XQuery Module
This XQuery Module contains functions for evaluating XQuery strings and modules at runtime.
Contents
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.
Functions
xquery:eval
Template:Mark pass
option 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 map(xs:string, xs:string)) 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:
The
|
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("//country", map { '': db:open('factbook') })
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' } )
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, $vars) |
xquery:eval-update
Template:Mark Renamed (old name: xquery:update)
Signatures | xquery:eval-update($query as xs:string) as item()* xquery:eval-update($query as xs:string, $bindings as map(*)?) as item()* xquery:eval-update($query as xs:string, $bindings as map(*)?, $options as map(xs:string, xs:string)) 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. The rules of the $bindings and $options parameters are the same as for xquery:eval.
|
Errors | update : the query contains no updating expressions.permission : insufficient permissions for evaluating the query.timeout : query execution exceeded timeout.limit : query execution exceeded memory limit.nested : nested query evaluation is not allowed.Any other error that may occur while evaluating the query. |
xquery:invoke
Signatures | xquery:invoke($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 map(*)) as item()* |
Summary | Evaluates the XQuery module located at $uri at runtime and returns the resulting items. A relative URI will be resolved against the static base URI of the query.The rules of the $bindings and $options parameters are the same as for xquery:eval.
|
Errors | update : the expression contains updating expressions.permission : insufficient permissions for evaluating the query.timeout : query execution exceeded timeout.nested : nested query evaluation is not allowed.Any other error that may occur while evaluating the query. |
xquery:invoke-update
Signatures | xquery:invoke-update($uri as xs:string) as item()* xquery:invoke-update($uri as xs:string, $bindings as map(*)?) as item()* xquery:invoke-update($uri as xs:string, $bindings as map(*)?, $options as map(*)) as item()* |
Summary | Evaluates the updating XQuery module located at $uri at runtime. A relative URI will be resolved against the static base URI of the query.The rules of the $bindings and $options parameters are the same as for xquery:eval.
|
Errors | update : the expression contains no updating expressions.permission : insufficient permissions for evaluating the query.timeout : query execution exceeded timeout.nested : nested query evaluation is not allowed.Any other error that may occur while evaluating the query. |
xquery:parse
Template:Mark base-uri
option added.
Signatures | xquery:parse($query as xs:string) as item()? xquery:parse($query as xs:string, $options as map(*)) as item()? |
Summary | Parses the specified $query string as XQuery module and returns the resulting query plan. The $options parameter influences the output:
|
Errors | Any error that may occur while parsing the query. |
Examples |
<MainModule updating="false"> <QueryPlan compiled="false"> <Arith op="+"> <Int value="1" type="xs:integer"/> <Int value="3" type="xs:integer"/> </Arith> </QueryPlan> </MainModule> |
xquery:parse-uri
Template:Mark base-uri
option added.
Signatures | xquery:parse-uri($uri as xs:string) as item()? xquery:parse-uri($uri as xs:string, $options as map(*)) as item()? |
Summary | Parses the XQuery module located at $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 $options parameter are the same as for xquery:parse.
|
Errors | Any error that may occur while parsing the query. |
Parallelized Execution
Parallel query execution is recommendable if you have various calls that require a lot of time, but cannot be sped up by rewriting the code. This is e. g. the case if external URLs are called. If you are parallelizing local data reads (such as the access to a database), single-threaded queries will usually be faster, because parallelized access to disk data often results in randomized access patterns, which can hardly be optimized by the caching strategies of HD, SSD or operating system.
xquery:fork-join
Signatures | xquery:fork-join($functions as function(*)*) as item()*
|
Summary | This function executes the supplied (non-updating) functions in parallel. |
Examples |
let $f := function() { prof:sleep(1000) } return xquery:fork-join(($f, $f))
let $funcs := for $segment in 1 to 4 let $url := 'http://url.com/path' || $segment return function() { http:send-request((), $url) } return xquery:fork-join($funcs) |
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 9.0
- Added: xquery:invoke-update
- Updated: xquery:eval:
pass
option added - Updated: xquery:parse, xquery:parse-uri:
base-uri
option added - Updated: xquery:update renamed to xquery:eval-update
- Updated: error codes updated; errors now use the module namespace
- Version 8.5
- Added: xquery:fork-join
- Updated: xquery:eval:
base-uri
option added - Updated: Relative URIs will always be resolved against the static base URI of the query
- Deleted: xquery:type (moved to Profiling Module
- Version 8.4
- Added: xquery:parse-uri
- Updated: xquery:parse:
pass
option added
- 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.