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

Matthew Bell matthewrobertbell at gmail.com
Wed Mar 25 09:03:52 UTC 2015

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> 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'
> element at this moment.
> We can do a 'commit()' each time we create a Customer object. After that '
> 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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Matthew Bell
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