I have Entity (not MappedSuperclass) Person (with id, name, surname).
I also have Entity Employee extends Person (with other attributes, unimportant).
Inheritance Strategy is single table.
Now I want to create a namedQuery like this:
SELECT emp FROM Employee emp WHERE emp.name = ?1
In the IDE I get:
the state field path emp.name cannot be resolved to a valid type
I think the problem is that the attribute belongs to the superclass entity.
So far, I haven't found any solution other than using the TYPE operator to perform a selective query on Employee instances.
I'd like to perform the query above. Is that possible?
I'm on EclipseLink/JPA 2.0
Your JPQL seems valid. Did you try it at runtime? It could just be an issue with your IDE.
(include your code)
Person has to be #MappedSuperclass.
http://www.objectdb.com/api/java/jpa/MappedSuperclass
Furthermore, you should use named parameters, e.g. :name instead of ?...
Related
After trying for hours, I am coming here. I have the following model:
class Items(models.Model):
date=models.DateField()
giver=models.IntegerField()
Class Givers(models.Model):
name=models.CharField(max_length=25)
Basically, an item could be given by donators from Givers model or it could be bought by user. If given, giver field stores id from Givers model. Else, it is 0. Now I want a query that will list out my items. If giver>0, I need to show the name of the giver. I can't create relationships here. This query has brought me so close and works like a charm on literal values but I want to provide the 'giver' field instead:
data=Items.objects.all().extra(select={'giver_name':giver_name(1,False)}).values('giver_name','id','date')
It works like a charm even if given any number (exists or not exists). But I want to do something like this but it fails cos field is not found or undefined:
data=Items.objects.all().extra(select={'giver_name':giver_name(giver,False)}).values('giver_name','id','date')
giver_name is a function that accepts id of a giver and a boolean value and returns a name.
I have a below use case:
I have a method that accepts a list of strings. For each of the strings, I need to create a property under an existing google data store entity A
Example: I have an existing entity Person with properties fname and lname.
If the input list has strings - address, city, I need to update the entity Person to include these new properties address and city.
I'm coding this use case in Python. Any suggestions on how I can achieve this?
So the best way to do this is to let your class inherit ndb.Expando. The difference between Expando and Model is that you can always add attributes to an Expando entity and be able to store it in the Datastore.
Knowing this, there are several ways to proceed, but I am guessing you’re also going to need to use Python’s setattr(object, name, value) method to pass the attribute name from a string.
Take a look at the Expando model class: https://cloud.google.com/appengine/docs/standard/python/ndb/creating-entity-models#creating_an_expando_model_class
class Person(ndb.Expando):
pass
person = Person(fname='some', lname='body')
person_key = person.put()
...
person = person_key.get()
person.city = 'San Francisco'
person.address = '1234 Main St.'
person.put()
Let say I have two fields in a django form country and state.I want the values of state to relatively change with the values of country.i.e. I want the state field to list out the states of the country that user has selected. Also the state field should be empty during form initiation.I know that this can be done using java script and other scripts.But,I would like to know if there are any conventional methods exists in django to do the same.???
Sounds like you need to create a model for Country and State.
State model should have a foreign key linking to Country. This means many states can be related to one country. Then, populate the tables with all countries and states you want.
In your form, you can override the 'init' method with custom behavior. So, if you have declared a field 'state' then you can do something like self.fields['state'].choices = State.object.filter(country_id=some_country_id). This assumes you have some_country_id already and you can pass this through as a kwarg during instantiation.
I want to attach a field value (id) to a QS like below, but Django throws a 'str' object has no attribute 'lookup' error.
Book.objects.all().annotate(some_id='somerelation__id')
It seems I can get my id value using Sum()
Book.objects.all().annotate(something=Sum('somerelation__id'))
I'm wondering is there not a way to simply annotate raw field values to a QS? Using sum() in this case doesn't feel right.
There are at least three methods of accessing related objects in a queryset.
using Django's double underscore join syntax:
If you just want to use the field of a related object as a condition in your SQL query you can refer to the field field on the related object related_object with related_object__field. All possible lookup types are listed in the Django documentation under Field lookups.
Book.objects.filter(related_object__field=True)
using annotate with F():
You can populate an annotated field in a queryset by refering to the field with the F() object. F() represents the field of a model or an annotated field.
Book.objects.annotate(added_field=F("related_object__field"))
accessing object attributes:
Once the queryset is evaluated, you can access related objects through attributes on that object.
book = Book.objects.get(pk=1)
author = book.author.name # just one author, or…
authors = book.author_set.values("name") # several authors
This triggers an additional query unless you're making use of select_related().
My advice is to go with solution #2 as you're already halfway down that road and I think it'll give you exactly what you're asking for. The problem you're facing right now is that you did not specify a lookup type but instead you're passing a string (somerelation_id) Django doesn't know what to do with.
Also, the Django documentation on annotate() is pretty straight forward. You should look into that (again).
You have <somerelation>_id "by default". For example comment.user_id. It works because User has many Comments. But if Book has many Authors, what author_id supposed to be in this case?
I have a Product entity and a Shop entity.
A shop can have 0 to n products and a product can be in only one shop.
The product entity table is thus refering to the Shop entity through a shop_id table field.
When querying for the products of a given shop using doctrine query builder, we can do this:
$products = $this->getDoctrine()->getRepository('MyBundle:Product')
->createQueryBuilder('p')
->where('p.shop = :shop')
->setParameter('shop', $shop) // here we pass a shop object
->getQuery()->getResult();
or this:
$products = $this->getDoctrine()->getRepository('MyBundle:Product')
->createQueryBuilder('p')
->where('p.shop = :shopId')
->setParameter('shopId', $shopId) // we pass directly the shop id
->getQuery()->getResult();
And the both seem to work... I'm thus wondering: can we always pass directly entity ids instead of entity instances in such cases (ie: on a doctrine entity field that refers to another entity)?
I initially thought that only the first example would work...
According to the Doctrine documentation, you can pass the object to setParameter() if the object is managed.
extract from the documentation:
Calling setParameter() automatically infers which type you are setting as value. This works for integers, arrays of strings/integers, DateTime instances and for managed entities.
for more information, please see:
http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/query-builder.html#binding-parameters-to-your-query
I might be wrong, but I think that if you pass object instance instead of id number, Doctrine will automatically call $instance->getId() making your two queries the same when translated into SQL (even DQL).