Re: Globally unique IDs
Re: Globally unique IDs
- Subject: Re: Globally unique IDs
- From: Alexander Spohr <email@hidden>
- Date: Fri, 6 Feb 2004 23:05:30 +0100
in fact apple encourages you to use unique pks. i forgot where, but
there is some document explaining how to do it with eof. they use time
and machine ids and someting. i think i remeber 80 bit or 80 byte...
googling for "eomodeler unique primary key" finds:
Adaptor-Generated Primary Key
In EOF's default primary key mechanism, the EOAdaptorChannel generates
the primary keys. It collaborates with the database server to maintain
a linear sequence of nonrepeating primary keys per entity. The primary
key attribute must not be a class property. If the type of the primary
key attribute is a 12-byte NSData, EOF generates unique primary keys
without going to the database.
not sure if that's what your'e looking for :)
atze
Am 06.02.2004 um 19:45 schrieb Colin O'Brien:
Hi,
we are working on a new system, where we will be moving data between
different databases.
This will require objects with a simple ID that is globally unique.
It seems the automatic private key mechanism in WO only provides
unique keys within a single database.
It seems we could get a truly unique ID using VMID.
It further seems we could create our own "PK's" in awakeFromInsertion.
The questions then would be
* is there going to be a noticeable performance hit using VMID's (40
bytes) compared to the more typical int?
more concerned about retrieval performance than update performance
* would it be better to use the built-in PK system and have a separate
column for the VMID?
particularly thinking about how relationships might work
We are planning on using MySQL.
We looked at both MySQL and PostgreSQL and while PostgreSQL seems the
better database system, MySQL seems better supported in WO.
Thanks for any help
Colin
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