Xml select query performance

Question

the table i have
create table test of xmltype;
and the xml that i have loaded is
<root>
     <company>
<department>
<id>10</id>
<name>Accounting</name>
</department>
<department>
<id>11</id>
<name>Billing</name>
</department>
</company>
     </root>
select query using xmltable is
select id,name from test,xmltable('/root/company/department'
passing object_value
columns
id number path 'id',
name varchar2(20) 'name');
the query is working fine but issue is performance
i have imlplemented index using extract() and extractstringval() functions but as i have multiple
occurance of data ther two are not working. I have non-schema-based xmltype table.
I need help for creating index on multiple occurance element
Any help is appreciated

Answer 1

First of all "XMLOptimizationCheck" AFAIK is not yet explained. Haven't checked support.oracle.com for a while though.
It's more or less currently an internal used, but for the public a fast method to detect, that Oracle internal XQuery / XPath optimization rewrites towards SQL methods (shortcuts) are not properly working. SYS_XQEXVAL probably means something like XQuery Element XML Value/validation (??? towards SQL value) isn't producing a simple construct with a predicate validation. The reasons section gives insight, just like a 10053 trace, on what attempts/rules where applied and failed or worked. I am guessing that the overall cost for the use of the normal PK index is so high because it can not be properly matched and/or optimized against the global index structure supporting the partitions.
In all, a bit more info regarding the table/partition structure and its used index regime/structure would be helpful.
Beside that. THIS IS A BUG and should be reported, request for help, via support.oracle.com
Edited by: Marco Gralike on Mar 23, 2011 9:35 PM