Difference between revisions of "XQuery Module"

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This [[Module Library|XQuery Module]] contains functions for evaluating XQuery strings and modules at runtime.
+
This [[Module Library|XQuery Module]] contains functions for parsing and evaluating XQuery strings at runtime, and to run code in parallel.
  
 
=Conventions=
 
=Conventions=
 
{{Mark|Updated with Version 9.0}}:
 
  
 
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/>
  
=Functions=
+
=Evaluation=
 
 
This [[Module Library|XQuery Module]] contains functions to access relational databases from XQuery using SQL. With this module, you can execute query, update and prepared statements, and the result sets are returned as sequences of XML elements representing tuples. Each element has children representing the columns returned by the SQL statement.
 
 
 
This module uses JDBC to connect to a SQL server. Hence, your JDBC driver will need to be added to the classpath, too. If you work with the full distributions of BaseX, you can copy the driver into the {{Code|lib}} directory. To connect to MySQL, for example, download the [https://dev.mysql.com/downloads/connector/j/ Connector/J Driver] and extract the archive into this directory.
 
 
 
=Conventions=
 
 
 
{{Mark|Updated with Version 9.0}}:
 
 
 
All functions and errors in this module are assigned to the <code><nowiki>http://basex.org/modules/sql</nowiki></code> namespace, which is statically bound to the {{Code|sql}} prefix.<br/>
 
 
 
=Functions=
 
  
==sql:init==
+
==xquery:eval==
  
 
{| width='100%'
 
{| width='100%'
|-
+
|- valign="top"
 
| width='120' | '''Signatures'''
 
| width='120' | '''Signatures'''
|{{Func|sql:init|$class as xs:string|empty-sequence()}}
+
|{{Func|xquery:eval|$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 />
|-
+
|- valign="top"
 
| '''Summary'''
 
| '''Summary'''
|This function initializes a JDBC driver specified via {{Code|$class}}. This step might be superfluous if the SQL database is not embedded.<br/ >
+
|Evaluates the supplied {{Code|$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|$bindings}}. The specified keys must be QNames or strings:
 +
* If a key is a QName, it will be directly adopted as variable name.
 +
* It a key is a string, it may be prefixed with a dollar sign. Namespace can be specified using the [http://www.jclark.com/xml/xmlns.htm Clark Notation].
 +
* If the specified string is empty, the value will be bound to the context item.
 +
The {{Code|$options}} parameter contains evaluation options:
 +
* {{Code|permission}}: the query will be evaluated with the specified permissions (see [[User Management]]).
 +
* {{Code|timeout}}: query execution will be interrupted after the specified number of seconds.
 +
* {{Code|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.
 +
* {{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}}.
 +
|- valign="top"
 
| '''Errors'''
 
| '''Errors'''
|{{Error|init|XQuery Errors#SQL Functions Errors}} the specified driver is not found.
+
|{{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"
 
 
==sql:connect==
 
 
 
{| width='100%'
 
|-
 
| width='120' | '''Signatures'''
 
|{{Func|sql:connect|$url as xs:string|xs:anyURI}}<br/ >{{Func|sql:connect|$url as xs:string, $user as xs:string, $password as xs:string|xs:anyURI}}<br/ >{{Func|sql:connect|$url as xs:string, $user as xs:string, $password as xs:string, $options as map(*)|xs:anyURI}}<br/ >
 
|-
 
| '''Summary'''
 
|This function establishes a connection to a relational database and returns a connection id. The parameter {{Code|$url}} is the URL of the database and shall be of the form: {{Code|jdbc:<driver name>:[//<server>[/<database>]]}}. If the parameters {{Code|$user}} and {{Code|$password}} are specified, they are used as credentials for connecting to the database. The {{Code|$options}} parameter can be used to set connection options.
 
|-
 
| '''Errors'''
 
|{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs, e.g. missing JDBC driver or not existing relation.
 
