Difference between revisions of "Update Module"
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− | This [[Module Library|XQuery Module]] | + | This [[Module Library|XQuery Module]] provides additional functions for performing updates and returning results in [[XQuery Update|updating expressions]]. |
=Conventions= | =Conventions= | ||
All functions in this module are assigned to the <code><nowiki>http://basex.org/modules/update</nowiki></code> namespace, which is statically bound to the {{Code|update}} prefix.<br/> | All functions in this module are assigned to the <code><nowiki>http://basex.org/modules/update</nowiki></code> namespace, which is statically bound to the {{Code|update}} prefix.<br/> | ||
+ | |||
+ | Except for {{Function||update:output-cache}}, all functions are ''updating'' and thus comply to the XQuery Update constraints. | ||
+ | |||
+ | =Updates= | ||
+ | |||
+ | ==update:apply== | ||
+ | |||
+ | {| | ||
+ | |- valign="top" | ||
+ | | width='120' | '''Signature''' | ||
+ | |<pre>update:apply( | ||
+ | $function as function(*), | ||
+ | $arguments as array(*) | ||
+ | ) as empty-sequence()</pre> | ||
+ | |- valign="top" | ||
+ | | '''Summary''' | ||
+ | |The updating variant of [[XQuery 3.1#fn:apply|fn:apply]] applies the specified updating <code>$function</code> to the specified <code>$arguments</code>. | ||
+ | |- valign="top" | ||
+ | | '''Examples''' | ||
+ | | | ||
+ | * Creates a new database with an initial document and adds a document to an existing database. | ||
+ | <pre lang='xquery'> | ||
+ | declare %updating function local:update( | ||
+ | $database as xs:string, | ||
+ | $path as xs:string, | ||
+ | $function as %updating function(item(), xs:string) as empty-sequence() | ||
+ | ) as empty-sequence() { | ||
+ | update:apply($function, [ $database, $path ]) | ||
+ | }; | ||
+ | local:update('new-db', 'doc.xml', db:create#2), | ||
+ | local:update('existing-db', 'doc.xml', db:add#2) | ||
+ | </pre> | ||
+ | |} | ||
+ | |||
+ | ==update:for-each== | ||
+ | |||
+ | {| | ||
+ | |- valign="top" | ||
+ | | width='120' | '''Signature''' | ||
+ | |<pre>update:for-each( | ||
+ | $input as item()*, | ||
+ | $action as function(item()) as item()* | ||
+ | ) as empty-sequence()</pre> | ||
+ | |- valign="top" | ||
+ | | '''Summary''' | ||
+ | |The updating variant of [[Higher-Order Functions#fn:for-each|fn:for-each]] applies the specified updating <code>$action</code> to every item of <code>$input</code>. | ||
+ | |- valign="top" | ||
+ | | '''Examples''' | ||
+ | | | ||
+ | * Creates two databases: | ||
+ | <pre lang='xquery'> | ||
+ | let $names := ('db1', 'db2') | ||
+ | return update:for-each($names, db:create#1) | ||
+ | </pre> | ||
+ | |} | ||
+ | |||
+ | ==update:for-each-pair== | ||
+ | |||
+ | {| | ||
+ | |- valign="top" | ||
+ | | width='120' | '''Signature''' | ||
+ | |<pre>update:for-each-pair( | ||
+ | $input1 as item()*, | ||
+ | $input2 as item()*, | ||
+ | $action as function(item()) as item()* | ||
+ | ) as empty-sequence()</pre> | ||
+ | |- valign="top" | ||
+ | | '''Summary''' | ||
+ | |The updating variant of [[Higher-Order Functions#fn:for-each-pair|fn:for-each-pair]] applies the specified updating <code>$action</code> to the successive pairs of items of <code>$input1</code> and <code>$input2</code>. Evaluation is stopped if one sequence yields no more items. | ||
+ | |- valign="top" | ||
+ | | '''Examples''' | ||
+ | | | ||
+ | * Renames nodes in an XML snippets: | ||
+ | <pre lang='xquery'> | ||
+ | copy $xml := <xml><a/><b/></xml> | ||
+ | modify update:for-each-pair( | ||
+ | ('a', 'b'), | ||
+ | ('d', 'e'), | ||
+ | function($source, $target) { | ||
+ | for $e in $xml/*[name() = $source] | ||
+ | return rename node $e as $target | ||
+ | } | ||
+ | ) | ||
+ | return $xml | ||
+ | </pre> | ||
+ | |} | ||
+ | |||
+ | ==update:map-for-each== | ||
+ | |||
+ | {| width='100%' | ||
+ | | width='120' | '''Signature''' | ||
+ | |<pre>update:map-for-each( | ||
+ | $map as map(*), | ||
+ | $action as function(xs:anyAtomicType, item()*) as item()* | ||
+ | ) as item()*</pre> | ||
+ | |- valign="top" | ||
+ | | '''Summary''' | ||
+ | |The updating variant of {{Function|Map|map:for-each}} applies the specified {{Code|$action}} to every key/value pair of the supplied {{Code|$map}} and returns the results as a sequence. | ||
+ | |- valign="top" | ||
+ | | '''Examples''' | ||
+ | | | ||
+ | * Inserts attributes into a document: | ||
+ | <pre lang='xquery'> | ||
+ | copy $doc := <xml/> | ||
+ | modify update:map-for-each( | ||
+ | map { | ||
+ | 'id': 'id0', | ||
+ | 'value': 456 | ||
+ | }, | ||
+ | function($key, $value) { | ||
+ | insert node attribute { $key } { $value } into $doc | ||
+ | } | ||
+ | ) | ||
+ | return $doc</pre> | ||
+ | |} | ||
=Output= | =Output= | ||
==update:output== | ==update:output== | ||
− | |||
− | |||
{| width='100%' | {| width='100%' | ||
− | |- | + | |- valign="top" |
− | | width='120' | ''' | + | | width='120' | '''Signature''' |
− | | | + | |<pre>update:output( |
− | |- | + | $input as item()* |
+ | ) as empty-sequence()</pre> | ||
+ | |- valign="top" | ||
| '''Summary''' | | '''Summary''' | ||
− | |This function can be used to | + | |This function can be used if {{Option|MIXUPDATES}} is not enabled, and if values need to be returned within an updating expression: The supplied {{Code|$input}} will be cached and returned at the very end, i.e., after all updates on the ''pending update list'' have been processed. If one of the supplied items is affected by an update, a copy will be created and cached instead. |
