[PonyORM-list] get PK of the record before committing it to DB
Вадим Бажов
vadim at ideco.ru
Fri Mar 27 16:46:47 UTC 2015
It was simple !
Just rewrote the whole import procedure in the first mentioned way.
Works as expected.
Thank you Alexander and have a nice weekend !
On 27.03.2015 17:53, Alexander Kozlovsky wrote:
> You can just write:
>
> cust = Customer(name='asd',email='asd at qwe.com <mailto:asd at qwe.com>')
> lic = License(customer=cust, x=1, y=2)
> key1 = Key(license=lic, a=1, b=2)
> key2 = Key(license=lic, a=3, b=4)
>
> or, equivalently:
>
> cust = Customer(name='asd',email='asd at qwe.com <mailto:asd at qwe.com>')
> lic = cust.licenses.create(x=1, y=2)
> key1 = lic.keys.create(a=1, b=2)
> key2 = lic.keys.create(a=3, b=4)
>
> The add() method of collection did not return anything, but the
> create() method returns newly created object.
>
>
>
> On Fri, Mar 27, 2015 at 6:31 PM, Вадим Бажов <vadim at ideco.ru
> <mailto:vadim at ideco.ru>> wrote:
>
> Hello Alexander.
> Seems to work when i pass customer as an object, thank you.
> But what if i have another child entity for Licences, for example
> Keys entity which has many to one relation to Licences.
> And, during the same iteration, i need to add available keys to
> newly added Licence of a newly created Customer.
>
> I have Customers -> Licences -> Keys data structure. That's a
> final approach, i swear ! ))
> Keys has Required relation field to Licences, f.e. 'licence_id'.
> Licences has Required field to Customers, f.e. 'customer_id'.
>
> I can add a Licence object to a Customer, passing Customer object
> to add() method.
> But what should i do if i need to add() a Key to an added Licence.
> cust.add() returns None so i cant see the use if it in anyway.
>
> Is there a way to get a last added item to an entity object ?
>
>
> On 27.03.2015 14:53, Alexander Kozlovsky wrote:
>> > cust.licenses.add(License(x=1, y=2))
>>
>> I think this should works good if the `customer` attribute of the
>> License class was defined as Optional. But since it is Required,
>> the License constructor will raise exception here. So it is
>> necessary to specify customer right at the moment of the license
>> creation. But it need to be specified as an object and not as id
>> value.
>>
>>
>> On Fri, Mar 27, 2015 at 3:33 PM, Matthew Bell
>> <matthewrobertbell at gmail.com
>> <mailto:matthewrobertbell at gmail.com>> wrote:
>>
>> The way you are creating licenses is different from how I
>> suggested it:
>>
>> cust.licenses.add(License(x=1, y=2))
>>
>> You add an instance of License to the cust.licenses set.
>>
>> That should work.
>>
>> On 27 March 2015 at 11:32, Вадим Бажов <vadim at ideco.ru
>> <mailto:vadim at ideco.ru>> wrote:
>>
>> 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
>> <mailto:asd at qwe.com>') <- it doesn't create id before
>> commiting it.
>>
>> lic = cust.licences.add(
>> customer=cust.id <http://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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>>> /ponyorm-list
>>
>>
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>>
>>
>>
>> --
>> Regards,
>>
>> Matthew Bell
>>
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>> /ponyorm-list
>>
>>
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