[sqlalchemy] Re: Filling foreign key with mapping
Thanks for these interesting articles. I was blind ! Why using a small integer surrogate primary key instead of two chars primary key, why ? =) As described in the article, I think I am abusing of surrogate primary keys. Our database schema is not yet finalized, I am going to fix this right now. Nevertheless, in some others tables of our schema, I think a surrogate can not be avoided. It will appear in some others tables and I am expecting millions of entries. That's why I prefer a small integer surrogate primary key instead of a 50 or 100 bytes string primary key. In such cases, I was asking about an elegant way to find the unique name along the surrogate primary key. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: Filling foreign key with mapping
eh, i use surrogate keys all the time :) On Dec 6, 2007, at 4:45 AM, paftek wrote: Thanks for these interesting articles. I was blind ! Why using a small integer surrogate primary key instead of two chars primary key, why ? =) As described in the article, I think I am abusing of surrogate primary keys. Our database schema is not yet finalized, I am going to fix this right now. Nevertheless, in some others tables of our schema, I think a surrogate can not be avoided. It will appear in some others tables and I am expecting millions of entries. That's why I prefer a small integer surrogate primary key instead of a 50 or 100 bytes string primary key. In such cases, I was asking about an elegant way to find the unique name along the surrogate primary key. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: Filling foreign key with mapping
I believe what you need to do is get an instance of a language object
something like:
item.Language = session.query(Language).filter_by(name='en').first()
There maybe a better way to do this, but its how I currently do it (so
if there is a better way I would like to know).
paftek wrote:
Hi,
Sorry for this meaningless subject !
I am learning SQLAlchemy and I installed version 0.4.1 few days ago.
My problem is probably easy to solve. I swear I have read a good part
of the documentation, and searched this group ! But...
Short example. Two tables :
- languages having a sequence as primary key and a column of unique
short names ('en', 'fr', etc.)
- items having a foreign key on 'language_id' (see Python code
below)
When creating a new item, it is not significant to fill the foreign
key value with a integer. I wish the mapper had a way to find it
through the unique language name :
item = Item()
item.name = 'A great item'
item.language_name = 'en'
session.save(item)
Please, how to do that ?
Cheers
languages_table = Table('languages', metadata,
Column('language_id', PGInteger, Sequence('language_id_seq'),
primary_key=True),
Column('name', Unicode(), nullable=False, unique=True)
)
items_table = Table('items', metadata,
Column('item_id', PGInteger, Sequence('item_id_seq'),
primary_key=True),
Column('language_id', PGInteger,
ForeignKey('languages.language_id'), primary_key=True),
Column('name', Unicode(), nullable=False)
)
class Item(object): pass
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