Difference between revisions of "XQuery Module"

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|-
 
|-
 
| '''Summary'''
 
| '''Summary'''
−
|Evaluates {{Code|$query}} as XQuery expression at runtime and returns the resulting items.<br/>The evaluated query has its own query context. If a returned node is stored in a database, a main-memory copy will be returned as result, because the referenced database is closed after query execution and will not be accessible anymore.<br />Variables and context items can be declared via {{Code|$bindings}}. The specified keys must be QNames or strings:
+
|Evaluates the supplied {{Code|$query}} string as XQuery expression and returns the resulting items.<br/>The evaluated query has its own query context. If a returned node is stored in a database, a main-memory copy will be returned as result, because the referenced database is closed after query execution and will not be accessible anymore.<br />Variables and context items can be declared via {{Code|$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 [http://www.jclark.com/xml/xmlns.htm Clark Notation].
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| '''Errors'''
 
| '''Errors'''
 
|{{Error|BXXQ0002|#Errors}} the query contains no [[XQuery Update#Updating Expressions|updating expressions]].<br/>{{Error|BXXQ0003|#Errors}} insufficient permissions for evaluating the query.<br/>{{Error|BXXQ0004|#Errors}} query execution exceeded timeout or memory constraints.<br/>{{Error|FOTY0013|#Errors}} the expression yields function items.
 
|{{Error|BXXQ0002|#Errors}} the query contains no [[XQuery Update#Updating Expressions|updating expressions]].<br/>{{Error|BXXQ0003|#Errors}} insufficient permissions for evaluating the query.<br/>{{Error|BXXQ0004|#Errors}} query execution exceeded timeout or memory constraints.<br/>{{Error|FOTY0013|#Errors}} the expression yields function items.
 +
|}
 +
 +
==xquery:parse==
 +
 +
{| width='100%'
 +
|-
 +
| width='120' | '''Signatures'''
 +
|{{Func|xquery:parse|$query as xs:string|item()*}}<br />{{Func|xquery:eval|$query as xs:string, $options as item()|item()}}<br />
 +
|-
 +
| '''Summary'''
 +
|Parses the specified {{Code|$query}} string as XQuery module and returns information on the resulting query plan (please note that the naming of the expressions in the query plan may change over time). The {{Code|$options}} parameters can be specified in two ways:
 +
* as children of an {{Code|<xquery:options/>}} element:
 +
<pre class="brush:xml">
 +
<xquery:options>
 +
  <xquery:compile value="true"/>
 +
</xquery:options>
 +
</pre>
 +
* as map, which contains all key/value pairs:
 +
<pre class="brush:xml">
 +
map { "compile": true() }
 +
</pre>
 +
The following options are available:
 +
* {{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}}.
 +
|-
 +
| '''Errors'''
 +
|{{Error|BXXQ0003|#Errors}} insufficient permissions for evaluating the query.
 +
|-
 +
| '''Examples'''
 +
|
 +
* {{Code|xquery:parse("1 + 3")}} returns:
 +
<pre class='brush:xml'>
 +
<MainModule updating="false">
 +
  <QueryPlan compiled="false">
 +
    <Arith op="+">
 +
      <Int value="1" type="xs:integer"/>
 +
      <Int value="3" type="xs:integer"/>
 +
    </Arith>
 +
  </QueryPlan>
 +
</MainModule>
 +
</pre>
 
|}
 
|}
  
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;Version 8.0
 
;Version 8.0
−
* Added: [[#xquery:update|xquery:update]]
+
* Added: [[#xquery:update|xquery:update]], [[#xquery:parse|xquery:parse]]
 
* Deleted: [[#xquery:evaluate|xquery:evaluate]] (opened databases will now be closed by main query)
 
* Deleted: [[#xquery:evaluate|xquery:evaluate]] (opened databases will now be closed by main query)
  

Revision as of 20:14, 23 December 2014

This XQuery Module contains functions for evaluating XQuery strings and modules at runtime.