|-
 
 
| '''Examples'''
 
| '''Examples'''
|Connects to an SQL Server and sets autocommit to {{Code|true}}:
+
|
<pre class="brush:xquery">
+
* {{Code|xquery:eval("1+3")}} returns {{Code|4}}.<br />
sql:connect('dbc:sqlserver://DBServer', map { 'autocommit': true() })
+
* If a URI is supplied, the query in the specified file will be evaluated:
</pre>
+
<syntaxhighlight lang="xquery">
|}
+
xquery:eval(xs:anyURI('cleanup.xq'))
 
+
</syntaxhighlight>
==sql:execute==
+
* You can bind the context and e.g. operate on a certain database only:<br />
 
+
<syntaxhighlight lang="xquery">
{{Mark|Updated with Version 9.0}}: Return update count for updating statements. {{Code|$options}} argument added.
+
xquery:eval("//country", map { '': db:get('factbook') })
 
+
</syntaxhighlight>
{| width='100%'
+
* The following expressions use strings as keys. All of them return 'XML':<br/>
|-
+
<syntaxhighlight lang="xquery">
| width='120' | '''Signatures'''
+
xquery:eval(".", map { '': 'XML' }),
|{{Func|sql:execute|$id as xs:anyURI, $statement as xs:string|item()*}}<br/>{{Func|sql:execute|$id as xs:anyURI, $statement as xs:string, $options as map(*)|item()*}}
 
|-
 
| '''Summary'''
 
| This function executes an SQL {{Code|$statement}}, using the connection with the specified {{Code|$id}}. The returned result depends on the kind of statement:
 
* If an update statement was executed, the number of updated rows will be returned as integer.
 
* Otherwise, an XML representation of all results will be returned.
 
With {{Code|$options}}, the following parameter can be set:
 
* {{Code|timeout}}: query execution will be interrupted after the specified number of seconds.
 
|-
 
| '''Errors'''
 
|{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs, e.g. not existing relation is retrieved.<br/ >{{Error|id|XQuery Errors#SQL Functions Errors}} the specified connection does not exist.<br/ >
 
|}
 
 
 
==sql:execute-prepared==
 
 
 
{{Mark|Updated with Version 9.0}}: Return update count for updating statements.
 
 
 
{| width='100%'
 
|-
 
| width='120' | '''Signatures'''
 
|{{Func|sql:execute-prepared|$id as xs:anyURI, $params as element(sql:parameters)|item()*}}<br/>{{Func|sql:execute-prepared|$id as xs:anyURI, $params as element(sql:parameters), $options as map(*)|item()*}}
 
|-
 
| '''Summary'''
 
| This function executes a prepared statement with the specified {{Code|$id}}. The output format is identical to [[#sql:execute|sql:execute]]. The optional parameter {{Code|$params}} is an element {{Code|<sql:parameters/>}} representing the parameters for a prepared statement along with their types and values. The following schema shall be used:<br/ >
 
<pre class="brush:xquery">
 
element sql:parameters {
 
  element sql:parameter {
 
    attribute type { "int" | "string" | "boolean" | "date" | "double" |
 
      "float" | "short" | "time" | "timestamp" | "sqlxml" },
 
    attribute null { "true" | "false" }?,
 
    text
 
  }+
 
}?
 
</pre>
 
With {{Code|$options}}, the following parameter can be set:
 
* {{Code|timeout}}: query execution will be interrupted after the specified number of seconds.
 
|-
 
| '''Errors'''
 
|{{Error|attribute|XQuery Errors#SQL Functions Errors}} an attribute different from {{Code|type}} and {{Code|null}} is set for a {{Code|<sql:parameter/>}} element.<br/ >{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs, e.g. not existing relation is retrieved.<br/ >{{Error|id|XQuery Errors#SQL Functions Errors}} the specified connection does not exist.<br/ >{{Error|parameters|XQuery Errors#SQL Functions Errors}} wrong number of {{Code|<sql:parameter/>}} elements, or parameter type is not specified.<br/>{{Error|type|XQuery Errors#SQL Functions Errors}} the value of a parameter cannot be converted to the specified format.
 
|}
 
 
 
==sql:prepare==
 
 
 
