[PonyORM-list] get PK of the record before committing it to DB

[Вадим Бажов]

It doesn't work for me.

I have a Customers entity with 'licences' field as Set which is in 
relation with Licences entity which have back relation field 'customer' 
as Required(Customers).

Hence i must supply customer's id for 'customer' field while add licence 
to a customer object.

I must do the following:

cust = Customer(name='asd',email='asd at qwe.com') <- it doesn't create id
before commiting it.

lic = cust.licences.add(
     customer=cust.id, <- required filed in DB model. related to 
Customers record by PK.
     x=1,
     y=2
)

But newly created object has no id since it wasn't written to DB yet.

May be Pony allows child entities without Required fields linking entity 
back to a parent entity, but i didn't try it.

On 25.03.2015 11:03, Matthew Bell wrote:
> You don't need the PK to add a relation, you can do:
>
> cust = Customers(name='GazMyas',city='Chelyabinsk')
> cust.licenses.add(License(x=1, y=2))
> cust.licenses.add(License(x=3, y=4))
>
> So, create the customer, then loop over all licenses for that 
> customer, doing customer.licenses.add
>
> You can then commit after each iteration, or just once at the end of 
> the script, up to you.
>
> On 25 March 2015 at 08:28, Вадим Бажов <vadim at ideco.ru
> <mailto:vadim at ideco.ru>> wrote:
>
>     Hello happy pony users and devs !
>
>     I do an import from old db to a new one, driven by pony orm.
>     Import iterates over records of customers and their related
>     licences, fetched from an old DB. So we have to fill two tables in
>     new DB: Customers table and Licence table with records, which have
>     one2many relations (one Customer can have many Licences, by PK).
>     PK is an autoincrementing integer in both tables.
>
>     Within *each iteration* of import i need to write one Customer
>     record and its Licences records to new DB. Licence records should
>     have customer_id fields filled up with corresponding Customer PKs.
>     Here we have a problem:
>
>     If we create an object of an entity Customers : cust =
>     Customers(name='GazMyas',city='Chelyabinsk') , it wont be recorded
>     to a DB exactly at this moment and we wont able to use its ID (pk
>     of the record) to bind Licence records to it. In other words there
>     is no 'cust.id <http://cust.id>' element at this moment.
>
>     We can do a 'commit()' each time we create a Customer object.
>     After that 'cust.id <http://cust.id>' comes ready. But in case of
>     monstrous imports with over 20 000 records committing every record
>     to hdd slows down the import process to hours. And hangs up your
>     server hard drive. Anyway, it's a bad practice to commit every
>     record walking the huge array of incoming data.
>
>     So, by now, I fill up two dicts with Customers records,
>     incrementing their ID's manually (customer_id += 1) and Licences
>     records bound to this pre-calculated ID's. When dicts are ready, I
>     write them to a new DB walking through them.
>
>     Is there a better way to complete a data import without filling up
>     transition dicts and calculating autoincrement IDs by hand ? Can I
>     somehow use PKs of the records before committing them to DB ?
>
>     _______________________________________________
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>
>
>
>
> -- 
> Regards,
>
> Matthew Bell
>
>
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