Difference between revisions of "XQuery Module"
m (Text replacement - "</syntaxhighlight>" to "</pre>") |
m (Text replacement - "<syntaxhighlight lang="xquery">" to "<pre lang='xquery'>") |
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* {{Code|xquery:eval("1+3")}} returns {{Code|4}}.<br/> | * {{Code|xquery:eval("1+3")}} returns {{Code|4}}.<br/> | ||
* If a URI is supplied, the query in the specified file will be evaluated: | * If a URI is supplied, the query in the specified file will be evaluated: | ||
− | < | + | <pre lang='xquery'> |
xquery:eval(xs:anyURI('cleanup.xq')) | xquery:eval(xs:anyURI('cleanup.xq')) | ||
</pre> | </pre> | ||
* You can bind the context and e.g. operate on a certain database only:<br/> | * You can bind the context and e.g. operate on a certain database only:<br/> | ||
− | < | + | <pre lang='xquery'> |
xquery:eval("//country", map { '': db:get('factbook') }) | xquery:eval("//country", map { '': db:get('factbook') }) | ||
</pre> | </pre> | ||
* The following expressions use strings as keys. All of them return 'XML':<br/> | * The following expressions use strings as keys. All of them return 'XML':<br/> | ||
− | < | + | <pre lang='xquery'> |
xquery:eval(".", map { '': 'XML' }), | xquery:eval(".", map { '': 'XML' }), | ||
Line 61: | Line 61: | ||
</pre> | </pre> | ||
* The following expressions use QNames as keys. All of them return 'XML':<br/> | * The following expressions use QNames as keys. All of them return 'XML':<br/> | ||
− | < | + | <pre lang='xquery'> |
declare namespace pref = 'URI'; | declare namespace pref = 'URI'; | ||
Line 94: | Line 94: | ||
| | | | ||
* Removes entries from a temporary databases and returns an info string: | * Removes entries from a temporary databases and returns an info string: | ||
− | < | + | <pre lang='xquery'> |
xquery:eval-update(" | xquery:eval-update(" | ||
delete node db:get('tmp')/*, | delete node db:get('tmp')/*, | ||
Line 164: | Line 164: | ||
| | | | ||
* Request 100 URLs, use at most 8 parallel threads: | * Request 100 URLs, use at most 8 parallel threads: | ||
− | < | + | <pre lang='xquery'> |
xquery:fork-join( | xquery:fork-join( | ||
for $segment in 1 to 100 | for $segment in 1 to 100 | ||
Line 173: | Line 173: | ||
</pre> | </pre> | ||
* Parallel sleep function calls. The function is expected to finish in 1 second if the system has at least 2 cores: | * Parallel sleep function calls. The function is expected to finish in 1 second if the system has at least 2 cores: | ||
− | < | + | <pre lang='xquery'> |
let $f := function() { prof:sleep(1000) } | let $f := function() { prof:sleep(1000) } | ||
return xquery:fork-join(($f, $f)) | return xquery:fork-join(($f, $f)) |
Revision as of 18:33, 1 December 2023
This XQuery Module contains functions for parsing and evaluating XQuery strings at runtime, and to run code in parallel.
Contents
Conventions
All functions and errors in this module are assigned to the http://basex.org/modules/xquery
namespace, which is statically bound to the xquery
prefix.
Evaluation
xquery:eval
Updated with Version 11: The Clark notation was replaced with the Expanded QNames notation.
Signature | xquery:eval( $query as xs:anyAtomicType, $bindings as map(*)? := map { }, $options as map(*)? := map { } ) as item()* |
Summary | Evaluates the supplied $query and returns the resulting items. If the query is of type xs:anyURI , the module located at this URI will be retrieved (a relative URI will be resolved against the static base URI). Otherwise, the input is expected to be of type xs:string .
Variables and context items can be declared via
The
|
Errors | update : the query contains updating expressions.permission : insufficient permissions for evaluating the query.timeout : query execution exceeded timeout.limit : query execution exceeded memory limit.nested : nested query evaluation is not allowed.Any other error that may occur while evaluating the query. |
Examples |
xquery:eval(xs:anyURI('cleanup.xq'))
xquery:eval("//country", map { '': db:get('factbook') })
xquery:eval(".", map { '': 'XML' }),
xquery:eval("declare variable $xml external; $xml", map { 'xml': 'XML' }),
xquery:eval(
"declare namespace pref='URI';
declare variable $pref:xml external;
$pref:xml",
map { '{URI}xml': 'XML' }
)
declare namespace pref = 'URI';
xquery:eval("declare variable $xml external; $xml", map { xs:QName('xml'): 'XML' }),
let $query := "declare namespace pref='URI';
declare variable $pref:xml external;
$pref:xml"
let $vars := map { xs:QName('pref:xml'): 'XML' }
return xquery:eval($query, $vars)
|
xquery:eval-update
Signature | xquery:eval-update( $query as xs:anyAtomicType, $bindings as map(*)? := (), $options as map(*)? := () ) as item()* |
Summary | Evaluates a query as updating expression. All updates will be added to the Pending Update List of the main query and performed after the evaluation of the main query. The rules for all arguments are the same as for xquery:eval .
