Download VLDB 2003 XML Schemas in Oracle XML DB Presentation

Efficient XSLT Processing in
Relational Database System
Zhen Hua Liu
Anguel Novoselsky
Oracle Corporation
VLDB 2006
Agenda
 XML Processing Languages Overview
 XSLT Processing - Coprocessor Vs
Integrated Approach
 XSLT to XQuery Rewrite Translation
Technique
 Performance Evaluation
 Conclusion
 Q&A
XML Processing Languages
 XQuery/XPath XSLT
 SQL/XML –integration XML and XQuery/XPath into
SQL (http://www.sqlx.org)
 SQL/XML (Oracle XMLDB) –
 XMLTransform – Oracle XMLDB extension
operator: embedding XSLT in SQL
 SELECT XMLTransform(emp.resume,
‘XSLT code’)
FROM emp;
// resume is of XMLType column of table emp
XQuery, XSLT, SQL/XML
Comparison
 All are Declarative Languages ! (Central Dogma in
declarative query processing)
 Share common XQuery Data Model
 SQL/XML XMLType is based on XQuery Data Model
 XQuery & SQL/XML
 More database centric
 Share the same paradigm – Selection, Projection (XML
Construction), Join, Order
 XSLT
 Database Foreign - Template Rule Matching based Execution
Model
 XLST is more declarative than XQuery
 Impedance Mismatch with XQuery/SQL Processing Model,
how to run XSLT in RDBMS ?
Multi-Coprocessors Approach
 Embed off-the-shelf Xquery/XSLT processors into a SQL engine
XSLT(Transform)
XSLT Engine
XQuery(XMLQue
ry)
SQL Engine
XQuery Data
Model
Instances
Input
XQuery DM
instances output
XQuery Engine
Issues & Challenges with
Coprocessor Approach
 Fully composable in SQL/XML: Can we optimize
XSLT, XQuery, XPath as one language ? Cross
Language Optimization Feasible ?
 XML is stored & Indexed: Can XSLT processing
leverage index on XML in RDBMS?
 How to make XSLT template rule matching
based execution model “fit” into RDBMS
processing Model ?
XQuery/XSLT/SQL/XML
Integrated Architecture
XSLT to XQuery Rewrite
SQL/XML
XQuery
XSLT
Common algebraic operator tree – storage
independent optimization
XMLType Abstraction
XML Storage/Index dependent Optimization
OR Storage
Binary XML/ XMLIndex
SQLX View/Relational Data
Extended/Hybrid Model
XSLT to XQuery Rewrite
Translation
General XSLT to XQuery
Translate Technique
 Fokoue etc “Compiling XSLT 2.0 into XQuery 1.0” paper at
WWW 2005
 Translate XSLT template into XQuery Function
 Translate XSLT instruction into corresponding XQuery
construct
 Translate <xsl:apply-template> into XQuery function calls
with large XQuery conditional expression matching XSLT
pattern
 Issues
 Resultant XQuery is cumbersome and requires aggressive
optimization
 Where to Add Intelligence in the translation ?
XSLT to XQuery Rewrite
example
 XMLType view over relational data
CREATE VIEW dept_emp
AS
SELECT
XMLElement("dept",
XMLElement("dname", dname),
XMLElement("loc", loc),
XMLElement("employees",
(SELECT XMLAgg(XMLElement("emp",
XMLElement("empno", empno),
XMLElement("ename", ename),
XMLElement("sal", sal)))
FROM emp
WHERE emp.deptno = dept.deptno))) as dept_content
FROM dept
Example contd..
 Result of XMLType View
============================================================
<dept>
dname>ACCOUNTING</dname>
<loc>NEW YORK</loc>
<employees>
<emp>
<empno>7782</empno>
<ename>CLARK</ename>
<sal>2450</sal>
</emp>
<emp>
<empno>7934</empno>
<ename>MILLER</ename>
<sal>1300</sal>
</emp>
</employees>
</dept>
Example- XSLT on XMLType -1
SELECT XMLTransform(dept_emp.dept_content,
'<?xml version="1.0"?><xsl:stylesheet version="1.0“
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
>
<xsl:template match="dept">
<H1>HIGHLY PAID DEPT EMPLOYEES</H1>
<xsl:apply-templates/>
</xsl:template>
<xsl:template match="dname">
<H2>Department name: <xsl:value-of
select="."/></H2>
</xsl:template>
<xsl:template match="loc">
<H2>Department location: <xsl:value-of
select="."/></H2>
</xsl:template>
Example- XSLT on XMLType -2
<xsl:template match="employees">
<H2>Employees Table</H2>
<table border="2">
<td><b>EmpNo</b></td>
<td><b>Name</b></td>
<td><b>Weekly Salary</b></td>
<xsl:apply-templates select="emp[sal > 2000]"/>
</table>
</xsl:template>
<xsl:template match = "emp">
<tr>
<td><xsl:value-of select="empno"/></td>
<td><xsl:value-of select="ename"/></td>
<td><xsl:value-of select="sal"/></td>
</tr>
</xsl:template>
Example- XSLT on XMLType -3
<xsl:template match="text()">
<xsl:value-of select="."/>
</xsl:template> </xsl:stylesheet>')
FROM dept_emp;
Input XML Structural Info with
XSLT template Analysis
roo
t
dept template
dept
default template
dnam
e
employees
loc
dname template
loc template
emp
text
text
Employees template
