1. XML Indexing Strategies
Choosing the Right Index for the
Right Job
Marco Gralike

2. Strange Chainsaw Tree Guy
• OakTable Member
• ACE Director
• Customer Advisory
Board Member
• 17+ years DBA, etc.
Blog.gralike.com
Technology.amis.nl

3. Richard Foote (Mr. Index)
• OakTable Member
• ACE Director
• Oracle Certified
Professional
• 22+ years DBA, etc.
RichardFoote.wordpress.com

4. Refinement

5. Structured or Semi-Structured or…
Structured
Semi
Structured

6. Unstructured Content

7. Document Driven / Data Driven

8. XML Container
(in memory or via storage)
In Memory
(document)
CLOB
(document)
Object Relational
(data)
Binary XML
(data)

9. Design: Width and Height and …
Z
X
Y
1
2
3
4
6
5
Content Height : minOccurs="0" maxOccurs=“unbounded”
Content Width : type="xs:string“, restriction…?
Content Distribution : histogram, statistics, skew, cardinality ?

11. XMLIndex Use Cases
Binary XML
(Schema based)
XMLIndex
Structured
Component
Binary XML / CLOB Column
(Schema less, Schema
based)
XMLIndex Structured
Component
Mixed
w/ Text
index

12. Storage Models (xmltype)
• CLOB
– Default until 11.2.0.2.0
– Non-Schema Based
• Binary XML
– Oracle 11 and Onwards
– Schema and Non-Schema Based
• Object Relational (+Hybrid)
– Nested Tables, Types, Varray’s
– Schema Based

13. Querying XML Content in XML DB
XMLIndex
DOM Tree
Model
Streaming XPath
Evaluation
Object-Relational
Relational Storage Secure Files
Binary XML
XQuerySQL/XML
XMLType Abstraction
XVM
(use “no query rewrite”)
PushdownXQuery Rewrite
Procedural XQueryDB XQuery
SQL Execution
Relational
Access
Methods
Source: S317428: Building Really Scalable XML Applications with Oracle XML DB and Oracle Text

14. Index Methods (xmltype)

15. Storage Index Defaults (xmltype)
• Binary XML / CLOB
– LOB Index
• Object Relational
– DBMS_XMLSCHEMA  “OPTIONS”
– Oracle 10g: Index Organized Tables
– Oracle 11g: B-Tree Indexes
– xdb:annotations
• Storage type  xdb:SQLType
• Storage Type  xdb:ColumnProps / xdb:TableProps

16. Index Methods (10.x)
paragraph
book
title author author
whitepaper
title author id
content
bookstore
chapter
content
Function
based Index
(XPath)
Oracle Text Index
BTBTre
e I
BTre
e
Index

17. Function-Based Index
• Deprecated in 11.2
• Object Relational XMLType Storage
(can, but shouldn’t on CLOB)
• Performance wise the lesser option…
SQL> CREATE INDEX function_based_index
ON xml_data_table
(extractValue(OBJECT_VALUE, '/Root/TextID'));

18. BTree / Bitmap Index
• Structured XML Data
– Ordered Collection Tables (OCT)
– ComplexTypes…
– “dot” notation using the “xmldata” pseudocolumn
SQL> CREATE INDEX dot_notation_index
ON xml_data_table
("XMLDATA". "TEXTID");

19. Index Alternatives
SQL> CREATE INDEX oracle_11_applicable_only_index
ON xml_data_table xdt
(XMLCast(XMLQuery
('$i/Root/TextID'
PASSING xdt.OBJECT_VALUE as "i"
RETURNING content)
as VARCHAR2(10)));
SQL> CREATE INDEX function_based_again_idx
ON xml_data_table
(CAST("XMLDATA". "TEXTID“ as VARCHAR2(10)));

