Difference between revisions of "XQuery Module"
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==xquery:eval== | ==xquery:eval== | ||
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{| width='100%' | {| width='100%' | ||
|- | |- | ||
| width='120' | '''Signatures''' | | width='120' | '''Signatures''' | ||
− | |{{Func|xquery:eval|$query as xs:anyAtomicType|item()*}}<br />{{Func|xquery:eval|$query as xs: | + | |{{Func|xquery:eval|$query as xs:anyAtomicType|item()*}}<br />{{Func|xquery:eval|$query as xs:anyAtomicType, $bindings as map(*)?|item()*}}<br />{{Func|xquery:eval|$query as xs:anyAtomicType, $bindings as map(*)?, $options as map(*)?|item()*}}<br /> |
|- | |- | ||
| '''Summary''' | | '''Summary''' | ||
− | |Evaluates the supplied {{Code|$query}} and returns the resulting items. If the query is of type {{Code|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 | + | |Evaluates the supplied {{Code|$query}} and returns the resulting items. If the query is of type {{Code|xs:anyURI}}, the module located at this URI will be retrieved (a relative URI will be resolved against the static base URI). Otherwise, the input is expected to be of type {{Code|xs:string}}. |
Variables and context items can be declared via {{Code|$bindings}}. The specified keys must be QNames or strings: | Variables and context items can be declared via {{Code|$bindings}}. The specified keys must be QNames or strings: | ||
* If a key is a QName, it will be directly adopted as variable name. | * If a key is a QName, it will be directly adopted as variable name. | ||
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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: | ||
+ | <syntaxhighlight lang="xquery"> | ||
+ | xquery:eval(xs:anyURI('cleanup.xq')) | ||
+ | </syntaxhighlight> | ||
* 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 /> | ||
− | < | + | <syntaxhighlight lang="xquery"> |
xquery:eval("//country", map { '': db:open('factbook') }) | xquery:eval("//country", map { '': db:open('factbook') }) | ||
− | </ | + | </syntaxhighlight> |
* 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/> | ||
− | < | + | <syntaxhighlight lang="xquery"> |
xquery:eval(".", map { '': 'XML' }), | xquery:eval(".", map { '': 'XML' }), | ||
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map { '{URI}xml': 'XML' } | map { '{URI}xml': 'XML' } | ||
) | ) | ||
− | </ | + | </syntaxhighlight> |
* 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/> | ||
− | < | + | <syntaxhighlight lang="xquery"> |
declare namespace pref = 'URI'; | declare namespace pref = 'URI'; | ||
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let $vars := map { xs:QName('pref:xml'): 'XML' } | let $vars := map { xs:QName('pref:xml'): 'XML' } | ||
return xquery:eval($query, $vars) | return xquery:eval($query, $vars) | ||
− | </ | + | </syntaxhighlight> |
|} | |} | ||
==xquery:eval-update== | ==xquery:eval-update== | ||
− | |||
− | |||
{| width='100%' | {| width='100%' | ||
|- | |- | ||
| width='120' | '''Signatures''' | | width='120' | '''Signatures''' | ||
− | |{{Func|xquery:eval-update|$query as xs: | + | |{{Func|xquery:eval-update|$query as xs:anyAtomicType|item()*}}<br />{{Func|xquery:eval-update|$query as xs:anyAtomicType, $bindings as map(*)?|item()*}}<br />{{Func|xquery:eval-update|$query as xs:anyAtomicType, $bindings as map(*)?, $options as map(*)?|item()*}}<br /> |
|- | |- | ||
| '''Summary''' | | '''Summary''' | ||
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| '''Errors''' | | '''Errors''' | ||
|{{Error|update|#Errors}} the query contains no [[XQuery Update#Updating Expressions|updating expressions]].<br/>{{Error|permission|#Errors}} insufficient permissions for evaluating the query.<br/>{{Error|timeout|#Errors}} query execution exceeded timeout.<br/>{{Error|limit|#Errors}} query execution exceeded memory limit.<br/>{{Error|nested|#Errors}} nested query evaluation is not allowed.<br/>Any other error that may occur while evaluating the query. | |{{Error|update|#Errors}} the query contains no [[XQuery Update#Updating Expressions|updating expressions]].<br/>{{Error|permission|#Errors}} insufficient permissions for evaluating the query.<br/>{{Error|timeout|#Errors}} query execution exceeded timeout.<br/>{{Error|limit|#Errors}} query execution exceeded memory limit.<br/>{{Error|nested|#Errors}} nested query evaluation is not allowed.<br/>Any other error that may occur while evaluating the query. | ||
