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|
Line 48: |
Line 48: |
| * <code>jobs:list-details()</code> returns information on the currently running job and possibly others: | | * <code>jobs:list-details()</code> returns information on the currently running job and possibly others: |
| <pre class="brush:xml"> | | <pre class="brush:xml"> |
− | <job id="job1" type="XQuery" duration="PT0S" state="running" user="admin">XQUERY jobs:list-details()</job> | + | <job id="job1" type="XQuery" duration="PT0S" state="running" user="admin"> |
| + | XQUERY jobs:list-details()</job> |
| </pre> | | </pre> |
| |} | | |} |
Revision as of 20:40, 29 June 2016
This XQuery Module provides functions for organizing running commands and queries (…more to come).
Conventions
All functions in this module are assigned to the http://basex.org/modules/jobs
namespace, which is statically bound to the jobs
prefix. Errors will be bound to the same prefix.
Functions
jobs:current
Signatures
|
jobs:current() as xs:string
|
Summary
|
Returns the id of the current job.
|
jobs:list
Signatures
|
jobs:list() as xs:string*
|
Summary
|
Returns the ids of all jobs that are currently queued or executed.
|
Examples
|
jobs:list() returns the same job id as jobs:current if no other job is running.
jobs:list()[. != jobs:current()] ! jobs:stop(.) stops and invalidates all asynchronous queries and results except for the current one.
|
jobs:list-details
Signatures
|
jobs:list-details() as element(job)*
jobs:list-details($id as xs:string) as element(job)*
|
Summary
|
Returns information on all jobs that are currently queued or executed.
|
Examples
|
jobs:list-details() returns information on the currently running job and possibly others:
<job id="job1" type="XQuery" duration="PT0S" state="running" user="admin">
XQUERY jobs:list-details()</job>
|
jobs:finished
Signatures
|
jobs:finished($id as xs:string) as xs:boolean
|
Summary
|
Indicates if the evaluation of a job with the specified $id has finished:
true indicates that the job has either finished, or that the id is unknown.
false indicates that the job id is still queued or currently running.
|
jobs:stop
Signatures
|
jobs:stop($id as xs:string) as empty-sequence()
|
Summary
|
Cancels the execution of a job with the specified $id , or drops the cached result of a query. Unknown ids are ignored. All jobs are gracefully stopped; it is up to the process to decide when it is safe to shut down.
|
Asynchronous Execution
Asynchronous query execution is recommendable if a client does not, or cannot, wait until a request is fully processed. This is e. g. the case with web browsers, which will usually cancel a request after a specific timeout. In such cases, you can use asynchronous execution to trigger another server-side process, which will start the time-consuming process, and fetch the result later on as soon as it is available.
jobs:schedule
Signatures
|
jobs:schedule($query as xs:string) as xs:string
jobs:schedule($query as xs:string, $bindings as map(*)) as xs:string
jobs:schedule($query as xs:string, $bindings as map(*), $options as map(xs:string, xs:string)) as xs:string
|
Summary
|
Prepares the supplied $query string for asynchronous execution and returns a query id. The query will be queued as described in the article on Transaction Management, and the result will be cached in main-memory until it is fetched via jobs:result, or until CACHETIMEOUT is exceeded. Queries may be updating. Variables and context items can be declared via $bindings (see xquery:eval for more details). The $options parameter contains evaluation options:
cache : indicates if the query result will be cached or ignored (default: true ). If the query result will not be cached, the query id will immediately be discarded after query execution, too.
base-uri : set base-uri property for the query. This URI will be used when resolving relative URIs by functions such as fn:doc (default: empty string).
|
Errors
|
overflow : Too many queries or query results are queued. CACHETIMEOUT can be decreased if the default setting is too restrictive.
|
Examples
|
jobs:schedule("1+3", map{}, map{ 'cache': true() }) returns a query id, e.g. Job-123 . The result can be retrieved via a second query in the same BaseX context: jobs:result("Job-123")
- The following RESTXQ function will return the id of the query thread, which evaluates the query that has been specified in the body of a POST request:
declare %rest:POST("{$query}") %rest:path('/eval') function local:schedule($query) {
jobs:schedule($query)
};
|
jobs:result
Signatures
|
jobs:result($id as xs:string) as item()*
|
Summary
|
Returns the cached result of a query with the specified job $id :
- Results can only be retrieved once. After retrieval, the cached result will be dropped.
- If the query raised an error, the cached error will be raised instead.
|
Errors
|
running : the query is still running.
unknown : the supplied query id is unknown: The query result may already have been retrieved, or query execution may have been stopped.
|
Examples
|
- The following RESTXQ function will either return the result of a previously started query or an error:
declare %rest:path('/result/{$id}') function local:result($id) {
jobs:result($id)
};
- The following query demonstrates how the results of an asynchronously executed query can be returned in a single query. Please remember that this is not the common way how these functions are used in practice:
let $query := jobs:schedule('(1 to 10000000)[. = 1]')
return (
hof:until(
function($result) { jobs:finished($query) },
function($curr) { prof:sleep(10) },
()
),
jobs:result($query)
)
|
jobs:results
Signatures
|
jobs:results() as xs:string*
|
Summary
|
Returns the ids of all jobs for which results are cached.
|
Errors
Code
|
Description
|
unknown
|
The supplied query id is unknown or not available anymore.
|
running
|
A query is still running.
|
overflow
|
Too many queries or query results are queued.
|
Changelog
The module was introduced with Version 8.5.