Conventions

All functions in this module are assigned to the http://basex.org/modules/xquery namespace, which is statically bound to the xquery prefix.
All errors are assigned to the http://basex.org/errors namespace, which is statically bound to the bxerr prefix.

Functions

xquery:eval

Signatures xquery:eval($query as xs:string) as item()*
xquery:eval($query as xs:string, $bindings as map(*)) as item()*
xquery:eval($query as xs:string, $bindings as map(*), $options as item()) as item()
Summary Evaluates the supplied $query string as XQuery expression and returns the resulting items.
The evaluated query has its own query context. If a returned node is stored in a database, a main-memory copy will be returned as result, because the referenced database is closed after query execution and will not be accessible anymore.
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 Clark Notation.
  • If the specified string is empty, the value will be bound to the context item.

The $options parameter contains evaluation options, which can either be specified

  • as children of an <xquery:options/> element:
<xquery:options>
  <xquery:permission value="none"/>
</xquery:options>
  • as map, which contains all key/value pairs:
map { "permission": "none" }

The following options are available:

  • 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.
Errors BXXQ0001: the query contains updating expressions.
BXXQ0003: insufficient permissions for evaluating the query.
BXXQ0004: query execution exceeded timeout or memory constraints.
FOTY0013: the expression yields function items.
Examples
  • xquery:eval("1+3") returns 4.
  • You can bind the context and e.g. operate on a certain database only:
xquery:eval("//country", map { '': db:open('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:update

Template:Mark

Signatures xquery:update($query as xs:string) as item()*
xquery:update($query as xs:string, $bindings as map(*)) as item()*
xquery:update($query as xs:string, $bindings as map(*), $options as item()) as item()
Summary Evaluates $query as updating XQuery expression at runtime.
All updates will be added to the Pending Update List of the main query and performed after the evaluation of the main query.
Errors BXXQ0002: the query contains no updating expressions.
BXXQ0003: insufficient permissions for evaluating the query.
BXXQ0004: query execution exceeded timeout or memory constraints.
FOTY0013: the expression yields function items.

xquery:parse

Signatures xquery:parse($query as xs:string) as item()*
xquery:eval($query as xs:string, $options as item()) as item()
Summary Parses the specified $query string as XQuery module and returns information on the resulting query plan (please note that the naming of the expressions in the query plan may change over time). The $options parameters can be specified in two ways:
  • as children of an <xquery:options/> element:
<xquery:options>
  <xquery:compile value="true"/>
</xquery:options>
  • as map, which contains all key/value pairs:
map { "compile": true() }

The following options are available:

  • 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.
Errors BXXQ0003: insufficient permissions for evaluating 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>

xquery:invoke

Signatures xquery:invoke($uri as xs:string) as item()*
xquery:invoke($uri as xs:string, $bindings as map(*)) as item()*
xquery:invoke($uri as xs:string, $bindings as map(*), $options as item()) as item()*
Summary Opens $uri as file, evaluates it as XQuery expression at runtime, and returns the resulting items. Database nodes in the result will be copied and returned instead.
The semantics of the $bindings and $options parameters is the same as for xquery:eval.
Errors BXXQ0001: the expression contains updating expressions.
BXXQ0003: insufficient permissions for evaluating the query.
BXXQ0004: query execution exceeded timeout.
FOTY0013: the expression yields function items.

xquery:type

Signatures xquery:type($expr as item()*) as item()*
Summary Similar to fn:trace($expr, $msg), but instead of a user-defined message, it emits the compile-time type and estimated result size of its argument.

Errors

Code Description
BXXQ0001 The specified query contains updating expressions.
BXXQ0002 The specified query contains no updating expressions.
BXXQ0003 Insufficient permissions for evaluating the query.
BXXQ0004 Query execution exceeded timeout.

Changelog

Version 8.0
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.

Retrieved from "https://old.docs.basex.org/index.php?title=XQuery_Module&oldid=11250"