{| width='100%'
 
|-
 
| width='120' | '''Signatures'''
 
|{{Func|sql:prepare|$id as xs:anyURI, $statement as xs:string|xs:anyURI}}
 
|-
 
| '''Summary'''
 
|This function prepares an SQL {{Code|$statement}}, using the specified connection {{Code|$id}}, and returns the id reference to this statement. The statement is a string with one or more '?' placeholders. If the value of a field has to be set to {{Code|NULL}}, then the attribute {{Code|null}} of the {{Code|<sql:parameter/>}} element must be {{Code|true}}.
 
|-
 
| '''Errors'''
 
|{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs.<br/ >{{Error|id|XQuery Errors#SQL Functions Errors}} the specified connection does not exist.<br/ >
 
|}
 
  
==sql:commit==
+
xquery:eval("declare variable $xml external; $xml", map { 'xml': 'XML' }),
  
{| width='100%'
+
xquery:eval(
|-
+
  "declare namespace pref='URI';
| width='120' | '''Signatures'''
+
  declare variable $pref:xml external;
|{{Func|sql:commit|$id as xs:anyURI|empty-sequence()}}
+
  $pref:xml",
|-
+
  map { '{URI}xml': 'XML' }
| '''Summary'''
 
| This function commits the changes made to a relational database, using the specified connection {{Code|$id}}.
 
|-
 
| '''Errors'''
 
|{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs.<br/ >{{Error|id|XQuery Errors#SQL Functions Errors}} the specified connection does not exist.<br/ >
 
|}
 
 
 
==sql:rollback==
 
 
 
{| width='100%'
 
|-
 
| width='120' | '''Signatures'''
 
|{{Func|sql:rollback|$id as xs:anyURI|empty-sequence()}}
 
|-
 
| '''Summary'''
 
| This function rolls back the changes made to a relational database, using the specified connection {{Code|$id}}.
 
|-
 
| '''Errors'''
 
|{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs.<br/ >{{Error|id|XQuery Errors#SQL Functions Errors}} the specified connection does not exist.<br/ >
 
|}
 
 
 
==sql:close==
 
 
 
{| width='100%'
 
|-
 
| width='120' | '''Signatures'''
 
|{{Func|sql:close|$id as xs:anyURI|empty-sequence()}}
 
|-
 
| '''Summary'''
 
| This function closes a database connection with the specified {{Code|$id}}.<br/>Opened connections will automatically be closed after the XQuery expression has been evaluated, but in order to save memory, it is always recommendable to close connections that are not used anymore.
 
|-
 
| '''Errors'''
 
|{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs.<br/ >{{Error|id|XQuery Errors#SQL Functions Errors}} the specified connection does not exist.<br/ >
 
|}
 
 
 
=Examples=
 
 
 
==Direct queries==
 
 
 
A simple select statement can be executed as follows:
 
 
 
<pre class="brush:xquery">
 
let $id := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")
 
return sql:execute($id, "SELECT * FROM coffees WHERE price < 10")
 
</pre>
 
 
 
The result may look like:
 
 
 
<pre class="brush:xml">
 
<sql:row xmlns:sql="http://basex.org/modules/sql">
 
  <sql:column name="cof_name">French_Roast</sql:column>
 
  <sql:column name="sup_id">49</sql:column>
 
  <sql:column name="price">9.5</sql:column>
 
  <sql:column name="sales">15</sql:column>
 
  <sql:column name="total">30</sql:column>
 
</sql:row>
 
<sql:row xmlns:sql="http://basex.org/modules/sql">
 
  <sql:column name="cof_name">French_Roast_Decaf</sql:column>
 
  <sql:column name="sup_id">49</sql:column>
 
  <sql:column name="price">7.5</sql:column>
 
  <sql:column name="sales">10</sql:column>
 
  <sql:column name="total">14</sql:column>
 
</sql:row>
 
</pre>
 
 
 
==Prepared Statements==
 
 
 
A prepared select statement can be executed in the following way:
 
 
 
<pre class="brush:xquery">
 
(: Establish a connection :)
 
let $conn := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")
 
(: Obtain a handle to a prepared statement :)
 
let $prep := sql:prepare($conn, "SELECT * FROM coffees WHERE price < ? AND cof_name = ?")
 
