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Re: UUIDs generated using ossp-uuid on windows not unique

From: Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: meetesh(dot)karia(at)alumni(dot)duke(dot)edu, pgsql-bugs(at)postgresql(dot)org
Subject: Re: UUIDs generated using ossp-uuid on windows not unique
Date: 2008-06-16 20:01:57
Message-ID: 4856C6B5.2030303@kaltenbrunner.cc (view raw or flat)
Thread:
Lists: pgsql-bugs
Tom Lane wrote:
> Meetesh Karia <meetesh(dot)karia(at)gmail(dot)com> writes:
>> As best as I can tell, the problem is caused because generation of v1 
>> UUIDs uses GetSystemTimeAsFileTime which is stated to have a resolution 
>> of 100 nanoseconds but in practice has a resolution of around 15ms 
>> (http://www.ddj.com/showArticle.jhtml?documentID=win0305a&pgno=17).
> 
> Well, any real-time clock reading is going to have finite resolution.
> If your app is expecting that version-1 UUIDs generated in rapid
> succession will be distinct, I think your app is broken.  It's just
> a little more obvious on Windows :-(.
> 
> Perhaps the v4 generation method would work better for you?

actually this has been reported before and seems to be an issue in the 
windows port of the ossp-uuid library:


http://archives.postgresql.org/pgsql-bugs/2008-05/msg00059.php


Stefan

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