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|- | |- | ||
− | | | + | | '''Examples''' |
− | | | + | | |
− | + | * Removes entries from a temporary databases and returns an info string: | |
− | + | <syntaxhighlight lang="xquery"> | |
− | + | xquery:eval-update(" | |
− | + | delete node db:open('tmp')/*, | |
− | + | update:output('TEMPORARY DATABASE WAS CLEANED UP') | |
− | + | ") | |
− | + | </syntaxhighlight> | |
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|} | |} | ||
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* {{Code|compile}}: additionally compiles the query after parsing it. By default, this option is {{Code|false}}. | * {{Code|compile}}: additionally compiles the query after parsing it. By default, this option is {{Code|false}}. | ||
* {{Code|plan}}: returns an XML representation of the internal query plan. By default, this option is {{Code|true}}. The naming of the expressions in the query plan may change over time | * {{Code|plan}}: returns an XML representation of the internal query plan. By default, this option is {{Code|true}}. The naming of the expressions in the query plan may change over time | ||
− | * {{Code|pass}}: | + | * {{Code|pass}}: by default, the option is {{Code|false}}. If an error is raised, the line/column number and the optional file uri will refer to the location of the function call. If the option is enabled, the line/column and file uri will be adopted from the raised error. |
* {{Code|base-uri}}: set [https://www.w3.org/TR/xquery-31/#dt-static-base-uri base-uri property] for the query. This URI will be used when resolving relative URIs by functions such as {{Code|fn:doc}}. | * {{Code|base-uri}}: set [https://www.w3.org/TR/xquery-31/#dt-static-base-uri base-uri property] for the query. This URI will be used when resolving relative URIs by functions such as {{Code|fn:doc}}. | ||
|- | |- | ||
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| | | | ||
* {{Code|xquery:parse("1 + 3")}} returns: | * {{Code|xquery:parse("1 + 3")}} returns: | ||
− | < | + | <syntaxhighlight lang="xml"> |
<MainModule updating="false"> | <MainModule updating="false"> | ||
<QueryPlan compiled="false"> | <QueryPlan compiled="false"> | ||
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</QueryPlan> | </QueryPlan> | ||
</MainModule> | </MainModule> | ||
− | </ | + | </syntaxhighlight> |
|} | |} | ||
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| | | | ||
* The following function sleeps in parallel; it will be finished in 1 second if your system has at least 2 cores: | * The following function sleeps in parallel; it will be finished in 1 second if your system has at least 2 cores: | ||
− | < | + | <syntaxhighlight 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)) | ||
− | </ | + | </syntaxhighlight> |
* In the following query, up to four URLs will be requested in parallel: | * In the following query, up to four URLs will be requested in parallel: | ||
− | < | + | <syntaxhighlight lang="xquery"> |
xquery:fork-join( | xquery:fork-join( | ||
for $segment in 1 to 4 | for $segment in 1 to 4 | ||
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return function() { http:send-request((), $url) } | return function() { http:send-request((), $url) } | ||
) | ) | ||
− | </ | + | </syntaxhighlight> |
|- | |- | ||
|'''Errors''' | |'''Errors''' | ||
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;Version 9.2 | ;Version 9.2 | ||
− | * Deleted: [[#xquery: | + | * Deleted: xquery:invoke, xquery:invoke-update (merged with [[#xquery:eval|xquery:eval]] and [[#xquery:eval-update|xquery:eval-update]]) |
;Version 9.0 | ;Version 9.0 |
Revision as of 14:24, 27 February 2020
This XQuery Module contains functions for parsing and evaluating XQuery strings at runtime, and to run code in parallel.