(: Values and types of prepared statement parameters :)
 
let $params := <sql:parameters>
 
                <sql:parameter type='double'>10</sql:parameter>
 
                <sql:parameter type='string'>French_Roast</sql:parameter>
 
              </sql:parameters>
 
(: Execute prepared statement :)
 
return sql:execute-prepared($prep, $params)
 
</pre>
 
 
 
==SQLite==
 
 
 
The following expression demonstrates how SQLite can be addressed using the [http://bitbucket.org/xerial/sqlite-jdbc Xerial SQLite JDBC driver]:
 
 
 
<pre class="brush:xquery">
 
(: Initialize driver :)
 
sql:init("org.sqlite.JDBC"),
 
(: Establish a connection :)
 
let $conn := sql:connect("jdbc:sqlite:database.db")
 
return (
 
  (: Create a new table :)
 
  sql:execute($conn, "drop table if exists person"),
 
  sql:execute($conn, "create table person (id integer, name string)"),
 
  (: Run 10 updates :)
 
  for $i in 1 to 10
 
  let $q := "insert into person values(" || $i || ", '" || $i || "')"
 
  return sql:execute($conn, $q),
 
  (: Return table contents :)
 
  sql:execute($conn, "select * from person")
 
 
)
 
)
</pre>
+
</syntaxhighlight>
 
+
* The following expressions use QNames as keys. All of them return 'XML':<br/>
=Errors=
+
<syntaxhighlight lang="xquery">
 +
declare namespace pref = 'URI';
  
{{Mark|Updated with Version 9.0}}:
+
xquery:eval("declare variable $xml external; $xml", map { xs:QName('xml'): 'XML' }),
  
{| class="wikitable" width="100%"
+
let $query := "declare namespace pref='URI';
! width="110"|Code
+
              declare variable $pref:xml external;
|Description
+
              $pref:xml"
|-
+
let $vars := map { xs:QName('pref:xml'): 'XML' }
|{{Code|attribute}}
+
return xquery:eval($query, $vars)
|An attribute different from {{Code|type}} and {{Code|null}} is set for a {{Code|&lt;sql:parameter/&gt;}} element.
+
</syntaxhighlight>
|-
 
|{{Code|error}}
 
|An SQL exception occurred.
 
|-
 
|{{Code|id}}
 
|A connection does not exist.
 
|-
 
|{{Code|init}}
 
|A database driver is not found.
 
|-
 
|{{Code|parameters}}
 
|Wrong number of {{Code|&lt;sql:parameter/&gt;}} elements, or parameter type is not specified.
 
|-
 
|{{Code|type}}
 
|The value of a parameter cannot be converted to the specified format.
 
 
|}
 
|}
 
=Changelog=
 
 
;Version 9.0
 
 
* Updated: [[#sql:execute|sql:execute]], [[#sql:execute-prepared|sql:execute-prepared]]: Return update count for updating statements. {{Code|$options}} argument added.
 
 
* Updated: Connection ids are URIs now.
 
* Updated: error codes updated; errors now use the module namespace
 
 
;Version 7.5
 
 
* Updated: prepared statements are now executed via [[#sql:execute-prepared|sql:execute-prepared]]
 
 
The module was introduced with Version 7.0.
 
  
 
==xquery:eval-update==
 
==xquery:eval-update==
 
{{Mark|Updated with Version 9.0}}: Renamed (old name: xquery:update)
 
  
 
{| width='100%'
 
{| width='100%'
|-
+
|- valign="top"
 
| width='120' | '''Signatures'''
 
| width='120' | '''Signatures'''
|{{Func|xquery:eval-update|$query as xs:string|item()*}}<br />{{Func|xquery:eval-update|$query as xs:string, $bindings as map(*)?|item()*}}<br />{{Func|xquery:eval-update|$query as xs:string, $bindings as map(*)?, $options as map(xs:string, xs:string)|item()}}<br />
+
|{{Func|xquery:eval-update|$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 />
|-
+
|- valign="top"
 
| '''Summary'''
 
