[MarkLogic Dev General] Unique key construction
Darin McBeath
ddmcbeath at yahoo.com
Mon Mar 29 08:35:27 PST 2010
Yes, that would likely be more efficient ... forgot that his function had been added :-)
________________________________
From: Michael Blakeley <michael.blakeley at marklogic.com>
To: General Mark Logic Developer Discussion <general at developer.marklogic.com>
Cc: "McBeath, Darin W (ELS-STL)" <D.McBeath at elsevier.com>
Sent: Mon, March 29, 2010 12:18:26 PM
Subject: Re: [MarkLogic Dev General] Unique key construction
Wouldn't it be more efficient to add xdmp:elapsed-time()?
-- Mike
On 2010-03-29 08:19, McBeath, Darin W (ELS-STL) wrote:
> I believe this could be fixed (if necessary) by wrapping the current-dateTime() call with a xdmp:eval.
>
> xdmp:eval("current-dateTime()")
>
> Darin.
>
> -----Original Message-----
> From: general-bounces at developer.marklogic.com on behalf of Geert Josten
> Sent: Mon 3/29/2010 10:00 AM
> To: General Mark Logic Developer Discussion
> Subject: RE: [MarkLogic Dev General] Unique key construction
>
> Note: this code will return only one unique value per transaction. current-datetime() returns the same value throughout the transaction as MarkLogic Server is based on point-in-time querying..
>
> Kind regards,
> Geert
>
> ________________________________
> From: general-bounces at developer.marklogic.com [mailto:general-bounces at developer.marklogic.com] On Behalf Of Keith L. Breinholt
> Sent: maandag 29 maart 2010 16:45
> To: General Mark Logic Developer Discussion
> Subject: RE: [MarkLogic Dev General] Unique key construction
>
>
> Here is a UUID version 3 implementation that we use for URLs that is unique to the name, host and time created:
>
>
>
> declare variable $g_defaultNamespace as xs:string := xdmp:host-name(xdmp:host());
> declare variable $g_uuidVersion as xs:unsignedLong := 3;
> declare variable $g_uuidReserved as xs:unsignedLong := 8;
>
> (:
> Calculate the UUID and set the UUID property on the file.
>
> The layout of a UUID is as follows.
> 0 1 2 3
> 0 1 2 3 4 5 6 7 8 9 a b c d e f 0 1 2 3 4 5 6 7 8 9 a b c d e f
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | time_low |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | time_mid | time_hi |version|
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |clk_seq_hi |res| clk_seq_low | node (0-1) |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | node (2-5) |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> 0 1 2 3 4 5 6 7 8 9 a b c d e f 0 1 2 3 4 5 6 7 8 9 a b c d e f
>
> This implements version 3 of the UUID specification.
> The timestamp is a 60-bit value.
> The clock sequence is a 14 bit value.
> The node is a 48-bit name value.
> :)
> declare function meta:uuid( $uri as xs:string )
> as xs:string
> {
> meta:uuid( $uri, $g_defaultNamespace )
> };
>
> declare function meta:uuid( $uri as xs:string, $namespace as xs:string )
> as xs:string
> {
> (: calculate md5 with a dateTime for our random values :)
> let $hash := xdmp:md5( concat( $uri, xs:string(current-dateTime()), $namespace ) )
> return
> concat (
> substring( $hash, 1, 15 ),
> (: set version bits :)
> xdmp:integer-to-hex($g_uuidVersion),
> (: set reserved bits :)
> substring( $hash, 17, 1 ),
> xdmp:integer-to-hex((xdmp:hex-to-integer(substring($hash, 18, 1)) idiv 4) + $g_uuidReserved),
> substring( $hash, 19, 14 )
> )
> };
>
>
>
>
> Keith L. Breinholt
>
> breinholtkl at ldschurch.org
>
>
>
>
>
> -----Original Message-----
> From: general-bounces at developer.marklogic.com [mailto:general-bounces at developer.marklogic.com] On Behalf Of Geert Josten
> Sent: Monday, March 29, 2010 2:35 AM
> To: General Mark Logic Developer Discussion
> Subject: RE: [MarkLogic Dev General] Unique key construction
>
>
>
> 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
>
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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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