Difference between revisions of "XQuery Module"

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All functions and errors in this module are assigned to the <code><nowiki>http://basex.org/modules/xquery</nowiki></code> namespace, which is statically bound to the {{Code|xquery}} prefix.<br/>
 
All functions and errors in this module are assigned to the <code><nowiki>http://basex.org/modules/xquery</nowiki></code> namespace, which is statically bound to the {{Code|xquery}} prefix.<br/>
  
=Dynamic Evaluation=
+
=Evaluation=
  
 
==xquery:eval==
 
==xquery:eval==
  
{{Mark|Updated with 9.2}}: First argument can be a URI (xquery:invoke was removed).
+
{{Announce|Updated with Version 11}}: The Clark notation was replaced with the [[XQuery 3.0#Expanded QNames|Expanded QNames]] notation.
  
 
{| width='100%'
 
{| width='100%'
|-
+
|- valign="top"
| width='120' | '''Signatures'''
+
| width='120' | '''Signature'''
|{{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 />
+
|<pre>xquery:eval(
|-
+
  $query     as xs:anyAtomicType,
 +
  $bindings as map(*)?           := map { },
 +
  $options  as map(*)?           := map { }
 +
) as item()*</pre>
 +
|- valign="top"
 
| '''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 is expected to be of type {{Code|xs:string}}.
 
|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.
* It a key is a string, it may be prefixed with a dollar sign. Namespace can be specified using the [http://www.jclark.com/xml/xmlns.htm Clark Notation].
+
* It a key is a string, it may be prefixed with a dollar sign. Namespace can be specified using the [[XQuery 3.0#Expanded QNames|Expanded QNames]] notation.
 
* If the specified string is empty, the value will be bound to the context item.
 
* If the specified string is empty, the value will be bound to the context item.
 
The {{Code|$options}} parameter contains evaluation options:
 
The {{Code|$options}} parameter contains evaluation options:
Line 28: Line 32:
 
* {{Code|base-uri}}: set [https://www.w3.org/TR/xquery-31/#dt-static-base-uri base-uri property] for the query. Overwrites the base URI of the query; 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. Overwrites the base URI of the query; will be used when resolving relative URIs by functions such as {{Code|fn:doc}}.
 
* {{Code|pass}}: passes on the original error info (line and column number, optional file uri). By default, this option is {{Code|false}}.
 
* {{Code|pass}}: passes on the original error info (line and column number, optional file uri). By default, this option is {{Code|false}}.
|-
+
|- valign="top"
 
| '''Errors'''
 
| '''Errors'''
 
|{{Error|update|#Errors}} the query contains [[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 [[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.
|-
+
|- valign="top"
 
| '''Examples'''
 
| '''Examples'''
 
|
 
|
* {{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 class='brush:xquery'>
+
<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 class='brush:xquery'>
+
<pre lang='xquery'>
xquery:eval("//country", map { '': db:open('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 class='brush:xquery'>
+
<pre lang='xquery'>
 
xquery:eval(".", map { '': 'XML' }),
 
xquery:eval(".", map { '': 'XML' }),
  
Line 57: 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 class='brush:xquery'>
+
<pre lang='xquery'>
 
declare namespace pref = 'URI';
 
declare namespace pref = 'URI';
  
Line 71: Line 75:
  
 
==xquery:eval-update==
 
==xquery:eval-update==
 
{{Mark|Updated with 9.2}}: First argument may be a URI (xquery:invoke-update was removed).
 
  
 
{| width='100%'
 
{| width='100%'
|-
+
|- valign="top"
| width='120' | '''Signatures'''
+
| width='120' | '''Signature'''
|{{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 />
+
|<pre>xquery:eval-update(
|-
+
  $query     as xs:anyAtomicType,
 +
  $bindings as map(*)?           := (),
 +
  $options  as map(*)?           := ()
 +
) as item()*</pre>
 +
|- valign="top"
 
| '''Summary'''
 
| '''Summary'''
|Evaluates a query as updating expression. All updates will be added to the [[XQuery Update#Pending Update List|Pending Update List]] of the main query and performed after the evaluation of the main query.<br />The rules for all arguments are the same as for [[#xquery:eval|xquery:eval]].
+
|Evaluates a query as updating expression. All updates will be added to the [[XQuery Update#Pending Update List|Pending Update List]] of the main query and performed after the evaluation of the main query.<br/>The rules for all arguments are the same as for {{Function||xquery:eval}}.
|-
+
|- valign="top"
 
| '''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.
|-
+
|- valign="top"
 
| '''Examples'''
 
| '''Examples'''
 
|
 
|
 
* Removes entries from a temporary databases and returns an info string:
 
