updated version

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

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

6. Refinement

7. Structured or Semi-Structured or…
Structured
Semi
Structured

8. Unstructured Content

9. Document Driven / Data Driven

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

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

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

19. Storage Models (xmltype)
• CLOB
– Default until 11.2.0.2.0 (deprecated in 12.1)
– Non-Schema Based
• Binary XML
– Oracle 11 and Onwards
– Schema and Non-Schema Based
• Object Relational (+Hybrid)
– Nested Tables, Types, Varray’s
– Schema Based

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

21. Index Methods (xmltype)

22. 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

23. Index Methods (10.x)
BTre
BTre
BT
e
eI
Index
bookstore
Function
based Index
(XPath)
book whitepaper
title author author chapter title author id paragraph
content content
Oracle Text Index

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

25. 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");

26. Index Alternatives
SQL> CREATE INDEX function_based_again_idx
ON xml_data_table
(CAST("XMLDATA". "TEXTID“ as VARCHAR2(10)));
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)));

27. 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 (<12.1!)
• 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;

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

29. Usage: Unstructured XMLIndex
• 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)

30. 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.

31. 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;

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

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

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

35. Usage: Structured XMLIndex
• With highly Structured Data
• Likely candidates: ComplexTypes
• Structured Islands of Data
– Can be nested, but officially only one level
– XMLTABLE “virtual” nested column hint
• Will create (multiple) “Content Tables”
– Multiple XPath defined same columns with
different purpose
They deliver relational performance…!

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

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

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

39. 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' ' ');

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

41. 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');

42. 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

43. “There Can Be Only One…”

44. 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”

45. Notes on XMLIndex (1)
• Only ONE XMLIndex is allowed per column of
XMLType table
– Add extra XMLIndex structures (structured or
unstructured)
via ADD_GROUP syntax
– Only SYNC=ALWAYS is allowed while using mixed
XML Index structures or add more than one (11g)

46. Notes on XMLIndex (2)
• You need the LOCAL parameter to create local
partitioned XML Indexes
• An XMLIndex on a HASH partitioned XMLType
column or XMLType table, is not allowed (11g)
– But you can create an Oracle Text Index on such
structures

47. 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

49. 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
– www.xmldb.nl
• (Dedicated XMLDB blog)
• Semi-Structured XMLIndex section
• Structured XMLIndex section

50. 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