCROLL</codeph></p><p><codeph>FOR UPDATE [ OF column [,
-                    ...] ]</codeph></p><p><b>Limitations:</b></p><p>Cursors are non-updatable, and
-                  cannot be backward-scrolled. Forward scrolling is supported.</p></entry>
+                  Options:</b><p><codeph>SCROLL</codeph></p><p><b>Limitations:</b></p><p>Cursors
+                  cannot be backward-scrolled. Forward scrolling is supported. </p><p>PL/pgSQL does
+                  not have support for updatable cursors. </p></entry>
             </row>
             <row>
               <entry colname="col1"><codeph>DELETE</codeph></entry>
               <entry colname="col2">YES</entry>
               <entry colname="col3"><b>Unsupported Clauses /
-                    Options:</b><p><codeph>RETURNING</codeph></p></entry>
+                    Options:</b><p><codeph>RETURNING</codeph></p><p><b>Limitations:</b></p><p><codeph>WHERE
+                    CURRENT OF</codeph> clause is not supported in PL/pgSQL.</p></entry>
             </row>
             <row>
               <entry colname="col1"><codeph>DROP AGGREGATE</codeph></entry>
@@ -890,7 +891,8 @@ NEXT 10 ROWS ONLY; </codeblock><p>Greenplum
               <entry colname="col2">YES</entry>
               <entry colname="col3"><b>Unsupported
                     Clauses:</b><p><codeph>RETURNING</codeph></p><p><b>Limitations:</b></p><p><codeph>SET</codeph>
-                  not allowed for Greenplum distribution key columns.</p></entry>
+                  not allowed for Greenplum distribution key columns.</p><p><codeph>WHERE CURRENT
+                    OF</codeph> clause is not supported in PL/pgSQL.</p></entry>
             </row>
             <row>
               <entry colname="col1"><codeph>VACUUM</codeph></entry>