20. Oracle Text Index
• Unstructured Data in XML
– CLOB storage XML part in Object Relational XML
– Secondary index on XMLIndex
• Can only index XML data TEXT nodes
• Result Set Interface (new in 11.2.0.2)
– Specify Query request and hit list requirements in
XML
SQL> CREATE INDEX oracle_text_index
ON xml_data_table
(OBJECT_VALUE) INDEXTYPE IS CTXSYS.CONTEXT;

21. Index Methods (11.1)
Unstructured
XMLIndex
paragraph
book
title author author
whitepaper
title author id
content
bookstore
chapter
content
Function
based Index
(XPath)
Secondary Oracle
Text Index
BTBTre
e I
BTre
e
Index

22. Simple: Unstructured XMLIndex
SQL> CREATE INDEX xmlindex_idx
ON “XMLTYPE_COLUMN"(xdata)
INDEXTYPE IS XDB.XMLINDEX;
Index created.
SQL> CREATE INDEX xmlindex_idx
ON “XMLTYPE_TABLE"(object_value)
INDEXTYPE IS XDB.XMLINDEX;
Index created.

23. • XML Document contains:
– Semi Structured Data and Structured Data
– Supports searching and fragment extraction
– When XPath queried is not known beforehand
• XMLType CLOB or Binary XML content
• If you use an XMLIndex and/or combine it
with Structured XMLIndex(es)
Usage: Unstructured XMLIndex

24. Path Table
Path Table
Unstructured
XMLIndex
f (x)

25. Unstructured XMLIndex (UXI)
 One Path Table
 Use Path Subsetting
 Full Blown XMLIndex can be BIG
 Token Tables (XDB.X$......)
 Query re-write on Tokens
 Fuzzy Searches, //
 Optimizer Statistics
 Can be maintained Manually
 Recorded in Pending Table
 Secondary indexes possible
Path Table
Unstructured
XMLIndex
f (x)

26. Creating Unstructured XMLIndex
CREATE INDEX XMLIDX
ON XMLBINARY_TAB (object_value)
INDEXTYPE IS XDB.XMLIndex
PARAMETERS
('PATHS (INCLUDE (/ROOT/ID /ROOT/INFO/INFO_ID )
NAMESPACE MAPPING
(xmlns="http://localhost/xmlschema_bin.xsd") )
PATH TABLE path_table (TABLESPACE XML_DATA)
PATH ID INDEX pathid_idx (TABLESPACE XML_INDX)
ORDER KEY INDEX orderkey_idx (TABLESPACE XML_INDX)
VALUE INDEX value_idx (TABLESPACE XML_INDX)
ASYNC (SYNC ALWAYS) STALE (FALSE) ')
PARALLEL LOGGING;

27. Index Methods (11.2)
Structured
XMLIndex
Unstructured
XMLIndex
paragraph
book
title author author
whitepaper
title author id
content
bookstore
chapter
content
Function
based Index
(XPath)
Secondary Oracle
Text Index
Highly Structured
Islands of Data
BTBTre
e I
BTre
e
Index

28. Simple: Structured XMLIndex
• “XMLTABLE” Driven Syntax
SQL> CREATE INDEX xmlindex_sxi
on xmldata_table (doc)
indextype is xdb.xmlindex
parameters
('GROUP elementinfo_group
XMLTABLE xml_cnt_tab_elementinfo
' '/root/element' '
COLUMNS
infocol VARCHAR2(4000) PATH ' 'info' '
');
Be aware
' '

29. • With highly Structured Data
• Likely candidates: ComplexTypes
• Structured Islands of Data
– Can be nested, but only one level
– XMLTABLE “virtual” nested column hint
• Multiple “content tables”
– Multiple XPath defined same columns with
different purpose
They deliver relational performance…!
Usage: Structured XMLIndex

30. Content Table(s)
KEY INDEX
 (KEY)
 Unique BTREE Index
 Primary Key
RID INDEX
 (RID)
 NON Unique BTREE Index
Your Columns
CONTENT TABLE(s)
RID
rowid
Key
RAW
Not
null
RID
rowid
Key
RAW
Not
null
YOUR
column
s
X
YOUR
column
s
X
RID
rowid
YOUR
column
X
Key
RAW
Not
null