| '''Summary'''
|Evaluates {{Code|$query}} as updating XQuery expression at runtime.<br/>All updates will be added to the [[XQuery Update#Pending Update List|Pending Update List]] of the main query and performed after the evaluation of the main query.<br />The rules of the {{Code|$bindings}} and {{Code|$options}} parameters 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'''
 +
|
 +
* Removes entries from a temporary databases and returns an info string:
 +
<syntaxhighlight lang="xquery">
 +
xquery:eval-update("
 +
  delete node db:get('tmp')/*,
 +
  update:output('TEMPORARY DATABASE WAS CLEANED UP')
 +
")
 +
</syntaxhighlight>
 
|}
 
|}
  
==xquery:invoke==
+
=Parsing=
 
 
{| width='100%'
 
|-
 
| width='120' | '''Signatures'''
 
|{{Func|xquery:invoke|$uri as xs:string|item()*}}<br />{{Func|xquery:invoke|$uri as xs:string, $bindings as map(*)?|item()*}}<br />{{Func|xquery:invoke|$uri as xs:string, $bindings as map(*)?, $options as map(*)|item()*}}<br />
 
|-
 
| '''Summary'''
 
|Evaluates the XQuery module located at {{Code|$uri}} at runtime and returns the resulting items. A relative URI will be resolved against the static base URI of the query.<br />The rules of the {{Code|$bindings}} and {{Code|$options}} parameters are the same as for [[#xquery:eval|xquery:eval]].
 
|-
 
| '''Errors'''
 
|{{Error|update|#Errors}} the expression contains [[XQuery Update#Updating Expressions|updating expressions]].<br/>{{Error|permission|#Errors}} insufficient permissions for evaluating the query.<br/>{{Error|BXXQ0004|#Errors}} query execution exceeded timeout.<br/>{{Error|nested|#Errors}} nested query evaluation is not allowed.<br/>Any other error that may occur while evaluating the query.
 
|}
 
 
 
==xquery:invoke-update==
 
 
 
{| width='100%'
 
|-
 
| width='120' | '''Signatures'''
 
|{{Func|xquery:invoke-update|$uri as xs:string|item()*}}<br />{{Func|xquery:invoke-update|$uri as xs:string, $bindings as map(*)?|item()*}}<br />{{Func|xquery:invoke-update|$uri as xs:string, $bindings as map(*)?, $options as map(*)|item()*}}<br />
 
|-
 
| '''Summary'''
 
|Evaluates the updating XQuery module located at {{Code|$uri}} at runtime. A relative URI will be resolved against the static base URI of the query.<br />The rules of the {{Code|$bindings}} and {{Code|$options}} parameters are the same as for [[#xquery:eval|xquery:eval]].
 
|-
 
| '''Errors'''
 
|{{Error|update|#Errors}} the expression contains no [[XQuery Update#Updating Expressions|updating expressions]].<br/>{{Error|permission|#Errors}} insufficient permissions for evaluating the query.<br/>{{Error|BXXQ0004|#Errors}} query execution exceeded timeout.<br/>{{Error|nested|#Errors}} nested query evaluation is not allowed.<br/>Any other error that may occur while evaluating the query.
 
|}
 
  
 
==xquery:parse==
 
==xquery:parse==
  
{{Mark|Updated with Version 9.0}}: {{code|base-uri}} option added.
+
{{Announce|Updated with Version 10:}} {{Code|$query}} can additionally be of type {{Code|xs:anyURI}}.
  
 
{| width='100%'
 
{| width='100%'
|-
+
|- valign="top"
 
| width='120' | '''Signatures'''
 
| width='120' | '''Signatures'''
|{{Func|xquery:parse|$query as xs:string|item()?}}<br />{{Func|xquery:parse|$query as xs:string, $options as map(*)|item()?}}<br />
+
|{{Func|xquery:parse|$query as xs:anyAtomicType|item()?}}<br />{{Func|xquery:parse|$query as xs:anyAtomicType, $options as map(*)?|item()?}}<br />
|-
+
|- 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}}: passes on the original error info (line and column number, optional file uri). By default, this option is {{Code|false}}.
+
* {{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'>
+
<syntaxhighlight lang="xml">
 
<MainModule updating="false">
 
<MainModule updating="false">
 
   <QueryPlan compiled="false">
 
   <QueryPlan compiled="false">
Line 346: Line 125:
 
   </QueryPlan>
 
   </QueryPlan>
 
</MainModule>
 
</MainModule>
</pre>
+
</syntaxhighlight>
|}
 
 
 
==xquery:parse-uri==
 
 
 
{{Mark|Updated with Version 9.0}}: {{code|base-uri}} option added.
 
