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Re: Non-integer primary keys
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Re: Non-integer primary keys


  • Subject: Re: Non-integer primary keys
  • From: Steve Sharman <email@hidden>
  • Date: Tue, 3 Aug 2004 00:28:30 +0100

Thanks for the reference Art - that's what I was looking for. And you're right - what I'm thinking about doesn't make any sense from a WebObjects viewpoint - I was mulling over various models for how a distributed or mobile WO application might work from an object synchronisation perspective.

What I was thinking was that if I could ensure that each separate application (each with it's own application server and database) used completely unique keys (e.g. there would be no possibility of a "person" object on app server 1 having the same PK as another "person" object on app server 2), then I could use the underlying database middleware to keep the two databases and applications in sync. Not going to work... but still, it's not something that I'm too worried about at this point.

Thanks,

-- Steve

On 2 Aug 2004, at 20:23, Art Isbell wrote:

On Aug 2, 2004, at 12:01 AM, Steve Sharman wrote:

I'd like in the future to be able to implement a mechanism where I can be absolutely sure that my primary keys are completely unique across all instances of an application, even if those applications are running on completely different database and application servers.

I must not be understanding your needs. Primary key values are unique within a table in a database. The database guarantees uniqueness. They have nothing to do with application instances or where the app or database are running. All instances of an EO within different editing contexts and in different app instances will have the same primary key value, that which was fetched from the database. This must remain true for EO caching to work correctly and for the correct mapping of an EO to a database row.


I've seen a few references on the list to character primary keys, but nothing much which is specific on implementation. Is there anywhere on the web or in the development documentation that shows how this might be done - presumably it's easy to set up the primary key for an EO as being of character type, it's the PK generation mechanism that I'd like to properly understand.

http://developer.apple.com/documentation/WebObjects/ Enterprise_Objects/Saving/chapter_8_section_5.html#//apple_ref/doc/ uid/TP30001011-DontLinkChapterID_14-TPXREF151 discusses the EOF hooks that support custom primary key generation. But how to generate unique primary key values is up to you.


Aloha,
Art
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  • Follow-Ups:
    • Re: Non-integer primary keys
      • From: Dov Rosenberg <email@hidden>
References: 
 >Non-integer primary keys (From: Steve Sharman <email@hidden>)
 >Re: Non-integer primary keys (From: Art Isbell <email@hidden>)

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