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hof:until( function($f) { jobs:finishedwait($query) }, function($f) { prof:sleep(10) }, () ),
→jobs:wait
|-
| '''Summary'''
|Indicates if the evaluation of a an already running job with the specified {{Code|$id}} has finished. As the ids of finished jobs will usually be discarded, unless caching is enabled, the function will also return <code>true</code> for unknown jobs.
* <code>false</code> indicates that the job id is scheduled, queued, or currently running.
* <code>true</code> will be returned if the job has either finished, or if the id is unknown (because the ids of all finished jobs will not be cached).
|-
| '''Summary'''
|Cancels Triggeres the execution cancelation of a job with the specified {{Code|$id}}, drops the cached result of a query, or cancels a scheduled job. Unknown ids are ignored. All jobs are gracefully stopped; it is up to the process to decide when it is safe to shut down.|} ==jobs:wait== {| width='100%'|-| width='120' | '''Signatures'''|{{Func|jobs:wait|$id as xs:string|empty-sequence()}}|-| '''Summary'''|Waits for the completion of a job with the specified {{Code|$id}}. If the function is called with the id of a queued job, or repeatedly executed job, it may stall and never terminate.|-| '''Errors'''|{{Error|self|#Errors}} if the current job is addressed.<br/>
|}
Asynchronous query execution is recommendable if a client does not, or cannot, wait until a request is fully processed. This is e. g. the case with web browsers, which will usually cancel a request after a specific timeout. In such cases, you can use asynchronous execution to trigger another server-side process, which will start the time-consuming process, and fetch the result later on as soon as it is available.
==jobs:scheduleeval== {{Mark|Updated with Version 8.6}}: <code>id</code> option added.
{| width='100%'
|-
| width='120' | '''Signatures'''
|{{Func|jobs:scheduleeval|$query as xs:string|xs:string}}<br />{{Func|jobs:scheduleeval|$query as xs:string, $bindings as map(*)?|xs:string}}<br />{{Func|jobs:scheduleeval|$query as xs:string, $bindings as map(*)?, $options as map(xs:string, xs:string)|xs:string}}<br />
|-
| '''Summary'''
|Schedules the execution evaluation of the supplied {{Code|$query}} and returns a query id. The query will be queued, and the result will optionally be cached. Queries may can be updating. Variables and context items can be declared via {{Code|$bindings}} (see [[XQuery Module#xquery:eval|xquery:eval]] for more details). The {{Code|$options}} parameter contains scheduling options:
* {{Code|cache}}: indicates if the query result will be cached or ignored (default: <code>false</code>):
** The result will be cached in main-memory until it is fetched via [[#jobs:result|jobs:result]], or until {{Option|CACHETIMEOUT}} is exceeded.
** If a dateTime is specified, the query will be executed at this date. Examples for valid values are: <code>2018-12-31T23:59:59</code> (New Year's Eve 2018, close to midnight). An error will be raised if the specified time lies in the past.
* {{Code|interval}}: a dayTimeDuration string can be specified to execute the query periodically. An error is raised if the specified interval is less than one second (<code>PT1S</code>). If the next scheduled call is due, and if a query with the same id is still running, it will be skipped.
* {{Code|end}}: scheduling can be stopped after a given time or duration. The string format is the same as for {{Code|start}}. An error is raised if the resulting end time is smaller than the start time.* {{Code|base-uri}}: set sets the [https://www.w3.org/TR/xquery-31/#dt-static-base-uri base-uri property] for the query. This URI will be used when resolving relative URIs, such as with {{Code|fn:doc}}.* {{Code|id}}: sets a custom job id. The id must not start with the standard <code>job</code> prefix, and it can only be assigned if no job with the same name exists.
|-
| '''Errors'''
|{{Error|overflow|#Errors}} Query execution is rejected, because too many jobs are queued or being executed. {{Option|CACHETIMEOUT}} can be decreased if the default setting is too restrictive.<br/>{{Error|range|#Errors}} A specified time or duration is out of range.<br/>{{Error|id|#Errors}} The specified id is invalid or has already been assigned.
|-
| '''Examples'''
* Cache query result. The returned id can be used to pick up the result with [[#jobs:result|jobs:result]]:
<pre class='brush:xquery'>
jobs:scheduleeval("1+3", (), map { 'cache': true() })
</pre>
* A happy birthday mail will be sent at the given date:
<pre class="brush:xquery">
jobs:scheduleeval("import module namespace mail='mail'; mail:send('Happy birthday!')",
(), map { 'start': '2018-09-01T06:00:00' })}}
</pre>
<pre class='brush:xquery'>
declare %rest:POST("{$query}") %rest:path('/start-scheduling') function local:start($query) {
jobs:scheduleeval($query, (), map { 'start': '02:00:00', 'interval': 'P1D' })
};
declare %rest:path('/stop-scheduling/{$id}') function local:stop($id) {
};
</pre>
* Query execution is scheduled for every second, and for 10 seconds in total. As the query itself will take 1.5 seconds, it will only be executed every second time:
<pre class="brush:xquery">
jobs:scheduleeval("prof:sleep(1500)", (), map { 'interval': 'PT1S', 'end': 'PT10S' })
</pre>
|}
|-
| '''Summary'''
|Returns the cached result of a query job with the specified job {{Code|$id}}:
* Results can only be retrieved once. After retrieval, the cached result will be dropped.
* If the original query job has raised an error, the cached error will be raised instead.
|-
| '''Errors'''
| '''Examples'''
|
* The following [[RESTXQ]] function will either return the result of a previously started query job or raise an error:
<pre class='brush:xquery'>
declare %rest:path('/result/{$id}') function local:result($id) {
};
</pre>
* The following query demonstrates how the results of an asynchronously executed query can be returned within the same query. Please remember that this is not the common way how these functions will be used in practice:
<pre class='brush:xquery'>
let $query := jobs:scheduleeval('(1 to 10000000)[. = 1]', map{}, map{ 'cache': true() })
return (
jobs:result($query)
)
</pre>
Please note that this query can easily cause a deadlock if the asynchronously executed query will be queued. In practice. In practice, you should avoid this pattern and resort to [[XQuery Module#xquery:fork-join|xquery:fork-join]] if you want to do things in parallel.
|}
| Too many queries or query results are queued.
|-
|{{Code|range}}
| A specified time or duration is out of range.
|-
|{{Code|id}}
| The specified is invalid or has already been assigned.
|-
|{{Code|self}}
| The current job cannot be addressed.
|}
=Changelog=
;Version 8.6
* Updated: [[#jobs:eval|jobs:eval]]: <code>id</code> option added.
The module was introduced with Version 8.5.
