Difference between revisions of "Job Module"
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| '''Summary''' | | '''Summary''' | ||
− | |Returns the result of | + | |Returns the cached result of a query with the specified job {{Code|$id}}: |
− | * Results can only be retrieved once. After retrieval, the cached result will be | + | * Results can only be retrieved once. After retrieval, the cached result will be dropped. |
− | * If the query raised an error, the error will be raised instead. | + | * If the query raised an error, the cached error will be raised instead. |
|- | |- | ||
| '''Errors''' | | '''Errors''' |
Revision as of 00:53, 27 June 2016
This XQuery Module provides functions for organizing running commands and queries (…more to come).
Contents
Conventions
All functions in this module are assigned to the http://basex.org/modules/jobs
namespace, which is statically bound to the jobs
prefix. Errors will be bound to the same prefix.
Functions
jobs:current
Signatures | jobs:current() as xs:string
|
Summary | Returns the id of the current query job. |
jobs:list
Signatures | jobs:list() as xs:string*
|
Summary | Returns the ids of all jobs that are either being executed asynchronously, or that are still registered because their results have been cached. |
Examples |
|
jobs:finished
Signatures | jobs:finished($id as xs:string) as xs:boolean
|
Summary | Indicates if the evaluation of a job with the specified query $id has finished. If true is returned, the job has either finished, or the query id is unknown.
|
jobs:stop
Signatures | jobs:stop($id as xs:string) as empty-sequence()
|
Summary | Cancels the execution of a job with the specified $id , or drops the cached result of a query. Unknown query ids are ignored.
|
Asynchronous Execution
Asynchronous query execution is recommendable if a client does not, or cannot, wait until a request is fully processed. This is e. g. the case with web browsers, which will usually cancel a request after a specific timeout. In such cases, you can use asynchronous execution to trigger another server-side process, which will start the time-consuming process, and fetch the result later on as soon as it is available.
jobs:eval
Signatures | jobs:eval($query as xs:string) as xs:string jobs:eval($query as xs:string, $bindings as map(*)) as xs:string jobs:eval($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 ASYNCTIMEOUT is exceeded. Queries may be updating.Variables and context items can be declared via $bindings (see xquery:eval for more details). The $options parameter contains evaluation options:
|
Errors | overflow : Too many queries or query results are queued. To fix this, the query results should be retrieved. |
Examples |
declare %rest:POST("{$query}") %rest:path('/eval') function local:eval($query) { jobs:eval($query) }; |
jobs:result
Signatures | jobs:result($id as xs:string) as item()*
|
Summary | Returns the cached result of a query with the specified job $id :
|
Errors | running : the query is still running.unknown : the supplied query id is unknown: The query result may already have been retrieved, or query execution may have been stopped. |
Examples |
declare %rest:path('/result/{$id}') function local:result($id) { jobs:result($id) };
let $query := jobs:eval('(1 to 10000000)[. = 1]') return ( hof:until( function($result) { jobs:finished($query) }, function($curr) { prof:sleep(10) }, () ), jobs:result($query) ) |
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.