* Removes entries from a temporary databases and returns an info string:
<pre class="brush:xquery">
+
<pre lang='xquery'>
 
xquery:eval-update("
 
xquery:eval-update("
   delete node db:open('tmp')/*,
+
   delete node db:get('tmp')/*,
 
   update:output('TEMPORARY DATABASE WAS CLEANED UP')
 
   update:output('TEMPORARY DATABASE WAS CLEANED UP')
 
")
 
")
Line 96: Line 102:
 
|}
 
|}
  
=XQuery Parsing=
+
=Parsing=
  
 
==xquery:parse==
 
==xquery:parse==
  
 
{| width='100%'
 
{| width='100%'
|-
+
|- valign="top"
| width='120' | '''Signatures'''
+
| width='120' | '''Signature'''
|{{Func|xquery:parse|$query as xs:string|item()?}}<br />{{Func|xquery:parse|$query as xs:string, $options as map(*)?|item()?}}<br />
+
|<pre>xquery:parse(
|-
+
  $query   as xs:anyAtomicType,
 +
  $options as map(*)?           := map { }
 +
) as item()?</pre>
 +
|- valign="top"
 
| '''Summary'''
 
| '''Summary'''
|Parses the specified {{Code|$query}} string as XQuery module and returns the resulting query plan. The {{Code|$options}} parameter influences the output:
+
|Parses the specified {{Code|$query}} as XQuery module and returns the resulting query plan. If the query is of type {{Code|xs:anyURI}}, the module located at this URI will be retrieved (a relative URI will be resolved against the static base URI). Otherwise, the input is expected to be of type {{Code|xs:string}}. The {{Code|$options}} parameter influences the output:
 
* {{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}}: 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|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}}.
|-
+
|- valign="top"
 
| '''Errors'''
 
| '''Errors'''
 
|Any error that may occur while parsing the query.
 
|Any error that may occur while parsing the query.
|-
+
|- valign="top"
 
| '''Examples'''
 
| '''Examples'''
 
|
 
|
 
* {{Code|xquery:parse("1 + 3")}} returns:
 
* {{Code|xquery:parse("1 + 3")}} returns:
<pre class='brush:xml'>
+
<pre lang="xml">
 
<MainModule updating="false">
 
<MainModule updating="false">
 
   <QueryPlan compiled="false">
 
   <QueryPlan compiled="false">
Line 128: Line 137:
 
</MainModule>
 
</MainModule>
 
</pre>
 
</pre>
|}
 
 
==xquery:parse-uri==
 
 
{| width='100%'
 
|-
 
| width='120' | '''Signatures'''
 
|{{Func|xquery:parse-uri|$uri as xs:string|item()?}}<br />{{Func|xquery:parse-uri|$uri as xs:string, $options as map(*)?|item()?}}<br />
 
|-
 
| '''Summary'''
 
|Parses the XQuery module located at {{Code|$uri}} and returns the resulting query plan. A relative URI will be resolved against the static base URI of the query. The rules for the {{Code|$options}} parameter are the same as for [[#xquery:parse|xquery:parse]].
 
|-
 
| '''Errors'''
 
|Any error that may occur while parsing the query.
 
 
|}
 
|}
  
Line 149: Line 144:
  
 
==xquery:fork-join==
 
==xquery:fork-join==
 +
 +
{{Announce|Updated with Version 11:}} Options added.
  
 
{| width='100%'
 
{| width='100%'
|-
+
|- valign="top"
| width='120' | '''Signatures'''
+
| width='120' | '''Signature'''
|{{Func|xquery:fork-join|$functions as function(*)*|item()*}}
+
|<pre>xquery:fork-join(
|-
+
  $functions as function(*)*,
 +
  $options    as map(*)?      := map { }
 +
) as item()*</pre>
 +
|- valign="top"
 
|'''Summary'''
 
|'''Summary'''
|This function executes the supplied (non-updating) functions in parallel.
+
|This function executes the supplied (non-updating) {{Code|$functions}} in parallel. The following {{Code|$options}} are available:
|-
+
* {{Code|parallel}}: Maximum number of parallel threads. If the value is smaller than {{Code|1}}, or if the option is omitted, the number of available processors is used.
 +
* {{Code|result}}: Suppress or return the function results (default: {{Code|true}}).
 +
* {{Code|errors}}: Ignore or raise errors (default: {{Code|true}}).
 +
|- valign="top"
 
| '''Examples'''
 
| '''Examples'''
 
|
 
|
* The following function sleeps in parallel; it will be finished in 1 second if your system has at least 2 cores:
+
* Request 100 URLs, use at most 8 parallel threads:
<pre class='brush:xquery'>
+
<pre lang='xquery'>
let $f := function() { prof:sleep(1000) }
 
return xquery:fork-join(($f, $f))
 
