xquery with user-defined functions
DESCRIPTION
XQuery with User-defined Functions. David Bedn árek [email protected] ulita.ms.mff.cuni.cz/~bednarek Department of Software Engineering Faculty of Mathematics and Physics Charles University Prague. XQuery program with user-defined functions. declare function local:toc($P) { - PowerPoint PPT PresentationTRANSCRIPT
XQuery with User-defined Functions
David Bednárek
[email protected]/~bednarek
Department of Software EngineeringFaculty of Mathematics and Physics
Charles University Prague
XQuery program with user-defined functions
declare function local:toc($P) { for $X in $P/section return <section> { $X/@* , $X/title , local:toc($X) } </section>};
<toc> { for $S in $I/book return local:toc($S)} </toc>
XQuery with user-defined functions
Turing-complete language Identification of patterns of "strong" computation
Relational algebra representation Identifier handling
Bulk-evaluation R-programs
Temporary structures Static analysis
Generation of the output document Reversed evaluation
Turing-completeness of XQuery
Identification of patterns of "strong" computation
The simplest XQuery application
XML document tree
1 23
4
A
B
C
D
XQuery evaluation tree
The simplest XQuery application
Cartesian product
1 23
4
A
B
C
D
The simplest XQuery application
Two-dimensional attribute grammar Dependence analysis
The simplest XQuery application
Turing-strong patterns Mesh Tape
Relational algebra representation
Identifier handling
Example – input document and its Dewey encoding
section
9
8
book
sectiontitle title
7 4
title
7
section
5
@id
6
/
1
p
8
p
9
section
((1)(1.9))
(3(1.5.8))
toc
sectiontitle title
(2(1.5.7)) (2(1.9.4))
title
(2(1.5.8.9))
section
((1)(1.5))
@id
(1(1.5.8.6))
/
()
/1 book1.5 section1.5.7 title1.5.8 section1.5.8.6 @id1.5.8.7 title1.5.8.9 p1.9 section1.9.4 title1.9.8 p
XQuery program and its effect on encoded documents
/1 book1.5 section1.5.7 title1.5.8 section1.5.8.6 @id1.5.8.7 title1.5.8.9 p1.9 section1.9.4 title1.9.8 p
/
() toc
()((1)(1.5)) section
()((1)(1.5))(2(1.5.7)) title
()((1)(1.5))(3(1.5.8)) section
()((1)(1.5))(2(1.5.7))(1(1.5.8.6)) @id
()((1)(1.5))(2(1.5.7))(2(1.5.8.9)) title
()((1)(1.9)) section
()((1)(1.9))(2(1.9.4)) title
declare function local:toc($P) { for $X in $P/section return <section> { $X/@* , $X/title , local:toc($X) } </section>};
<toc> { for $S in $I/book return local:toc($S)} </toc>
Example – decoded output document
section
9
8
book
sectiontitle title
7 4
title
7
section
5
@id
6
/
1
p
8
p
9
section
((1)(1.9))
(3(1.5.8))
toc
sectiontitle title
(2(1.5.7)) (2(1.9.4))
title
(2(1.5.8.9))
section
((1)(1.5))
@id
(1(1.5.8.6))
/
()
/() toc()((1)(1.5)) section()((1)(1.5)) (2(1.5.7)) title()((1)(1.5)) (3(1.5.8)) section()((1)(1.5)) (2(1.5.7))(1(1.5.8.6)) @id()((1)(1.5)) (2(1.5.7))(2(1.5.8.9)) title()((1)(1.9)) section()((1)(1.9)) (2(1.9.4)) title
Life cycle of identifiers
Bulk-evaluation
R-programs
R-programs
Handling recursion by expansion Bulk-evaluation by relational algebra
R-program
pipelinedinterpreter
expanderexpandedR-program triggers
dynamicrewriting
XMLDB
XMLDB
physicalR-program
global planselection
statistics
R-programs
DAG of relational algebra operators
Gradual expansion driven by triggers
trigger(t 1t2t2)
empty
trigger(t 1t2)
empty
m
initial(main)
final(main)
m
initial(main)
final(main)
trigger(t 1)
empty
m
initial(main)
final(main)
Temporary structures
Static analysis
Published in: "Reducing Temporary Trees in XQuery" ADBIS 2008, Pori, Finland, LNCS
Static analysis algorithm
Input: a XQuery program Output: a set of modes assigned to each sub-
expression and each variable Mode determines a particular way of
representation required Reversed evaluation is one of the modes
Time O(n2), space O(n)
Generation of the output document
Reversed evaluation
Published in: "Output-driven evaluation of XQuery" IDC 2008, Catania, Italy, Springer Verlag
Standard data flow
<section>
for $X
returnin
$P/section
toc($X)
,
$X/@*
function toc($P)
$X/title
<toc>
for $S
in
$I/book
toc($S)
$P$I
$S
$X
$P
return
main
$P
declare function local:toc($P) { for $X in $P/section return <section> { $X/@* , $X/title , local:toc($X) } </section>};
<toc> { for $S in $I/book return local:toc($S)} </toc>
Reversed data flow
<section>
for $X
returnin
$P/section
toc($X)
,
$X/@*
function toc($P)
$X/title
<toc>
for $S
in
$I/book
toc($S)
$P$I
$S
$X
$P
return
main
$P
Future work
Cost-based optimization in R-programs
Distributed/parallel XQuery engine