[MarkLogic Dev General] Unique key construction

[Geert Josten]

Hi Deepak,

Look in the Modules, not the Admin folder. Here is a typical case taken from triggers.xqy:

define function
get-unique-trigger-id()
as xs:unsignedLong
{
  let $col := triggers-collection(),
      $attempt := xdmp:random(),
      $doc-uri := fn:concat(triggers-uri(), xs:string($attempt)),
      $docs := for $d in fn:collection($col) return fn:base-uri($d)
  return
   if ($doc-uri = $docs)
   then get-unique-trigger-id()
   else $attempt
}

You can make it slightly more robust by counting the attempts and throwing an error if you need to many attempts. The number of unique numbers generated by xdmp:random is large though, so that is only necessary when you have good reason to believe that you could approach that limit..

Kind regards,
Geert

>


drs. G.P.H. (Geert) Josten
Consultant


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> From: general-bounces at developer.marklogic.com
> [mailto:general-bounces at developer.marklogic.com] On Behalf Of
> deepak mohan
> Sent: zondag 28 maart 2010 17:44
> To: general at developer.marklogic.com
> Subject: [MarkLogic Dev General] Unique key construction
>
> Hi All,
>
> Please tell me how ML constructs the unique ID while creating
> any ML entities(App Servers, DB, forest etc.). I need to
> generate a unique ID. I tried dig into the ML Admin modules
> APi, I couldnot find the algo. Are they using random() and
> check for existence?
>
> Thanks,
> Deepak Mohanakrishnan.
>
>
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