XML DB Index creation problem

Question

We are facing issues in creating index on XMLTYPE elements. In the below example, when we try to create index on "/PurchaseOrder/LineItems/LineItem/Description" element, its throwing "ORA-29036: This feature is not supported" error. It is allowing us to create index on Description element if we remove "maxOccurs="unbounded" attribute either in "LineItem" element or "Part" element. Please provide pointers on this issue. Below are the sample code for schema, table and index creation.
DECLARE
XMLSCHEMADOC VARCHAR2(32767);
BEGIN
XMLSCHEMADOC := '
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xdb="http://xmlns.oracle.com/xdb"
version="1.0" xdb:storeVarrayAsTable="true">
<xs:element name="PurchaseOrder" type="PurchaseOrderType"/>
<xs:complexType name="PurchaseOrderType">
<xs:sequence>
<xs:element name="Reference" type="ReferenceType"/>
<xs:element name="Actions" type="ActionsType"/>
<xs:element name="Reject" type="RejectionType" minOccurs="0"/>
<xs:element name="Requestor" type="RequestorType"/>
<xs:element name="User" type="UserType"/>
<xs:element name="CostCenter" type="CostCenterType"/>
<xs:element name="ShippingInstructions" type="ShippingInstructionsType"/>
<xs:element name="SpecialInstructions" type="SpecialInstructionsType"/>
<xs:element name="LineItems" type="LineItemsType"/>
</xs:sequence>
</xs:complexType>
<xs:complexType name="LineItemsType">
<xs:sequence>
<xs:element name="LineItem" type="LineItemType" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
<xs:complexType name="LineItemType">
<xs:sequence>
<xs:element name="Description" type="DescriptionType"/>
<xs:element name="Part" type="PartType" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="ItemNumber" type="xs:integer"/>
</xs:complexType>
<xs:complexType name="PartType">
<xs:attribute name="Id">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:minLength value="10"/>
<xs:maxLength value="14"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<xs:attribute name="Quantity" type="moneyType"/>
<xs:attribute name="UnitPrice" type="quantityType"/>
</xs:complexType>
<xs:simpleType name="ReferenceType">
<xs:restriction base="xs:string">
<xs:minLength value="18"/>
<xs:maxLength value="30"/>
</xs:restriction>
</xs:simpleType>
<xs:complexType name="ActionsType">
<xs:sequence>
<xs:element name="Action" maxOccurs="4">
<xs:complexType>
<xs:sequence>
<xs:element name="User" type="UserType"/>
<xs:element name="Date" type="DateType" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
<xs:complexType name="RejectionType">
<xs:all>
<xs:element name="User" type="UserType" minOccurs="0"/>
<xs:element name="Date" type="DateType" minOccurs="0"/>
<xs:element name="Comments" type="CommentsType" minOccurs="0"/>
</xs:all>
</xs:complexType>
<xs:complexType name="ShippingInstructionsType">
<xs:sequence>
<xs:element name="name" type="NameType" minOccurs="0"/>
<xs:element name="address" type="AddressType" minOccurs="0"/>
<xs:element name="telephone" type="TelephoneType" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
<xs:simpleType name="moneyType">
<xs:restriction base="xs:decimal">
<xs:fractionDigits value="2"/>
<xs:totalDigits value="12"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="quantityType">
<xs:restriction base="xs:decimal">
<xs:fractionDigits value="4"/>
<xs:totalDigits value="8"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="UserType">
<xs:restriction base="xs:string">
<xs:minLength value="1"/>
<xs:maxLength value="10"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="RequestorType">
<xs:restriction base="xs:string">
<xs:minLength value="0"/>
<xs:maxLength value="128"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="CostCenterType">
<xs:restriction base="xs:string">
<xs:minLength value="1"/>
<xs:maxLength value="4"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="VendorType">
<xs:restriction base="xs:string">
<xs:minLength value="0"/>
<xs:maxLength value="20"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="PurchaseOrderNumberType">
<xs:restriction base="xs:integer"/>
</xs:simpleType>
<xs:simpleType name="SpecialInstructionsType">
<xs:restriction base="xs:string">
<xs:minLength value="0"/>
<xs:maxLength value="2048"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="NameType">
<xs:restriction base="xs:string">
<xs:minLength value="1"/>
<xs:maxLength value="20"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="AddressType">
<xs:restriction base="xs:string">
<xs:minLength value="1"/>
<xs:maxLength value="256"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="TelephoneType">
<xs:restriction base="xs:string">
<xs:minLength value="1"/>
<xs:maxLength value="24"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="DateType">
<xs:restriction base="xs:date"/>
</xs:simpleType>
<xs:simpleType name="CommentsType">
<xs:restriction base="xs:string">
<xs:minLength value="1"/>
<xs:maxLength value="2048"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="DescriptionType">
<xs:restriction base="xs:string">
<xs:minLength value="1"/>
<xs:maxLength value="256"/>
</xs:restriction>
</xs:simpleType>
</xs:schema>
DBMS_XMLSCHEMA.registerSchema(
     SCHEMAURL => 'purchaseorder1.xsd',
     SCHEMADOC => XMLSCHEMADOC,
          LOCAL => TRUE,
          GENTYPES => TRUE,
          GENTABLES => TRUE,
          genbean => FALSE,
          enablehierarchy => 1,
          force => FALSE);
END;
CREATE TABLE PURCHASEORDER (
PURCHASE_ORDER_ID NUMBER PRIMARY KEY,
PURCHASE_ORDER_CONTENTS XMLType
XMLTYPE COLUMN PURCHASE_ORDER_CONTENTS
XMLSCHEMA "purchaseorder1.xsd"
ELEMENT "PurchaseOrder"
VARRAY PURCHASE_ORDER_CONTENTS."XMLDATA"."LineItems"."LineItem"
STORE AS table ACTION_TABLE
((primary key (NESTED_TABLE_ID, SYS_NC_ARRAY_INDEX$))
organization index overflow);
create index po_lineitem_org_idx on PURCHASEORDER(extractValue(PURCHASE_ORDER_CONTENTS,'/PurchaseOrder/LineItems/LineItem/Description'));

