Is there a way to define autoincrement Field in peewee.
I understand we could define sequence but the need to create the sequence manually and not managed by create_tables deters me from using it. ( The build process is managed by create tables and I would prefer not to add manual steps )
import peewee
class TestModel(peewee.Model):
test_id = peewee.BigIntegerField(sequence='test_id_seq')
Alternate to the above code I would rather have. As most databases have serial field I dont see a point maintaining a sequence.
import peewee
class TestModel(peewee.Model):
test_id = peewee.AutoIncremenetIntField()
Either you can use PrimaryKeyField() as #wyatt mentioned in comment
or you can use Playhouse- Signal Support (peewee extensions)
from playhouse.signals import Model, pre_save
class MyModel(Model):
data = IntegerField()
#pre_save(sender=MyModel)
def on_save_handler(model_class, instance, created):
# find max value of temp_id in model
# increment it by one and assign it to model instance object
next_value = MyModel.select(fn.Max(MyModel.temp_id))[0].temp_id +1
instance.temp_id = next_value
The given answers here are outdated but this was still my first Google search result.
Peewee has a special field type for an auto incrementing primary key called AutoField:
The AutoField is used to identify an auto-incrementing integer primary
key. If you do not specify a primary key, Peewee will automatically
create an auto-incrementing primary key named “id”.
Take a look at the documentation. Example usage:
class Event(Model):
event_id = AutoField() # Event.event_id will be auto-incrementing PK.
Related
When I pass an instance of a model to a query for use as the fk ref, I have seen some syntax where the instance itself is suitable but in my repro it fails.
for example:
model_a = ModelA(name='bar')
model_a.save()
Model_b.get_or_create(name='foo', model_a_id=model_a)
# versus
Model_b.get_or_create(name='foo', model_a_id=model_a.get_id())
What base model feature enables the first syntax?
I am using peewee v2.7.4.
Have you tried just assigning the model instance to the foreign-key name?
Model_b.get_or_create(name='foo', model_a=model_a)
If all you have is an integer ID for model_a, the above should also work.
In my django model I would like to set the field unique_id below to be the primary key as this will be the field used in queries for the model. It satisfies unique=True and null=False. However as django sets an AutoField to primary key in the background I'm unsure whether a CharField (which uses a unique 3 character code) is suitable as a primary key or whether this will be sub-optimal?
class PaymentMethod(models.Model):
unique_id = models.CharField(max_length=3)
last_updated = models.DateTimeField(auto_now=True)
There is nothing wrong with setting the CharField to be a primary key, by changing the model to be:
class PaymentMethod(models.Model):
unique_id = models.CharField(max_length=3, primary_key=True)
last_updated = models.DateTimeField(auto_now=True)
In actual fact if the unique_id is the field you will be querying it makes perfect sense to use it. Your other options are to use your existing model but with unique=True:
class PaymentMethod(models.Model):
unique_id = models.CharField(max_length=3, unique=True)
last_updated = models.DateTimeField(auto_now=True)
In this case your primary key will be an auto incrementing integer as you previously stated.
Another option depending on the number of records you are looking to store in the PaymentMethod models; and where the data is used elsewhere within your application. Is too look into using a model choices field. The model choices field might be on your payments or order model (depends on your application and what you are trying to do). This removes the need for a foreignkey and potentially reduces the number of queries in your app.
It could look something like this:
class Payment(models.Model):
VISA = 'VIS'
CREDIT = 'CRE'
MASTER_CARD = 'MAS'
PAYPAL = 'PAL'
PAYMENT_OPTIONS= (
(VISA, 'Visa'),
(CREDIT, 'Credit Card'),
(MASTER_CARD, 'Master Card'),
(PAYPAL, 'Paypal')
)
items = models.ForeignKey(Item)
date = models.DateField(auto_now=True)
...
payment_method = models.CharField(max_length=3, choices=PAYMENT_OPTIONS, default=VISA)
The PAYMENT_OPTIONS can be used to render dropdown boxes on the forms when using django model forms. Otherwise the users selection is limited to the options listed within this model.
This method would be a lot more efficient if you only have a small subset of PaymentMethod(s).
It's possible to use CharField as primary key. You just have to mark the field as primary key.
field_name = models.CharField(primary_key=True, max_length=100)
But I wouldn't recommend it because:
Primary keys are used in urls (typically in Rest APIs) - but not all characters are allowed in urls
DRF (django-rest-framework) use urls patterns that don't catch some characters by default (for example ".")
Primary keys must be unique - it's harder to accomplish it if the field is a string, especially when you let users to define it
This is my code:
$get_all = Geo_Postal_us::findOrFail($postal);
With this query, Laravel tries to find the id field in the table.
