Subject: Re: [Pharo-project] relational database and id field
One more remark,
Since you're storing objects into a RDBMS, I guess what you're trying to express into "the relational world" is a notion of pointer (such as an object contains a collection of something in one of its instance variable, or a child has a mother kinda relationship, link). �In that case, to save you headaches and lots of "weird object-oriented modeling", an oid (object id) is what is used normally. �Any sequence (the shorter the better, don't use GUID for instance!) would do...
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Benoit St-Jean
Yahoo! Messenger: bstjean
A standpoint is an intellectual horizon of radius zero.
(Albert Einstein)
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From: Alexandre Bergel <
alexandre.bergel@me.com>
To: Benoit St-Jean <
bstjean@yahoo.com>
Cc:
Pharo-project@lists.gforge.inria.fr
Sent: Thu, April 7, 2011 9:49:11 AM
Subject: Re: [Pharo-project] relational database and id field
> Normally, you should always have a primary key to uniquely identify a record in a database table. �If you have an attribute (or a set of attributes) that can uniquely identify your ComicBook, you don't need an id field. �BUT, if you tell me you're going to store lots and lots and lots of those ComicBook instances, having an id (integer) as the primary key has potential non-negligeable advantages over, say, something like a name. �Mainly because an id (let's suppose it's an INT) takes way less storage than say a name (VARCHAR(30) for instance) and thus more index records can fit into the key buffer in memory.
Ok, I understand.
> 1) yes, always provide a primary key
> 2) if you have already A primary key (even a composite one)
> � �2a) if you need performance and are gonna store LOTS of those objects, the smaller the key the better so you could create a surrogate key (the id key) instead of using the "real" primary key
> � �2b) if performance is not an issue, you can use what is already available that uniquely identifies your object (row) in the database table
Thanks!
> P.S. �Are you using a particular OO-RDBMS framework?
No, I am correcting a student thesis :-)
I would probably not use SQL if I had to :-)
Cheers,
Alexandre
>
> -----------------
> Benoit St-Jean
> Yahoo! Messenger: bstjean
> A standpoint is an intellectual horizon of radius zero.
> (Albert Einstein)
>
>