XQuery Module

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

Template:Mark $options argument added.

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 $query as XQuery expression at runtime 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, the values can be arbitrary item sequences: variables specified as QNames will be directly interpreted as variable name. variables specified as xs:string 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. 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:evaluate

Template:Mark $options argument added.

Signatures	xquery:evaluate($query as xs:string) as item()* xquery:evaluate($query as xs:string, $bindings as map(*)) as item()* xquery:evaluate($query as xs:string, $bindings as map(*), $options as item()) as item()*
Summary	Evaluates $query as XQuery expression at runtime and returns the resulting items. The function differs from xquery:eval in two ways: All items will be directly returned and not duplicated. This way, queries will be evaluated faster, and database nodes will retain their node identity. In exchange, it is not possible to open new databases.
Errors	BXXQ0001: the query contains updating expressions. BXXQ0002: the addressed database cannot be opened. BXXQ0003: insufficient permissions for evaluating the query. BXXQ0004: query execution exceeded timeout. FOTY0013: the expression yields function items.

xquery:invoke

Template:Mark $options argument added.

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	A dynamically evaluated query must not contain updating expressions.
BXXQ0002	The addressed database cannot be opened.
BXXQ0003	Insufficient permissions for evaluating the query.
BXXQ0004	Query execution exceeded timeout.

Changelog

Version 7.8.2

• $options argument added to functions.

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.