Difference between revisions of "Job Module"
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| '''Summary''' | | '''Summary''' | ||
− | |Prepares the supplied {{Code|$query}} string for asynchronous execution and returns a query id. The query will be queued as described in the article on [[Transaction Management]], and the result will be cached in main-memory until it is fetched via [[#jobs:result|jobs:result]], or until {{Option| | + | |Prepares the supplied {{Code|$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|jobs:result]], or until {{Option|CACHETIMEOUT}} is exceeded. Queries may be updating.<br/>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 evaluation options: |
* {{Code|cache}}: indicates if the query result will be cached or ignored (default: <code>true</code>). If the query result will not be cached, the query id will immediately be discarded after query execution, too. | * {{Code|cache}}: indicates if the query result will be cached or ignored (default: <code>true</code>). If the query result will not be cached, the query id will immediately be discarded after query execution, too. | ||
* {{Code|base-uri}}: set [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 by functions such as {{Code|fn:doc}} (default: ''empty string''). | * {{Code|base-uri}}: set [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 by functions such as {{Code|fn:doc}} (default: ''empty string''). |
Revision as of 05:06, 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 currently queued or executed. |
Examples |
|
jobs:finished
Signatures | jobs:finished($id as xs:string) as xs:boolean
|
Summary | Indicates if the evaluation of a job with the specified job $id has finished:
|
jobs:stop
Signatures | jobs:stop($id as xs:string) as empty-sequence()
|
Summary | Cancels the execution of a job with the specified $id , or drops the cached result of a query. Unknown ids are ignored.
|
Asynchronous Execution
Asynchronous query execution is recommendable if a client does not, or cannot, wait until a request is fully processed. This is e. g. the case with web browsers, which will usually cancel a request after a specific timeout. In such cases, you can use asynchronous execution to trigger another server-side process, which will start the time-consuming process, and fetch the result later on as soon as it is available.
jobs:eval
Signatures | jobs:eval($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 CACHETIMEOUT is exceeded. Queries may be updating.Variables and context items can be declared via $bindings (see xquery:eval for more details). The $options parameter contains evaluation options:
|
Errors | overflow : Too many queries or query results are queued. To fix this, the query results should be retrieved. |
Examples |
declare %rest:POST("{$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.