</pre>
 
* In the following query, up to four URLs will be requested in parallel:
 
<pre class='brush:xquery'>
 
 
xquery:fork-join(
 
xquery:fork-join(
   for $segment in 1 to 4
+
   for $segment in 1 to 100
 
   let $url := 'http://url.com/path/' || $segment
 
   let $url := 'http://url.com/path/' || $segment
   return function() { http:send-request((), $url) }
+
   return function() { http:send-request((), $url) },
 +
  map { 'parallel': 8 }
 
)
 
)
 
</pre>
 
</pre>
|-
+
* 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 $f := function() { prof:sleep(1000) }
 +
return xquery:fork-join(($f, $f))
 +
</pre>
 +
|- valign="top"
 
|'''Errors'''
 
|'''Errors'''
 
|{{Error|error|#Errors}} an unexpected error occurred.
 
|{{Error|error|#Errors}} an unexpected error occurred.
Line 183: Line 187:
 
! width="110"|Code
 
! width="110"|Code
 
|Description
 
|Description
|-
+
|- valign="top"
 
|{{Code|permission}}
 
|{{Code|permission}}
 
|Insufficient permissions for evaluating the query.
 
|Insufficient permissions for evaluating the query.
|-
+
|- valign="top"
 
|{{Code|update}}
 
|{{Code|update}}
 
|[[XQuery Update#Updating Expressions|updating expression]] found or expected.
 
|[[XQuery Update#Updating Expressions|updating expression]] found or expected.
|-
+
|- valign="top"
 
|{{Code|timeout}}
 
|{{Code|timeout}}
 
|Query execution exceeded timeout.
 
|Query execution exceeded timeout.
|-
+
|- valign="top"
 
|{{Code|memory}}
 
|{{Code|memory}}
 
|Query execution exceeded memory limit.
 
|Query execution exceeded memory limit.
|-
+
|- valign="top"
 
|{{Code|nested}}
 
|{{Code|nested}}
 
|Nested query evaluation is not allowed.
 
|Nested query evaluation is not allowed.
|-
+
|- valign="top"
 
|{{Code|error}}
 
|{{Code|error}}
 
|An unexpected error occurred.
 
|An unexpected error occurred.
Line 204: Line 208:
  
 
=Changelog=
 
=Changelog=
 +
 +
;Version 11
 +
 +
* Updated: {{Function||xquery:fork-join}}: Options added.
 +
* Updated: The Clark notation was replaced with the [[XQuery 3.0#Expanded QNames|Expanded QNames]] notation.
 +
 +
;Version 10
 +
 +
* Deleted: xquery:parse-uri (merged with {{Function||xquery:parse}})
 +
* Updated: {{Function||xquery:parse}}: {{$query}} can additionally be of type {{Code|xs:anyURI}}.
  
 
;Version 9.2
 
;Version 9.2
  
* Deleted: xquery:invoke, xquery:invoke-update (merged with [[#xquery:eval|xquery:eval]] and [[#xquery:eval-update|xquery:eval-update]])
+
* Deleted: xquery:invoke, xquery:invoke-update (merged with {{Function||xquery:eval}} and {{Function||xquery:eval-update}})
  
 
;Version 9.0
 
;Version 9.0
  
* Added: [[#xquery:invoke-update|xquery:invoke-update]]
+
* Added: {{Function||xquery:invoke-update}}
* Updated: [[#xquery:eval|xquery:eval]]: {{Code|pass}} option added
+
* Updated: {{Function||xquery:eval}}: {{Code|pass}} option added
* Updated: [[#xquery:parse|xquery:parse]], [[#xquery:parse-uri|xquery:parse-uri]]: {{Code|base-uri}} option added
+
* Updated: {{Function||xquery:parse}}, {{Function||xquery:parse-uri}}: {{Code|base-uri}} option added
* Updated: xquery:update renamed to [[#xquery:eval-update|xquery:eval-update]]
+
* Updated: xquery:update renamed to {{Function||xquery:eval-update}}
 
* Updated: error codes updated; errors now use the module namespace
 
* Updated: error codes updated; errors now use the module namespace
  
 
;Version 8.5
 
;Version 8.5
  
* Added: [[#xquery:fork-join|xquery:fork-join]]
+
* Added: {{Function||xquery:fork-join}}
* Updated: [[#xquery:eval|xquery:eval]]: {{Code|base-uri}} option added
+
* Updated: {{Function||xquery:eval}}: {{Code|base-uri}} option added
 
