XPath query rewrite and insertChildXML (10g2): Help?

Question

Hi all,
I have a registered schema for a <log> document. The schema defines an element /log/logData and under that there, /log/logData/data having maxOccurs="unbounded". So the form of documents is
<log>
<logData>
<data>a</data>
<data>b</data>
<data>c</data>
</logData>
</log>
In the schema definition I have enabled "storeArrayAsVArray='true'". The <data> elements are stored in a nested table. Every type is stored object-relationally.
To an instance documen, I add <data> elements so:
UPDATE log SET object_value = insertChildXML(object_value, 'log/logData', 'data', '<data>foo</data>') WHERE existsNode ('/log[@uid="foo"]')
The call succeeds but the problem is that I need to make this call thousands of times. Initiallly the call might take 100 ms, but after a few hundred inserts inserting a single element takes over a second, and the time keeps increasing.
I believe at least part of the problem is that XPath query rewrites are not working for this call.
Following Chapter 6 of Oracle XML DB Developer's Guide, to debug the problem I have switched on
ALTER SESSION SET EVENTS '19021 trace name context forever, level 1';
and then every invocation causes:
ORA-19022: XML XPath functions are disabled
indicating that Oracle could not rewrite the query. Then I set
ALTER SESSION SET EVENTS '19027 TRACE NAME CONTEXT FOREVER, LEVEL 8192'
to obtain a trace file. Here is a portion of that trace:
*** 2005-10-30 16:54:44.984
*** ACTION NAME:() 2005-10-30 16:54:44.968
*** MODULE NAME:(SQL*Plus) 2005-10-30 16:54:44.968
*** SERVICE NAME:(SYS$USERS) 2005-10-30 16:54:44.968
*** SESSION ID:(137.38364) 2005-10-30 16:54:44.968
NO REWRITE
     Reason ==> xseq:not optuop
NO REWRITE
     Reason ==> xseq:not optuop
NO REWRITE
     Reason ==> not SQLX operand
NO REWRITE
     Reason ==> non sqlx expression input
NO REWRITE
     Reason ==> non rewritable sqlx input
NO REWRITE
(the rest of the file repeats these lines)
I have no idea how to interpet that! Can anyone out there offer some insight/assistance?
Thanks if you can,
Hugh

Answer 1

Below is a complete example script. Cannot seem to get rewrite for even this simple case. By that I mean, executing both of the SELECT statements near the end yield the ORA-19022, and that executing the insertChildXML takes progressively longer to execute the more child elements there are.
Any pointers appreciated!
Hugh
set echo on
ALTER SESSION SET EVENTS '19021 trace name context forever, level 1';
ALTER SESSION SET EVENTS '19027 TRACE NAME CONTEXT FOREVER, LEVEL 8192';
exec dbms_xmlschema.deleteSchema('http://hughw.net/foo', dbms_xmlschema.DELETE_CASCADE_FORCE);
begin
dbms_xmlschema.registerSchema('http://hughw.net/foo', XMLType('<?xml version="1.0" encoding="UTF-8"?>
<xs:schema targetNamespace="http://hughw.net/foo" xmlns="http://hughw.net/foo" xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" attributeFormDefault="unqualified"
xmlns:xdb="http://xmlns.oracle.com/xdb" xdb:storeVarrayAsTable="true">
<xs:element name="root" xdb:defaultTable="ROOT" >
<xs:complexType xdb:SQLType="ROOT_T">
<xs:sequence>
<!-- could use out of line storage -->
<!-- commented out
<xs:element name="child" type="childType" minOccurs="0" maxOccurs="unbounded"
xdb:SQLName="CHILDREN"
xdb:SQLInline="false" xdb:defaultTable="CHILD"
/>
-->
<!-- use nested table -->
<xs:element name="child" type="childType" minOccurs="0" maxOccurs="unbounded"
xdb:SQLName="CHILDREN"
xdb:SQLCollType="CHILD_V"
/>
</xs:sequence>
<xs:attribute name="uid" type="xs:string" use="required"/>
</xs:complexType>
</xs:element>
<xs:complexType name="childType" xdb:SQLType="CHILD_T">
<xs:simpleContent>
<xs:extension base="xs:string"/>
</xs:simpleContent>
</xs:complexType>
</xs:schema>'));
end;
insert into root values( XMLType('<?xml version="1.0" encoding="UTF-8"?>
<root uid="1" xmlns="http://hughw.net/foo"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://hughw.net/foo http://hughw.net/foo">
<child>a</child>
<child>b</child>
<child>c</child>
</root>'));
CREATE INDEX ROOT_INDEX ON ROOT (extractValue(object_value,'/root/@uid'));
select insertChildXML(object_value, '/root', 'child', '<child>x</child>>') FROM root;
explain plan for select insertChildXML(object_value, '/root', 'child', '<child>x</child>>') FROM root;
SELECT PLAN_TABLE_OUTPUT FROM table(DBMS_XPLAN.display('plan_table', NULL, 'serial'));
select insertChildXML(object_value, '/root', 'child', '<child>x</child>>') FROM root
WHERE existsNode(object_value, '/root[@uid="1"]') = 1;
explain plan for select insertChildXML(object_value, '/root', 'child', '<child>x</child>>') FROM root
WHERE existsNode(object_value, '/root[@uid="1"]') = 1;
SELECT PLAN_TABLE_OUTPUT FROM table(DBMS_XPLAN.display('plan_table', NULL, 'serial'));