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Job Functions

This module provides functions for registering new query jobs and orchestrating existing jobs. Jobs can be queries, commands, operations performed by a database client, and HTTP requests.


All functions in this module are assigned to the namespace, which is statically bound to the job prefix. Errors will be bound to the same prefix.


A job can be registered as service by supplying the service option to job:eval:

(: register job as service; will be run every day at 1 am :)
  options := { 'id':'cleanup', 'start':'01:00:00', 'interval':'P1D', 'service': true() }

(: list registered services :)
(: result: <job base-uri="..." id="cleanup" interval="P1D" start="01:00:00">db:drop("tmp")</job> :)

(: unregister job :)
job:remove('cleanup', { 'service': true() })
Some more notes:
  • All job services will be scheduled for evaluation when the BaseX server or BaseX HTTP server is started.
  • If a job service is outdated (e.g. because a supplied end time has been exceeded), it will be removed from the jobs file at startup time.
  • The job definitions are stored in a jobs.xml file in the database directory. It can also be edited manually.

Executing Jobs

There are cases in which a client does not, or cannot, wait until a request is fully processed. The client may be a browser, which sends an HTTP request to the server to start another time-consuming query job. The functions in this section allow you to register new query jobs and access existing ones. Jobs can be executed immediately (i.e., as soon as a free slot is available) or scheduled for repeated execution. Each registered job gets a job ID, and the ID can be used to retrieve a query result, stop a job, or wait for its termination.


  $query     as xs:anyAtomicType,
  $bindings  as map(*)?           := {},
  $options   as map(*)?           := {}
) as xs:string
SummarySchedules the evaluation a new query job for the supplied $query (of type xs:string, or of type xs:anyURI if points to a resource), and returns a job ID. The job will be queued until a free slot is available, and the query result can be cached. Queries can be updating, and variables and the context value can be declared via $bindings (see xquery:eval for more details). The following $options are available:
cachefalse() The result is cached in main memory until it is fetched via job:result, or until CACHETIMEOUT is exceeded. If the query raises an error, it will be cached and returned instead.
servicefalse() Additionally register the job as service. Registered services must have no variable bindings.
logfalse() Write the specified string to the database logs. Two log entries are stored, one at the beginning and another one after the execution of the job.
start An xs:dayTimeDuration, xs:time, xs:dateTime or xs:integer value can be specified to delay the execution of the query:
  • If xs:dayTimeDuration is specified, the query will be queued after the specified duration has passed. Examples of valid values are: P1D (1 day), PT5M (5 minutes), PT0.1S (100 ms). An error will be raised if a negative value is specified.
  • If xs:dateTime is specified, the query will be executed at this date. Examples for valid values are: 2018-12-31T23:59:59 (New Year’s Eve 2018, close to midnight). An error will be raised if the specified time lies in the past.
  • If xs:time is specified, the query will be executed at this time of the day. Examples of valid times are: 02:00:00 (2am local time), 12:00:00Z (noon, UTC). If the time lies in the past, the query will be executed the next day.
  • An integer will be interpreted as minutes. If the specified number is greater than the elapsed minutes of the current hour, the query will be executed one hour later.
interval An xs:dayTimeDuration value can be specified to execute the query periodically. An error is raised if the specified interval is less than one second (PT1S). If the next scheduled call is due, and if a query with the same ID is still running, it will be skipped.
end Scheduling can be stopped after a given time or duration. The string format is the same as for start. An error is raised if the resulting end time is smaller than the start time.
base-uri The base-uri property for the query. This URI will be used when resolving relative URIs, such as with fn:doc.
id A custom job ID. The ID must not start with the standard job prefix, and it can only be assigned if no job with the same name exists.
idThe specified ID is invalid or has already been assigned.
optionsThe specified options are conflicting.
overflowToo many queries or query results are queued.
rangeA specified time or duration is out of range.
job:eval("1 + 3", (), { 'cache': true() })
Cache query result. The returned ID can be used to pick up the result with job:result.
  "import module namespace mail='mail'; mail:send('Happy birthday!')",
  { 'start': '2018-09-01T06:00:00' }
A happy birthday mail will be sent at the given date.
function local:start($query) {
  job:eval($query, (), { 'start': '02:00:00', 'interval': 'P1D' })

function local:stop($id) {
The following RESTXQ functions can be called to execute a query at 2 am every day. An ID will be returned by the first function, which can be used to stop the scheduler via the second function.
job:eval("prof:sleep(1500)", (), { 'interval': 'PT1S', 'end': 'PT10S' })
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.
The query in the specified file will be evaluated once.
job:eval(static-base-uri(), {}, { 'start': 'PT5S' })
The following expression, if stored in a file, will be evaluated every 5 seconds.