− | |- | + | |- valign="top" |
| '''Examples''' | | '''Examples''' | ||
| | | | ||
Line 24: | Line 139: | ||
|} | |} | ||
− | ==update: | + | ==update:cache== |
− | |||
− | |||
{| width='100%' | {| width='100%' | ||
− | |- | + | |- valign="top" |
− | | width='120' | ''' | + | | width='120' | '''Signature''' |
− | | | + | |<pre>update:cache( |
− | |- | + | $reset as xs:boolean? := false() |
+ | ) as item()*</pre> | ||
+ | |- valign="top" | ||
| '''Summary''' | | '''Summary''' | ||
− | |Returns the items that have been cached by | + | |Returns the items that have been cached by {{Function||update:output}}. The output cache can optionally be {{Code|$reset}}. The function can be used to check which items will eventually be returned as the result of an updating function.<br/>This function is ''nondeterministic'': It will return different results before and after items have been cached. The function can be useful for writing [[Unit Module|unit tests]]. |
|} | |} | ||
=Changelog= | =Changelog= | ||
+ | |||
+ | ;Version 9.3 | ||
+ | * {{Function||update:cache}}: {{code|$reset}} parameter added. | ||
+ | |||
+ | ;Version 9.1 | ||
+ | * {{Function||update:output}}: Maps and arrays can be cached if they contain no persistent database nodes or function items. | ||
+ | |||
+ | ;Version 9.0 | ||
+ | * Updated: db:output renamed to {{Function||update:output}}, db:output-cache renamed to {{Function||update:cache}} | ||
This module was introduced with Version 9.0. | This module was introduced with Version 9.0. |
Latest revision as of 18:36, 1 December 2023
This XQuery Module provides additional functions for performing updates and returning results in updating expressions.
Contents
Conventions[edit]
All functions in this module are assigned to the http://basex.org/modules/update
namespace, which is statically bound to the update
prefix.
Except for update:output-cache
, all functions are updating and thus comply to the XQuery Update constraints.
Updates[edit]
update:apply[edit]
Signature | update:apply( $function as function(*), $arguments as array(*) ) as empty-sequence() |
Summary | The updating variant of fn:apply applies the specified updating $function to the specified $arguments .
|
Examples |
declare %updating function local:update(
$database as xs:string,
$path as xs:string,
$function as %updating function(item(), xs:string) as empty-sequence()
) as empty-sequence() {
update:apply($function, [ $database, $path ])
};
local:update('new-db', 'doc.xml', db:create#2),
local:update('existing-db', 'doc.xml', db:add#2)
|
update:for-each[edit]
Signature | update:for-each( $input as item()*, $action as function(item()) as item()* ) as empty-sequence() |
Summary | The updating variant of fn:for-each applies the specified updating $action to every item of $input .
|
Examples |
let $names := ('db1', 'db2')
return update:for-each($names, db:create#1)
|
update:for-each-pair[edit]
Signature | update:for-each-pair( $input1 as item()*, $input2 as item()*, $action as function(item()) as item()* ) as empty-sequence() |
Summary | The updating variant of fn:for-each-pair applies the specified updating $action to the successive pairs of items of $input1 and $input2 . Evaluation is stopped if one sequence yields no more items.
|
Examples |
copy $xml := <xml><a/><b/></xml>
modify update:for-each-pair(
('a', 'b'),
('d', 'e'),
function($source, $target) {
for $e in $xml/*[name() = $source]
return rename node $e as $target
}
)
return $xml
|
update:map-for-each[edit]
Signature | update:map-for-each( $map as map(*), $action as function(xs:anyAtomicType, item()*) as item()* ) as item()* |
Summary | The updating variant of map:for-each applies the specified $action to every key/value pair of the supplied $map and returns the results as a sequence.
|
Examples |
copy $doc := <xml/>
modify update:map-for-each(
map {
'id': 'id0',
'value': 456
},
function($key, $value) {
insert node attribute { $key } { $value } into $doc
}
)
return $doc
|
Output[edit]
update:output[edit]
Signature | update:output( $input as item()* ) as empty-sequence() |
Summary | This function can be used if MIXUPDATES is not enabled, and if values need to be returned within an updating expression: The supplied $input will be cached and returned at the very end, i.e., after all updates on the pending update list have been processed. If one of the supplied items is affected by an update, a copy will be created and cached instead.
|
Examples |
|
update:cache[edit]
Signature | update:cache( $reset as xs:boolean? := false() ) as item()* |
Summary | Returns the items that have been cached by update:output . The output cache can optionally be $reset . The function can be used to check which items will eventually be returned as the result of an updating function.This function is nondeterministic: It will return different results before and after items have been cached. The function can be useful for writing unit tests. |
Changelog[edit]
- Version 9.3
update:cache
:$reset
parameter added.
- Version 9.1
update:output
: Maps and arrays can be cached if they contain no persistent database nodes or function items.
- Version 9.0
- Updated: db:output renamed to
update:output
, db:output-cache renamed toupdate:cache
This module was introduced with Version 9.0.