* Updated: Relative URIs will always be resolved against the static base URI of the query
 
* Updated: Relative URIs will always be resolved against the static base URI of the query
 
* Deleted: xquery:type (moved to [[Profiling Module]])
 
* Deleted: xquery:type (moved to [[Profiling Module]])
Line 226: Line 240:
 
;Version 8.4
 
;Version 8.4
  
* Added: [[#xquery:parse-uri|xquery:parse-uri]]
+
* Added: {{Function||xquery:parse-uri}}
* Updated: [[#xquery:parse|xquery:parse]]: {{Code|pass}} option added
+
* Updated: {{Function||xquery:parse}}: {{Code|pass}} option added
  
 
;Version 8.0
 
;Version 8.0
  
* Added: xquery:update, [[#xquery:parse|xquery:parse]]
+
* Added: xquery:update, {{Function||xquery:parse}}
 
* Deleted: xquery:evaluate (opened databases will now be closed by main query)
 
* Deleted: xquery:evaluate (opened databases will now be closed by main query)
  
Line 240: Line 254:
 
;Version 7.8
 
;Version 7.8
  
* Added: [[#xquery:evaluate|xquery:evaluate]]
+
* Added: {{Function||xquery:evaluate}}
 
* Updated: used variables must be explicitly declared in the query string.
 
* 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.
 
This module was introduced with Version 7.3. Functions have been adopted from the obsolete Utility Module.

Latest revision as of 17:39, 1 December 2023

This XQuery Module contains functions for parsing and evaluating XQuery strings at runtime, and to run code in parallel.

Conventions[edit]

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[edit]

xquery:eval[edit]

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 $bindings. The specified keys must be QNames or strings:

  • If a key is a QName, it will be directly adopted as variable name.
  • It a key is a string, it may be prefixed with a dollar sign. Namespace can be specified using the Expanded QNames notation.
  • If the specified string is empty, the value will be bound to the context item.

The $options parameter contains evaluation options:

  • permission: the query will be evaluated with the specified permissions (see User Management).
  • timeout: query execution will be interrupted after the specified number of seconds.
  • memory: query execution will be interrupted if the specified number of megabytes will be exceeded. This check works best if only one process is running at the same time. Moreover, please note that this option enforces garbage collection, so it will take some additional time, and it requires GC to be enabled in your JVM.
  • base-uri: set base-uri property for the query. Overwrites the base URI of the query; will be used when resolving relative URIs by functions such as fn:doc.
  • pass: passes on the original error info (line and column number, optional file uri). By default, this option is false.
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("1+3") returns 4.
  • If a URI is supplied, the query in the specified file will be evaluated:
xquery:eval(xs:anyURI('cleanup.xq'))
  • You can bind the context and e.g. operate on a certain database only:
xquery:eval("//country", map { '': db:get('factbook') })
  • The following expressions use strings as keys. All of them return 'XML':
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' }
)
  • The following expressions use QNames as keys. All of them return '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[edit]

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
  • Removes entries from a temporary databases and returns an info string:
xquery:eval-update("
  delete node db:get('tmp')/*,
  update:output('TEMPORARY DATABASE WAS CLEANED UP')
")

Parsing[edit]

xquery:parse[edit]

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:
  • compile: additionally compiles the query after parsing it. By default, this option is false.
  • plan: returns an XML representation of the internal query plan. By default, this option is true. The naming of the expressions in the query plan may change over time
  • pass: by default, the option is 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.
  • base-uri: set base-uri property for the query. This URI will be used when resolving relative URIs by functions such as fn:doc.
Errors Any error that may occur while parsing the query.
Examples
  • xquery:parse("1 + 3") returns:
<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[edit]

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[edit]

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:
  • parallel: Maximum number of parallel threads. If the value is smaller than 1, or if the option is omitted, the number of available processors is used.
  • result: Suppress or return the function results (default: true).
  • errors: Ignore or raise errors (default: true).
Examples
  • Request 100 URLs, use at most 8 parallel threads:
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 }
)
  • Parallel sleep function calls. The function is expected to finish in 1 second if the system has at least 2 cores:
let $f := function() { prof:sleep(1000) }
return xquery:fork-join(($f, $f))
Errors error: an unexpected error occurred.

Errors[edit]

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[edit]

Version 11
Version 10
Version 9.2
Version 9.0
Version 8.5
Version 8.4
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.