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==xquery:fork-join==
{{Mark|Introduced with Version 8.5}}:
{| width='100%'
|-
| width='120' | '''Signatures'''
|{{Func|xquery:fork-join|$functions as function(*)*|item()*}}
|-
|'''Summary'''
|This function executes the supplied (non-updating) functions in parallel.<br/>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 accessing a database), your single-threaded query will usually be faster, because parallelized access to disk data will often lead to randomized access patterns, which can hardly be optimized by your HD or SSD.
|-
| '''Examples'''
|
* The following function sleeps in parallel; it will be finished in 1 second if your system has at least 2 cores:
<pre class='brush:xquery'>
let $f := function() { prof:sleep(1000) }
return xquery:fork-join(($f, $f))
</pre>
* In the following query, up to four URLs will be requested in parallel:
<pre class='brush:xquery'>
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)
</pre>
|-
|'''Errors'''
|{{Error|BXXQ0006|#Errors}} an unexpected error occurred.
no edit summary
| '''Errors'''
|{{Error|BXXQ0002|#Errors}} the query contains no [[XQuery Update#Updating Expressions|updating expressions]].<br/>{{Error|BXXQ0003|#Errors}} insufficient permissions for evaluating the query.<br/>{{Error|BXXQ0004|#Errors}} query execution exceeded timeout or memory limit.<br/>{{Error|BXXQ0005|#Errors}} nested query evaluation is not allowed.<br/>Any other error that may occur while evaluating the query.
|}
| '''Errors'''
|{{Error|BXXQ0001|#Errors}} the expression contains [[XQuery Update#Updating Expressions|updating expressions]].<br/>{{Error|BXXQ0003|#Errors}} insufficient permissions for evaluating the query.<br/>{{Error|BXXQ0004|#Errors}} query execution exceeded timeout.<br/>{{Error|BXXQ0005|#Errors}} nested query evaluation is not allowed.<br/>Any other error that may occur while evaluating 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 accessing a database), your single-threaded query will usually be faster, because parallelized access to disk data will often lead to randomized access patterns, which can hardly be optimized by your HD or SSD.
==xquery:fork-join==
{{Mark|Introduced with Version 8.5}}:
{| width='100%'
|-
| width='120' | '''Signatures'''
|{{Func|xquery:fork-join|$functions as function(*)*|item()*}}
|-
|'''Summary'''
|This function executes the supplied (non-updating) functions in parallel.
|-
| '''Examples'''
|
* The following function sleeps in parallel; it will be finished in 1 second if your system has at least 2 cores:
<pre class='brush:xquery'>
let $f := function() { prof:sleep(1000) }
return xquery:fork-join(($f, $f))
</pre>
* In the following query, up to four URLs will be requested in parallel:
<pre class='brush:xquery'>
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)
</pre>
|-
|'''Errors'''
|{{Error|BXXQ0006|#Errors}} an unexpected error occurred.
|}