  $id       as xs:string,
  $options  as map(*)?    := {}
) as item()*
SummaryReturns the cached result of a job with the specified job $id:
  • If the original job has raised an error, the cached error will be raised instead.
  • The cached result or error will be dropped after it has been retrieved.
  • If the result has not been cached or if it has been dropped, an empty sequence is returned.

The following $options are available:

keepfalse() Keep the cached result or error after retrieval.
function local:result($id) {
The following RESTXQ function will either return the result of a previously started job or raise an error.
let $query := job:eval('(1 to 10000000)[. = 1]', options := { 'cache': true() })
return (
The following query demonstrates how the results of an executed query can be returned within the same query (see below why you should avoid this pattern in practice). Note that queries of this kind can cause deadlocks! If the original query and the new query perform updates on the same database, the second query will only be run after the first one has been executed, and the first query will wait for the second query forever. You should resort to xquery:fork-join if you want to have full control on parallel query execution.


  $id       as xs:string,
  $options  as map(*)?    := {}
) as empty-sequence()
SummaryTriggers the cancelation of a job with the specified $id, cancels a scheduled job or removes a cached result. Unknown IDs are ignored. All jobs are gracefully stopped; it is up to the process to decide when it is safe to shut down. The following $options are available:
servicefalse() Additionally remove the job from the job services list.
job:list()[. != job:current()] ! job:remove(.)
Stops and discards all jobs except for the current one.
Interrupts the current job.


  $id  as xs:string
) as empty-sequence()
SummaryWaits for the completion of a job with the specified $id:
  • The function will terminate immediately if the job ID is unknown. This is the case if a future job has not been queued yet, or if the ID has already been discarded after job evaluation.
  • If the function is called with the ID of a queued job, or repeatedly executed job, it may stall and never terminate.
selfThe current job cannot be addressed.

Listing Jobs


job:current() as xs:string
SummaryReturns the ID of the current job.


job:list() as xs:string*
SummaryReturns the IDs of all jobs that are currently registered. The list includes scheduled, queued, running, stopped, and finished jobs with cached results.
Returns the same job ID as job:current if no other job is registered.


  $id  as xs:string  := ()
) as element(job)*
SummaryReturns information on all jobs that are currently registered, or on a job with the specified $id (or an empty sequence if this job is not found). The list includes scheduled, queued, running jobs, and cached jobs. A string representation of the job, or its URI, will be returned as a value. The returned elements have additional attributes:
  • id: job ID
  • type: type of the job (command, query, REST, RESTXQ, etc.)
  • state: current state of the job: scheduled, queued, running, cached
  • user: user who started the job
  • duration: evaluation time (included if a job is running or if the result was cached)
  • start: next start of job (included if a job will be executed repeatedly)
  • time: time when job was registered


  $id  as xs:string
) as map(*)
SummaryReturns the variable bindings of an existing job with the specified $id. If no variables have been bound to this job, an empty map is returned.


  $id  as xs:string
) as xs:boolean
SummaryIndicates if the evaluation of an already running job with the specified $id has finished. As the IDs of finished jobs will usually be discarded, unless caching is enabled, the function will also return true for unknown jobs.
  • false indicates that the job ID is scheduled, queued, or currently running.
  • true 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).


job:services() as element(job)*
SummaryReturns a list of all jobs that have been persistently registered as Services.


idThe specified ID is invalid or has already been assigned.
optionsThe specified options are conflicting.
overflowToo many queries or query results are queued.
rangeA specified time or duration is out of range.
runningA query is still running.
selfThe current job cannot be addressed.
serviceRegistered services cannot be parsed, added or removed.


Version 10.0
  • Added: job:bindings
  • Updated: Renamed from Jobs Module to Job Module. The namespace URI has been updated as well.
  • Updated: job:remove renamed from jobs:stop.
  • Updated: job:result: options argument added.
Version 9.7
  • Updated: job:result: return empty sequence if no result is cached.
Version 9.5
  • Updated: job:eval: integers added as valid start and end times.
Version 9.4Version 9.2
  • Deleted: job:invoke (merged with job:eval)
Version 9.1Version 9.0Version 8.6Version 8.5
  • Added: New module added.

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