emp template
text
Text template
XSLT Template Invocation
Graph
root
Default template
dept
dept template
dname
dname template
text
Text template
loc
loc template
employees
Employees template
text
Text template
Emp[sal>2000]
emp template
text
Text template
Example- XQuery from XSLT
SELECT XMLQuery(
'declare variable $var000 := .;
(: builtin template :)
(
let $var002 := $var000/dept
return
(: <xsl:template match="dept"> :)
(
<H1>HIGHLY PAID DEPT EMPLOYEES</H1>,
(
let $var003 := $var002/dname
return
(: <xsl:template match="dname"> :)
<H2>{fn:concat("Department name: ", fn:string($var003))}</H2>,
let $var003 := $var002/loc
return
(: <xsl:template match="loc"> :)
<H2>{fn:concat("Department location: ",fn:string($var003))}</H2>,
Example- XQuery from XSLT
let $var003 := $var002/employees
return
(: <xsl:template match="employees"> :)
(
<H2>Employees Table</H2>,
<table border="2">
{
<td><b>EmpNo</b></td>,
<td><b>Name</b></td>,
<td><b>Weekly Salary</b></td>,
(
Example- XQuery from XSLT
Rewrite
for $var005 in ($var003/emp[sal > 2000])
return
(: <xsl:template match="emp"> :)
<tr>
<td>{fn:string($var005/empno)}</td>
<td>{fn:string($var005/ename)}</td>
<td>{fn:string($var005/sal)}</td>
</tr>
)
}
</table>
)
)
)
)' PASSING dept_emp.dept_content RETURNING CONTENT) FROM DEPT
FROM dept_emp
Final Optimized SQL/XML Query

SELECT XMLConcat(
XMLElement( "H1",'HIGHLY PAID DEPT EMPLOYEES'),
XMLElement( "H2",'Department name: ' ||"SYS_ALIAS_4"."DNAME"),
XMLELement( "H2",'Department location:’ ||"SYS_ALIAS_4"."LOC"),
XMLELement( "H2",'Employees Table'),
XMLElement( "table",XMLAttributes('2' AS "border"),
XMLElement( "td",
XMLElement( "b",'EmpNo')),
XMLElement( "td",XMLElement( "b",'Name')),
XMLElement( "td",XMLElement( "b",'Weekly Salary')),
(SELECT XMLAGG(
XMLElement( "tr",
XMLElement( "td","EMP"."EMPNO"),
XMLElement( "td","EMP"."ENAME"),
XMLElement( "td","EMP"."SAL")))
FROM EMP
WHERE SAL > 2000
AND DEPTNO=DEPT.DEPTNO)))
FROM DEPT
XSLT to XQuery Rewrite Key
 Leverge XML structural information to
generate Template Invocation Graph
 XML Schema, DTD, SQL/XML construction
functions
 Inline Template with caller
 This generates compact XQuery
amendable for further optimization
 Cancellation with XML view / relational data
 Path/Value Index for binary XML
Partial Evaluation
 Partial Evaluation to obtain template invocation graph
 Application computation is described as F(X,Y), X
changes less frequently than Y and significant part of F’s
computation depends on X.
 Optimize F statically by holding X as constant
 Key observation – let F be the XSLT stylesheet, X be the
input XML structural information, Y be the actual XML
instance document content
Comparison with Related Work
 Fokoue - “Compiling XSLT 2.0 into XQuery 1.0”
WWW 2005
 Not leveraging Input XML Structure Information for
optimizing XQuery generation process
 Concluded context sensitive flow analysis & function
specialization for static optimization
 Our work –
 Optimization of XSLT based on input XML structure
 Leverage Partial Evaluation for obtaining template
invocation graph
Comparison with Related Work
 Moerkotte - “Incorporating XSL Processing Into
Database Engines” VLDB 2002
 XSLT into internal algebra and integrate with
RDBMS
 Concluded future research in combined
optimizations of XSLT with XML construction
 Our work:
 XSLT into XQuery
 Combined optimizations of XSLT with XML input
Comparison with Related Work
 Jain & Li etc - “Translating XSLT Programs to
Efficient SQL Queries” WWW 2002 &
“Composing XSL Transformations with XML
Publishing Views” SIGMOD 2003
 Our work:
 XQuery as intermediate language
 Work with any XML storage/Index Model
Performance Evaluation
XSLT Mark
 Db-one row query – Index Probe (Table Scan Vs
Index Scan)
Rewrite – Integrated Approach
No-Rewrite – Coprocessor Approach
7000
6000
5000
4000
Rewrite
3000
No-Rewrite
2000
1000
0
8M
16M
32M
64M
XSLT Mark
 Avts, metric: XML construction
 Chart, total: XSLT uses xquery aggregate
functions: count/sum
1200
1000
800
600
No-Rewrite
400
Rewrite
200
0
avts
case
chart
case
metric
case
total
case
Conclusions
 Efficient XSLT processing in RDBMS is feasible
despite the template rule based XSLT language
 Use XQuery as intermediate language to which
XSLT is translated
 Leverage XML input structural information to get
efficient & compact XQuery
 Index Probing, pull based execution model,
parallel aggregation, sort applicable to XSLT in
RDMS engine
 XSLT is native to RDBMS, just as
XQuery,SQL/XML
Questions