Update Module

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This [[Module Library|XQuery Module]] adds updating functions.
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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 [[#update:output-cache|update:output-cache]], all functions are ''updating'' and thus comply to the XQuery Update constraints.
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 +
=Updates=
 +
 +
==update:apply==
 +
 +
{|
 +
|-
 +
| width='120' | '''Signatures'''
 +
|{{Func|update:apply|$function as function(*), $arguments as array(*)|empty-sequence()}}
 +
|-
 +
| '''Summary'''
 +
|The updating variant of [[XQuery 3.1#fn:apply|fn:apply]] applies the specified updating <code>$function</code> to the specified <code>$arguments</code>.
 +
|-
 +
| '''Examples'''
 +
|
 +
* Creates a new database with an initial document and adds a document to an existing database.
 +
<pre class="brush: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, $path ])
 +
};
 +
local:update('new-db', 'doc.xml', db:create#2),
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local:update('existing-db', 'doc.xml', db:add#2)
 +
</pre>
 +
|}
 +
 +
==update:for-each==
 +
 +
{|
 +
|-
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| width='120' | '''Signatures'''
 +
|{{Func|update:for-each|$seq as item()*, $function as function(item()) as item()*|empty-sequence()}}
 +
|-
 +
| '''Summary'''
 +
|The updating variant of [[Higher-Order Functions#fn:for-each|fn:for-each]] applies the specified updating <code>$function</code> to every item of <code>$seq</code>.
 +
|-
 +
| '''Examples'''
 +
|
 +
* Creates two databases:
 +
<pre class="brush:xquery">
 +
let $names := ('db1', 'db2')
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return update:for-each($names, db:create#1)
 +
</pre>
 +
|}
 +
 +
==update:for-each-pair==
 +
 +
{|
 +
|-
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| width='120' | '''Signatures'''
 +
|{{Func|update:for-each-pair|$seq1 as item()*, $function as function(item()) as item()*|empty-sequence()}}
 +
|-
 +
| '''Summary'''
 +
|The updating variant of [[Higher-Order Functions#fn:for-each-pair|fn:for-each-pair]] applies the specified updating <code>$function</code> to the successive pairs of items of <code>$seq1</code> and <code>$seq2</code>. 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:
 +
<pre class="brush:xquery">
 +
copy $xml := <xml><a/><b/></xml>
 +
modify update:for-each-pair(
 +
  ('a', 'b'),
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  ('d', 'e'),
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  function($source, $target) {
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    for $e in $xml/*[name() = $source]
 +
    return rename node $e as $target
 +
  }
 +
)
 +
return $xml
 +
</pre>
 +
|}
 +
 +
==update:map-for-each==
 +
 +
{| width='100%'
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| width='120' | '''Signatures'''
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|{{Func|update:map-for-each|$map as map(*), $function as function(xs:anyAtomicType, item()*) as item()*|item()*}}
 +
|-
 +
| '''Summary'''
 +
|The updating variant of {{Function|Map|map:for-each}} applies the specified {{Code|$function}} to every key/value pair of the supplied {{Code|$map}} and returns the results as a sequence.
 +
|-
 +
| '''Examples'''
 +
|
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* Inserts attributes into a document:
 +
<pre class="brush: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==
-
 
-
{{Mark|Updated with Version 9.0}}: formerly {{Code|db:output}}.
 
{| width='100%'
{| width='100%'
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|-
|-
| '''Summary'''
| '''Summary'''
-
|This function can be used to both perform updates and return results in a single query. 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. As nodes may be updated, they will be copied before being cached.<br/>The function can only be used together with [[XQuery Update#Updating Expressions|updating expressions]]; if the function is called within a transform expression, its results will be discarded.
+
|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.
|-
|-
| '''Examples'''
| '''Examples'''
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|}
|}
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==update:output-cache==
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==update:cache==
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+
-
{{Mark|Updated with Version 9.0}}: formerly {{Code|db:output-cache}}.
+
{| width='100%'
{| width='100%'
|-
|-
| width='120' | '''Signatures'''
| width='120' | '''Signatures'''
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|{{Func|update:output-cache||item()*}}
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|{{Func|update:cache||item()*}}
|-
|-
| '''Summary'''
| '''Summary'''
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=Changelog=
=Changelog=
 +
 +
;Version 9.1
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 +
* [[#update:output|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|update:output}}, db:output-cache renamed to {{Function|Update|update:cache}}
This module was introduced with Version 9.0.
This module was introduced with Version 9.0.

Revision as of 12:40, 16 April 2019

This XQuery Module provides additional functions for performing updates and returning results in updating expressions.

Contents

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()
Summary The updating variant of fn:apply applies the specified updating $function to the specified $arguments.
Examples
  • 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 update:for-each($seq as item()*, $function as function(item()) as item()*) as empty-sequence()
Summary The updating variant of fn:for-each applies the specified updating $function to every item of $seq.
Examples
  • Creates two databases:
let $names := ('db1', 'db2')
return update:for-each($names, db:create#1)

update:for-each-pair

Signatures update:for-each-pair($seq1 as item()*, $function as function(item()) as item()*) as empty-sequence()
Summary 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.
Examples
  • 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()*
Summary 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.
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

Signatures update:output($result as item()*) as empty-sequence()
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.
Examples
  • update:output("Prices have been deleted."), delete node //price deletes all price elements in a database and returns an info message.

update:cache

Signatures update:cache() as item()*
Summary 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.

Changelog

Version 9.1
Version 9.0

This module was introduced with Version 9.0.

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