Answer 1

Hi,
Thanks for your reply. Please find below my issues
issue 1 : (index creation using extractvalue)
I am able to create index on Description element if I remove maxoccurs="unbounded" from Part element. I am not able to understand, how i am able to create index if I remove maxoccurs="unbounded" from its sibiling.
issue 2 : (Creating an Index for Direct Access to an Ordered Collection Table)
When i tried to create table i am getting the following error.
SQL> CREATE TABLE PURCHASEORDER (
2 PURCHASE_ORDER_ID NUMBER PRIMARY KEY,
3 PURCHASE_ORDER_CONTENTS XMLType
4 )
5 XMLTYPE COLUMN PURCHASE_ORDER_CONTENTS
6 XMLSCHEMA "purchaseorder1.xsd"
7 ELEMENT "PurchaseOrder"
8 VARRAY PURCHASE_ORDER_CONTENTS."XMLDATA"."LineItems"."LineItem"
9 STORE AS table LINEITEM_TABLE
10 ((primary key (NESTED_TABLE_ID, SYS_NC_ARRAY_INDEX$)))
11 VARRAY PURCHASE_ORDER_CONTENTS."XMLDATA"."LineItems"."LineItem"."Part"
12 STORE AS table PART_TABLE
13 ((primary key (NESTED_TABLE_ID, SYS_NC_ARRAY_INDEX$)));
VARRAY PURCHASE_ORDER_CONTENTS."XMLDATA"."LineItems"."LineItem"."Part"
ERROR at line 11:
ORA-22809: nonexistent attribute
Please provide pointers.