Contents
Conventions
All functions and errors in this module are assigned to the http://basex.org/modules/xquery
namespace, which is statically bound to the xquery
prefix.
Dynamic Evaluation
xquery:eval
Signatures | xquery:eval($query as xs:anyAtomicType) as item()* xquery:eval($query as xs:anyAtomicType, $bindings as map(*)?) as item()* xquery:eval($query as xs:anyAtomicType, $bindings as map(*)?, $options as 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 |
<syntaxhighlight lang="xquery"> xquery:eval(xs:anyURI('cleanup.xq')) </syntaxhighlight>
<syntaxhighlight lang="xquery"> xquery:eval("//country", map { : db:open('factbook') }) </syntaxhighlight>
<syntaxhighlight lang="xquery"> 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' } ) </syntaxhighlight>
<syntaxhighlight lang="xquery"> 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, $vars) </syntaxhighlight> |
xquery:eval-update
Signatures | xquery:eval-update($query as xs:anyAtomicType) as item()* xquery:eval-update($query as xs:anyAtomicType, $bindings as map(*)?) as item()* xquery:eval-update($query as xs:anyAtomicType, $bindings as map(*)?, $options as map(*)?) as item()* |
Summary | Evaluates a query as updating expression. All updates will be added to the Pending Update List of the main query and performed after the evaluation of the main query. The rules for all arguments are the same as for xquery:eval. |
Errors | update : the query contains no updating expressions.permission : insufficient permissions for evaluating the query.timeout : query execution exceeded timeout.limit : query execution exceeded memory limit.nested : nested query evaluation is not allowed.Any other error that may occur while evaluating the query. |
Examples |
<syntaxhighlight lang="xquery"> xquery:eval-update(" delete node db:open('tmp')/*, update:output('TEMPORARY DATABASE WAS CLEANED UP') ") </syntaxhighlight> |
XQuery Parsing
xquery:parse
Signatures | xquery:parse($query as xs:string) as item()? xquery:parse($query as xs:string, $options as map(*)?) as item()? |
Summary | Parses the specified $query string as XQuery module and returns the resulting query plan. The $options parameter influences the output:
|
Errors | Any error that may occur while parsing the query. |
Examples |
<syntaxhighlight lang="xml"> <MainModule updating="false"> <QueryPlan compiled="false"> <Arith op="+"> <Int value="1" type="xs:integer"/> <Int value="3" type="xs:integer"/> </Arith> </QueryPlan> </MainModule> </syntaxhighlight> |
xquery:parse-uri
Signatures | xquery:parse-uri($uri as xs:string) as item()? xquery:parse-uri($uri as xs:string, $options as map(*)?) as item()? |
Summary | Parses the XQuery module located at $uri and returns the resulting query plan. A relative URI will be resolved against the static base URI of the query. The rules for the $options parameter are the same as for xquery:parse.
|
Errors | Any error that may occur while parsing the query. |
Parallelized Execution
Parallel query execution is recommendable if you have various calls that require a lot of time, but that cannot be sped up by rewriting the code. This is e. g. the case if external URLs are called. If you are parallelizing local data reads (such as the access to a database), single-threaded queries will usually be faster, because parallelized access to disk data often results in randomized access patterns, which will rarely be optimized by the caching strategies of HDDs, SSDs, or the operating system.
xquery:fork-join
Signatures | xquery:fork-join($functions as function(*)*) as item()*
|
Summary | This function executes the supplied (non-updating) functions in parallel. |
Examples |
<syntaxhighlight lang="xquery"> let $f := function() { prof:sleep(1000) } return xquery:fork-join(($f, $f)) </syntaxhighlight>
<syntaxhighlight lang="xquery"> xquery:fork-join( for $segment in 1 to 4 let $url := 'http://url.com/path/' || $segment return function() { http:send-request((), $url) } ) </syntaxhighlight> |
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 9.2
- Deleted: xquery:invoke, xquery:invoke-update (merged with xquery:eval and xquery: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.