 
 
{| 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.
 
 
|}
 
|}
  
 
=Parallelized Execution=
 
=Parallelized Execution=
  
Parallel query execution is recommendable if you have various calls that require a lot of time, but 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 can hardly be optimized by the caching strategies of HD, SSD or operating system.
+
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==
 
==xquery:fork-join==
  
 
{| width='100%'
 
{| width='100%'
|-
+
|- valign="top"
 
| width='120' | '''Signatures'''
 
| width='120' | '''Signatures'''
 
|{{Func|xquery:fork-join|$functions as function(*)*|item()*}}
 
|{{Func|xquery:fork-join|$functions as function(*)*|item()*}}
|-
+
|- valign="top"
 
|'''Summary'''
 
|'''Summary'''
 
|This function executes the supplied (non-updating) functions in parallel.
 
|This function executes the supplied (non-updating) functions in parallel.
|-
+
|- 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:
 
* The following function sleeps in parallel; it will be finished in 1 second if your system has at least 2 cores:
<pre class='brush:xquery'>
+
<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))
</pre>
+
</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:
<pre class='brush:xquery'>
+
<syntaxhighlight lang="xquery">
let $funcs :=
+
xquery:fork-join(
 
   for $segment in 1 to 4
 
   for $segment in 1 to 4
   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((), $url) }
return xquery:fork-join($funcs)
+
)
</pre>
+
</syntaxhighlight>
|-
+
|- valign="top"
 
|'''Errors'''
 
|'''Errors'''
 
|{{Error|error|#Errors}} an unexpected error occurred.
 
|{{Error|error|#Errors}} an unexpected error occurred.
Line 400: Line 163:
  
 
=Errors=
 
=Errors=
 
{{Mark|Updated with Version 9.0}}:
 
  
 
{| class="wikitable" width="100%"
 
{| class="wikitable" width="100%"
 
! 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 427: Line 188:
  
 
=Changelog=
 
=Changelog=
 +
 +
;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
 +
 +
* 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-uri|xquery:invoke-uri]]
+
* 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]])
  
 
;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|xquery:evaluate]] (opened databases will now be closed by main query)
+
* Deleted: xquery:evaluate (opened databases will now be closed by main query)
  
 
;Version 7.8.2
 
;Version 7.8.2
Line 459: Line 229:
 
;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.

Revision as of 13:20, 20 July 2022

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

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

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 $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:

  • 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:

<syntaxhighlight lang="xquery"> xquery:eval(xs:anyURI('cleanup.xq')) </syntaxhighlight>

  • You can bind the context and e.g. operate on a certain database only:

<syntaxhighlight lang="xquery"> xquery:eval("//country", map { : db:get('factbook') }) </syntaxhighlight>

  • The following expressions use strings as keys. All of them return 'XML':

<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>

  • The following expressions use QNames as keys. All of them return 'XML':

<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
  • Removes entries from a temporary databases and returns an info string:

<syntaxhighlight lang="xquery"> xquery:eval-update("

 delete node db:get('tmp')/*,
 update:output('TEMPORARY DATABASE WAS CLEANED UP')

") </syntaxhighlight>

Parsing

xquery:parse

Updated with Version 10: $query can additionally be of type xs:anyURI.

Signatures xquery:parse($query as xs:anyAtomicType) as item()?
xquery:parse($query as xs:anyAtomicType, $options as 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:

<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>

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
  • 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 $f := function() { prof:sleep(1000) } return xquery:fork-join(($f, $f)) </syntaxhighlight>

  • In the following query, up to four URLs will be requested in parallel:

<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 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.