I don't have an id field. I use the postal column as primary key.
How do you set the function to find value in postal column and not search from id column?
Thanks,
You could create the behaviour you are looking for with the following:
Geo_Postal_us::where('postal', $postal)->firstOrFail();
Laravel by default is searching for the "id" column inside the table if you are using find(). To avoid running into errors here and maybe later, you should always tell laravel that you did take another name for your primary field.
To do that, in your Geo_Postal_us just edit as the following:
class Geo_Postal_us extends Model
{
protected $primaryKey = 'postal'; //tell laravel to use 'postal' as primary key field
...
...
I ran into this issue within Voyager and it really drove me nuts :).
Hope this helps some people as they google the issue.
I see the document
https://developers.google.com/appengine/docs/python/ndb/keyclass#Key_integer_id
Returns the integer id in the last (kind, id) pair, or None if the key
has an string id or is incomplete.
see I think the id of a key can be a int ; so I write
r = ndb.Key(UserSession, int(id)).get()
if r:
return r.session
but the dev_server.py , will always raise
File "/home/bitcoin/down/google_appengine/google/appengine/datastore/datastore_stub_util.py", line 346, in CheckReference
raise datastore_errors.BadRequestError('missing key id/name')
BadRequestError: missing key id/name
I chanage the int(id) -> str(id)
seems right ;
so my question is , How to use ndb key with integer_id ?
the model is
class UserSession(ndb.Model):
session = ndb.BlobProperty()
The type of the id you use when reading the entity must match the type of the id you used when you wrote the entity. Normally, integer ids are assigned automatically when you write a new entity without specifying an id or key; you then get the id out of the key returned by entity.put(). It is generally not recommended to assign your own integer ids; when the app assigns the keys, the convention is that they should be strings.
There's an easier way to fetch:
UserSession.get_by_id(int(id))
https://developers.google.com/appengine/docs/python/ndb/modelclass#Model_get_by_id
If that doesn't work, I suspect that id is wrong or empty.
There must be something wrong with your variable 'id'.
Your code here should be no problem, and it's better to user long instead of int.
You can try your code on interactive console of development server with specific integer id.
It may be easier to identify your entities in the sessions with their keys instead of their ids. There really is no need to extract the ID from the key to identify the session (other than maybe saving a bit of memory. I think the way your thinking is based on a RDB. I learned that using the key actually makes entity/session identifications easier.
'id' is also a python builtin function. Maybe you are taking that by mistake.
I want to get an entity key knowing entity ID and an ancestor.
ID is unique within entity group defined by the ancestor.
It seems to me that it's not possible using ndb interface. As I understand datastore it may be caused by the fact that this operation requires full index scan to perform.
The workaround I used is to create a computed property in the model, which will contain the id part of the key. I'm able now to do an ancestor query and get the key
class SomeModel(ndb.Model):
ID = ndb.ComputedProperty( lambda self: self.key.id() )
#classmethod
def id_to_key(cls, identifier, ancestor):
return cls.query(cls.ID == identifier,
ancestor = ancestor.key ).get( keys_only = True)
It seems to work, but are there any better solutions to this problem?
Update
It seems that for datastore the natural solution is to use full paths instead of identifiers. Initially I thought it'd be too burdensome. After reading dragonx answer I redesigned my application. To my suprise everything looks much simpler now. Additional benefits are that my entities will use less space and I won't need additional indexes.
I ran into this problem too. I think you do have the solution.
The better solution would be to stop using IDs to reference entities, and store either the actual key or a full path.
Internally, I use keys instead of IDs.
On my rest API, I used to do http://url/kind/id (where id looked like "123") to fetch an entity. I modified that to provide the complete ancestor path to the entity: http://url/kind/ancestor-ancestor-id (789-456-123), I'd then parse that string, generate a key, and then get by key.
Since you have full information about your ancestor and you know your id, you could directly create your key and get the entity, as follows:
my_key = ndb.Key(Ancestor, ancestor.key.id(), SomeModel, id)
entity = my_key.get()
This way you avoid making a query that costs more than a get operation both in terms of money and speed.
Hope this helps.
I want to make a little addition to dargonx's answer.
In my application on front-end I use string representation of keys:
str(instance.key())
When I need to make some changes with instence even if it is a descendant I use only string representation of its key. For example I have key_str -- argument from request to delete instance':
instance = Kind.get(key_str)
instance.delete()
My solution is using urlsafe to get item without worry about parent id:
pk = ndb.Key(Product, 1234)
usafe = LocationItem.get_by_id(5678, parent=pk).key.urlsafe()
# now can get by urlsafe
item = ndb.Key(urlsafe=usafe)
print item