Re: [Zope-dev] Globally unique id's in Zope in a new way
"James W. Howe" <jwh@allencreek.com> wrote:
At 07:49 PM 3/8/00 -0500, Jason Spisak wrote:
Zopsters,
I use the Catalog for quite a bit of jumping around the ZODB, and have a 30,000 plus objects in a system. I like the idea of not having to worry about id's conflicting with other numbers that might appear (invoice numbers, employee numbers, etc...) so I don't like to use a counter for ids. [...]
I have the same problem. I want to automatically create objects and I'm currently using the time method. When I bulk add objects, I would get a collision on the time value, so I simply remembered the last id and added 1 to that value. It works for my current needs, but I wish Zope provided a standard mechanism for generating unique id's.
For example, it would actually be nice if Zope provided an implementation of UUID (called GUID by Microsoft). A UUID is a guaranteed unique 64-bit value. It's used in COM, CORBA and other systems which need to have automatically generated guaranteed unique values. The nice thing about UUID's is that they are guaranteed to be unique network wide. In other words, you (supposedly) can't generate a UUID which would ever conflict with a UUID that I generated. It does this by an algorithm which takes into account things like time-of-date, network card address, etc. I don't have the details on the algorithm but I know it is publically available. It would probably best be implemented at the C level.
Just an idea.
On Win32, this is trivial in Python:: import pywintypes guid = pywintypes.CreateGuid() return str( guid ) I *think* DCE RPC has a cognate function, uuid_create(), but I don't have documentation for it (Sun RPC probably has a similar call). Hmmm, a search of the Vaults of Parnassus (http://www.vex.net/parnassus) doesn't show any existing wrapper for either major flavor of RPC. Tres. -- ========================================================= Tres Seaver tseaver@palladion.com 713-523-6582 Palladion Software http://www.palladion.com
I thought the GUID was a 128bit number. Its not _guaranteed_ to be unique, it just has a very very high probability of being unique. You can create a globally unique number by combining the 64 bit OID for the object with a 64 bit random number (possibly from the network card address or somesuch) that is generated once for each zope installation. The 64bit OID is available as object._p_oid, and should be unique within a ZODB for the lifespan of that ZODB. Theres also a 64bit serial number (which i believe is a timestamp) available as object._p_serial Reading from these values is probably fine, but writing to them might not be a good idea.
-----Original Message----- From: zope-dev-admin@zope.org [mailto:zope-dev-admin@zope.org]On Behalf Of Tres Seaver Sent: Thursday, March 09, 2000 12:34 PM To: James W. Howe Cc: zope-dev@zope.org; Jason Spisak Subject: Re: [Zope-dev] Globally unique id's in Zope in a new way
"James W. Howe" <jwh@allencreek.com> wrote:
At 07:49 PM 3/8/00 -0500, Jason Spisak wrote:
Zopsters,
I use the Catalog for quite a bit of jumping around the ZODB,
and have a
30,000 plus objects in a system. I like the idea of not having to worry about id's conflicting with other numbers that might appear (invoice numbers, employee numbers, etc...) so I don't like to use a counter for ids. [...]
I have the same problem. I want to automatically create objects and I'm currently using the time method. When I bulk add objects, I would get a collision on the time value, so I simply remembered the last id and added 1 to that value. It works for my current needs, but I wish Zope provided a standard mechanism for generating unique id's.
For example, it would actually be nice if Zope provided an implementation of UUID (called GUID by Microsoft). A UUID is a guaranteed unique 64-bit value. It's used in COM, CORBA and other systems which need to have automatically generated guaranteed unique values. The nice thing about UUID's is that they are guaranteed to be unique network wide. In other words, you (supposedly) can't generate a UUID which would ever conflict with a UUID that I generated. It does this by an algorithm which takes into account things like time-of-date, network card address, etc. I don't have the details on the algorithm but I know it is publically available. It would probably best be implemented at the C level.
Just an idea.
On Win32, this is trivial in Python::
import pywintypes guid = pywintypes.CreateGuid() return str( guid )
I *think* DCE RPC has a cognate function, uuid_create(), but I don't have documentation for it (Sun RPC probably has a similar call). Hmmm, a search of the Vaults of Parnassus (http://www.vex.net/parnassus) doesn't show any existing wrapper for either major flavor of RPC.
Tres. -- ========================================================= Tres Seaver tseaver@palladion.com 713-523-6582 Palladion Software http://www.palladion.com
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Tres Seaver