31. Structured XMLIndex (SXI)
• Content Table(s)
• Based on XMLTABLE syntax
• XMLTable construct can be nested but:
“Only ONE XMLType column allowed”
 VIRTUAL column
• Can be maintained Manually
• Secondary indexes possible
• LOCAL parameter (partitioning)
Content
Tables
Structured
XMLIndex
f (x)

32. Adding Structured Indexes
SQL> ALTER INDEX xmlindex_sxi
parameters
('ADD_GROUP
GROUP my_new_group
XMLTABLE xml_content_tab_new
' '/root/extra' '
COLUMNS
extracol VARCHAR2(35) PATH ' 'new_element' ' ');

33. Mixed XMLIndex Options
Unstructured
XMLIndex
Structured
XMLIndex
Structured
XMLIndex
paragraph
book
title author author
whitepaper
title author id
content
bookstore
chapter
content
Secondary
(text) Index

34. Mixed XMLIndex structures
CREATE INDEX xmlindex on TEST_RANGE_XML (doc)
indextype is xdb.xmlindex
PARAMETERS
(' PATH TABLE path_table PATHS (EXCLUDE(/root/ElementInfo)) ');
BEGIN
DBMS_XMLINDEX.registerParameter
('StructuredXML',
'ADD_GROUP GROUP ElementInfo
XMLTABLE xml_cnttable_valueinfo ' '/root/ElementInfo' '
COLUMNS ValueInfo VARCHAR2(100) PATH ' 'ValueInfo' ');
END; /
ALTER INDEX xmlindex PARAMETERS('PARAM StructuredXML');

35. XMLIndex Maintenance
• ALTER INDEX
• XMLIndex Parameter Changes
– DBMS_XMLINDEX.DROPPARAMETER
– DBMS_XMLINDEX.MODIFYPARAMETER
– DBMS_XMLINDEX.REGISTERPARAMETER
• Manual Synchronizing an XMLIndex
– DBMS_XMLINDEX.SYNCINDEX
– Pending Tables

36. “There Can Be Only One…”

37. Syntax Awareness
• SYNC=ALWAYS
– Mandatory when Combined XMLIndex
• SYNC=MANUAL
– Locking
• STALE=FALSE | TRUE
– Hmmm…
• Empty XMLIndex tables
– OOPS  I got my “XMLTABLE” Syntax etc. “wrong”

38. Notes on XMLIndex (1)
• Only ONE XMLIndex is allowed in a user
schema
– Add extra XMLIndex structures (structured or
unstructured)
via ADD_GROUP syntax
– Only SYNC=ALWAYS is allowed while using mixed
XMLIndex structures or add more than one

39. Notes on XMLIndex (2)
• You need the LOCAL parameter to create local
partitioned XMLIndexes
• An XMLIndex on a HASH partitioned XMLType
column or XMLType table, is not (yet) allowed
– But you can create an Oracle Text Index on such
structures

40. Recap
• True understanding of Storage
and Index options will provide:
– Optimal performance
– Out perform XML (Java based)
• A lot of choice:
– Problems are Complex
– Also provides Solutions
• Good design beforehand is the path to success

42. References (1)
Oracle Whitepapers
– Oracle XML DB : Choosing the Best XMLType
Storage Option for Your Use Case (PDF)
– Oracle XML DB : Best Practices to Get Optimal
Performance out of XML Queries (PDF)
Blog
– http://blog.gralike.com
• (Dedicated XMLDB blog)
• Semi-Structured XMLIndex section
• Structured XMLIndex section

43. References (2)
• Oracle Open World Presentation on XML DB
– S317428: Building Really Scalable XML
Applications with Oracle XML DB and Oracle Text
• XML DB OTN / FAQ Thread
– http://forums.oracle.com/forums/forum.jspa?foru
mID=34
– http://forums.oracle.com/forums/thread.jspa?thr
eadID=410714