|
Errors | update : the query contains no updating expressions.permission : insufficient permissions for evaluating the query.timeout : query execution exceeded timeout.limit : query execution exceeded memory limit.nested : nested query evaluation is not allowed.Any other error that may occur while evaluating the query. |
Examples |
xquery:eval-update("
delete node db:get('tmp')/*,
update:output('TEMPORARY DATABASE WAS CLEANED UP')
")
|
Parsing
xquery:parse
Signature | xquery:parse( $query as xs:anyAtomicType, $options as map(*)? := map { } ) as item()? |
Summary | Parses the specified $query as XQuery module and returns the resulting query plan. If the query is of type xs:anyURI , the module located at this URI will be retrieved (a relative URI will be resolved against the static base URI). Otherwise, the input is expected to be of type xs:string . The $options parameter influences the output:
|
Errors | Any error that may occur while parsing the query. |
Examples |
<syntaxhighlight lang="xml"> <MainModule updating="false"> <QueryPlan compiled="false"> <Arith op="+"> <Int value="1" type="xs:integer"/> <Int value="3" type="xs:integer"/> </Arith> </QueryPlan> </MainModule> |
Parallelized Execution
Parallel query execution is recommendable if you have various calls that require a lot of time, but that cannot be sped up by rewriting the code. This is e. g. the case if external URLs are called. If you are parallelizing local data reads (such as the access to a database), single-threaded queries will usually be faster, because parallelized access to disk data often results in randomized access patterns, which will rarely be optimized by the caching strategies of HDDs, SSDs, or the operating system.
xquery:fork-join
Updated with Version 11: Options added.
Signature | xquery:fork-join( $functions as function(*)*, $options as map(*)? := map { } ) as item()* |
Summary | This function executes the supplied (non-updating) $functions in parallel. The following $options are available:
|
Examples |
xquery:fork-join(
for $segment in 1 to 100
let $url := 'http://url.com/path/' || $segment
return function() { http:send-request((), $url) },
map { 'parallel': 8 }
)
let $f := function() { prof:sleep(1000) }
return xquery:fork-join(($f, $f))
|
Errors | error : an unexpected error occurred.
|
Errors
Code | Description |
---|---|
permission
|
Insufficient permissions for evaluating the query. |
update
|
updating expression found or expected. |
timeout
|
Query execution exceeded timeout. |
memory
|
Query execution exceeded memory limit. |
nested
|
Nested query evaluation is not allowed. |
error
|
An unexpected error occurred. |
Changelog
- Version 11
- Updated:
xquery:fork-join
: Options added. - Updated: The Clark notation was replaced with the Expanded QNames notation.
- Version 10
- Deleted: xquery:parse-uri (merged with
xquery:parse
) - Updated:
xquery:parse
: Template:$query can additionally be of typexs:anyURI
.
- Version 9.2
- Deleted: xquery:invoke, xquery:invoke-update (merged with
xquery:eval
andxquery:eval-update
)
- Version 9.0
- Added:
xquery:invoke-update
- Updated:
xquery:eval
:pass
option added - Updated:
xquery:parse
,xquery:parse-uri
:base-uri
option added - Updated: xquery:update renamed to
xquery:eval-update
- Updated: error codes updated; errors now use the module namespace
- Version 8.5
- Added:
xquery:fork-join
- Updated:
xquery:eval
:base-uri
option added - Updated: Relative URIs will always be resolved against the static base URI of the query
- Deleted: xquery:type (moved to Profiling Module)
- Version 8.4
- Added:
xquery:parse-uri
- Updated:
xquery:parse
:pass
option added
- Version 8.0
- Added: xquery:update,
xquery:parse
- Deleted: xquery:evaluate (opened databases will now be closed by main query)
- Version 7.8.2
- Added:
$options
argument
- Version 7.8
- Added:
xquery:evaluate
- Updated: used variables must be explicitly declared in the query string.
This module was introduced with Version 7.3. Functions have been adopted from the obsolete Utility Module.