XQuery Module

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

Since Template:Mark, used variables must be explicitly declared in the query string via the declare variable statement.

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()*
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 $bindings. The specified keys must be QNames or strings, the values can be arbitrary item sequences: variables specified as QNames will be directly interpreted as variable name. variables specified as xs:string may be prefixed with a dollar sign. Namespace can be specified using the Clark Notation. If the specified string is empty, the value will be bound to the context item.
Errors	BXXQ0001: the query contains updating expressions. FOTY0013: the expression yields function items.
Examples	xquery:eval("1+3") returns 4. You can bind the context and e.g. operate on a certain database only: xquery:eval("//country", map{ '' := db:open('factbook') }) The following expressions use strings as keys. All of them return 'XML': xquery:eval(".", map{ '' := 'XML' }) xquery:eval("$xml", map{ 'xml' := 'XML' }), xquery:eval("$xml", map{ '$xml' := 'XML' }), xquery:eval("declare namespace pref='URI'; $pref:xml", map{ '{URI}xml' := 'XML' }), The following expressions use QNames as keys. All of them return 'XML': declare namespace pref = 'URI'; xquery:eval("$xml", map{ xs:QName('xml') := 'XML' }) xquery:eval("declare namespace pref='URI'; $pref:xml", map{ xs:QName('pref:xml') := 'XML' }),

xquery:evaluate

Signatures	xquery:evaluate($query as xs:string) as item()* xquery:evaluate($query as xs:string, $bindings as map(*)) 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. FOTY0013: the expression yields function items.

xquery:invoke

Signatures	xquery:invoke($uri as xs:string) as item()* xquery:invoke($uri as xs:string, $bindings as map(*)) 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 parameter is the same as for xquery:eval.
Errors	BXXQ0001: the expression contains updating expressions. 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.

Changelog

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.