UUIDs generated using ossp-uuid on windows not unique

Meetesh Karia <meetesh.karia@gmail.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&amp;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?

regards, tom lane

Tom Lane wrote:

Meetesh Karia <meetesh.karia@gmail.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&amp;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

Stefan Kaltenbrunner <stefan@kaltenbrunner.cc> writes:

Tom Lane wrote:

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

Oh, so that doesn't work either :-(. However, at least it's been
fixed upstream:
http://archives.postgresql.org/pgsql-bugs/2008-05/msg00070.php
http://cvs.ossp.org/pkg/lib/uuid/ChangeLog

regards, tom lane

Hi.

Sorry, late the information.....
My patch was applied after the review of Ralf-san. However, The timing of a
release was different. Then, patch is only current CVS-HEAD.
http://cvs.ossp.org/chngview?cn=6001

I thought that this problem was very important. It was sufficient reason to
apply to 8.3.3 of pginstaller. Therefore, It should return the result of a wish.

Regards,
Hiroshi Saito

----- Original Message -----
From: "Tom Lane" <tgl@sss.pgh.pa.us>

On Tue, Jun 17, 2008 at 5:21 AM, Hiroshi Saito <z-saito@guitar.ocn.ne.jp> wrote:

Hi.

Sorry, late the information.....
My patch was applied after the review of Ralf-san. However, The timing of a
release was different. Then, patch is only current CVS-HEAD.
http://cvs.ossp.org/chngview?cn=6001

I thought that this problem was very important. It was sufficient reason to
apply to 8.3.3 of pginstaller. Therefore, It should return the result of a
wish.

It's not in 8.3.3 - I'm still waiting for details of how to build it,
as it's not exactly obvious.

--
Dave Page
EnterpriseDB UK: http://www.enterprisedb.com

Hi.

Um, I will arrange information and write wiki. .
Is it a suitable place?

This is some information.
http://winpg.jp/~saito/pg_work/OSSP_win32/
uuid-ossp.dll(MinGW compile) is this.
http://winpg.jp/~saito/pg_work/OSSP_win32/pg8.3.3-win-bin-uuid-ossp.zip

Regards,
Hiroshi Saito

----- Original Message -----
From: "Dave Page" <dpage@postgresql.org>

On Tue, Jun 17, 2008 at 10:25 AM, Hiroshi Saito
<z-saito@guitar.ocn.ne.jp> wrote:

Hi.

Um, I will arrange information and write wiki. . Is it a suitable place?

A README file at http://winpg.jp/~saito/pg_work/OSSP_win32/ would be enough.

This is some information. http://winpg.jp/~saito/pg_work/OSSP_win32/
uuid-ossp.dll(MinGW compile) is this.
http://winpg.jp/~saito/pg_work/OSSP_win32/pg8.3.3-win-bin-uuid-ossp.zip

We need a VC++ .lib for the installer. When I tried last time, I
unpacked the source, replaced the headers with those in the msvc
directory, and applied your patch. The build then failed with various
missing (unix-specific) headers iirc. Do you have a set of dummy
replacements someplace in your build environment?

--
Dave Page
EnterpriseDB UK: http://www.enterprisedb.com

Hi.

Please this.
http://winpg.jp/~saito/pg_work/OSSP_win32/msvc/

P.S)
sorry,
It did not have a machine, when it mailed with you before.

Regards,
Hiroshi Saito

----- Original Message -----
From: "Dave Page" <dpage@postgresql.org>

Using the dll from the link that Hiroshi posted actually fixed v1 in my
case (though perhaps it's just an unrelated side-effect caused by using
a different random number generator which might be slower???). Thanks!

Anyhow, I would have expected v1 to work fine in this case too as the
ossp-uuid implementation has provisions for preventing overlapping ids
when they're generated in rapid succession. And, as I was only
generating about 1 uuid/ms, I didn't think that would be pushing the
limits of the algorithm.

Thanks again everyone,
Meetesh

Tom Lane wrote:

On Tue, Jun 17, 2008 at 11:17 AM, Hiroshi Saito
<z-saito@guitar.ocn.ne.jp> wrote:

Hi.

Please this.
http://winpg.jp/~saito/pg_work/OSSP_win32/msvc/

Ahh, a makefile - that makes things somewhat clearer :-)

Thanks - I've updated the build machine so future releases will
include this fix.

--
Dave Page
EnterpriseDB UK: http://www.enterprisedb.com