This XQuery Module provides additional functions for performing updates and returning results in updating expressions.
Conventions
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
update:apply
Signatures
|
update:apply($function as function(*), $arguments as array(*))) as empty-sequence()
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Summary
|
The updating variant of fn:apply applies the specified updating $function to the specified $arguments .
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Examples
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- Creates a new database with an initial document and adds a document to an existing database.
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, $path ])
};
local:update('new-db', 'doc.xml', db:create#2),
local:update('existing-db', 'doc.xml', db:add#2)
|
update:for-each
Signatures
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update:for-each($seq as item()*, $function as function(item()) as item()*)) as empty-sequence()
|
Summary
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The updating variant of fn:for-each applies the specified updating $function to every item of $seq .
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Examples
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let $names := ('db1', 'db2')
return update:for-each($names, db:create#1)
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update:for-each-pair
Signatures
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update:for-each-pair($seq1 as item()*, $function as function(item()) as item()*)) as empty-sequence()
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Summary
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The updating variant of fn:for-each-pair applies the specified updating $function to the successive pairs of items of $seq1 and $seq2 . Evaluation is stopped if one sequence yields no more items.
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Examples
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- Renames nodes in an XML snippets:
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 $xml
|
update:map-for-each
Signatures
|
update:map-for-each($map as map(*), $function as function(xs:anyAtomicType, item()*) as item()*) as item()*
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Summary
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The updating variant of map:for-each applies the specified $function to every key/value pair of the supplied $map and returns the results as a sequence.
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Examples
|
- Inserts attributes into a document:
copy $doc := <xml/>
modify update:map-for-each(
map {
'id': 'id0',
'value': 456
},
function($key, $value) {
insert node attribute { $key } { $value } into $doc
}
)
return $doc
|
Output
update:output
Template:Mark: Maps and arrays can be cached if they contain no persistent database nodes or function items.
Signatures
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update:output($result as item()*) as empty-sequence()
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Summary
|
This function is a helper function for returning results in an updating expression. The argument of the function will be evaluated, and the resulting items will be cached and returned after the updates on the pending update list have been processed. If the supplied item will be affected by an update, a copy will be created and cached instead.
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Examples
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update:output("Prices have been deleted."), delete node //price deletes all price elements in a database and returns an info message.
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update:output-cache
Signatures
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update:output-cache() as item()*
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Summary
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Returns the items that have been cached by update:output. It can be used to check which items will eventually be returned as result of an updating function. This function is non-deterministic: It will return different results before and after items have been cached. It is e. g. useful when writing unit tests.
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Changelog
- Version 9.1
- update:output: Maps and arrays can be cached if they contain no persistent database nodes or function items.
This module was introduced with Version 9.0.