I would like to create a Model with peewee where a Charfield is either null or a unique value. For example, I would think that it could be done with constraints, Meta, or perhaps both, but trying to do so is giving me a headache.
Does anyone have a solution for this in peewee?
The answer, as with most things in peewee, is pretty simple. Adding unique=True and null=True looks to work well.
class myModel(db.Model):
id = PrimaryKeyField()
myCharField = CharField(max_length=6, unique=True, null=True)
Related
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.
UPDATE: ADDED A BOUNTY. PLEASE PROVIDE AN EXAMPLE AND I WILL ACCEPT THE BEST ANSWER
UPDATE 2: Explicit example now included
Carrying on from the same project, where I asked about bulk_create in a separate thread.
I was wondering if there is a way to essentially "bulk_save" - insert if non-existent or simply update if it already exists.
For example:
class Person(models.Model):
first_name = models.CharField(max_length=30)
last_name = models.CharField(max_length=30)
height = models.DecimalField(blank=True, null=True)
weight = models.DecimalField(blank=True, null=True)
I have a list of dictionaries with key-value pairs for these fields. I would like to filter by name, and then update the height and/or weight as these my players are still growing and conditioning. If there is no easy way to "bulk_save", a bulk update would also be helpful.
Reference: June 8, 2012 - "get_or_create()" patch at django project
Bulk_update reference
I just did a variation of the update_many function listed below I seem to have improved speeds tremendously already.
http://people.iola.dk/olau/python/bulkops.py
UPDATE - apparently DSE2 is also an option.
https://bitbucket.org/weholt/dse2
Will update with speed tests tomorrow.
I'm accessing emails in my email server, taking the body of each email and then applying regular expressions to find the data necessary to populate my Django model.
This all works fine except for one field, which is linked as a foreign key to another model field. Despite the value in my email being the same as the one in listed in my other model, it fails....
The error:
ValueError: Cannot assign "'Humanities'": "Subject.faculty" must be a "Faculty" instance.
For example, say each school subject has to be part of a faculty. When populating the database via a form, for the Subject's faculty field I drop down the menu to a list of faculty values/instances as there is a foreign key relationship defined in my model i.e. for the faculty field I can choose from Humanities, Art, Design Technology etc.
But when I find the value 'Humanities' in my email and try to add it to the database model, I get the error above.
Anyone shed any light on this? Am I being stupid or is it more than a ValueError as to me, the values are the same in both cases
Thank you
More code as requested:
class Faculty(models.Model):
name = models.CharField(primary_key=True, max_length=50)
leader = models.CharField(max_length=50)
email = models.EmailField()
mailing_list = models.ManyToManyField("Contact", null=True)
class Subject(models.Model):
name = models.CharField(max_length=50)
faculty = models.ForeignKey(Faculty, to_field="name")
faculty_head = models.CharField(max_length=50)
It sounds like you are trying to assign a string "Humantities" to a ForeignKey relationship. This doesn't make sense. You need to either find or create the actual Faculty object with the name "Humanities" and assign it to the Subject. Something like this in your view (depending on how your form is set up):
if form.is_valid():
faculty_str = form.cleaned_data['faculty']
(faculty, was_created) = Faculty.objects.get_or_create(name=faculty_str, ...)
# It's hard to tell if you are using a ModelForm or just a normal Form. Anyway, assume we already have access to the Subject object
subject.faculty = faculty
subject.save()
get_or_create()
Your value is 'Humanities' perhaps you mean to search for Humanities (without quotes).
You need to create a Faculty instance first.
faculty = Faculty(name='', leader='', email='')
faculty.save()
subject.faculty = faculty
subject.save()
I have a bunch of Users. Since Django doesn't really let me extend the default User model, they each have Profiles. The Profiles have a referred_by field (a FK to User). I'm trying to get a list of Users with >= 1 referral. Here's what I've got so far
Profile.objects.filter(referred_by__isnull=False).values_list('referred_by', flat=True)
Which gives me a list of IDs of the users who have referrals... but I need it to be distinct, and I want the User object, not their ID.
Or better yet, it would be nice if it could return the number of referrals a user has.
Any ideas?
Took me a long time to wrap my head around this, but I think I finally got it figured out:
affiliates = User.objects.annotate(num_referrals=Count('referrals')).filter(num_referrals__gt=0)
I didn't think I'd be able to use the reverse relationship
referred_by = models.ForeignKey(User, null=True, blank=True, related_name='referrals')
in Count(), nor did I think you could use the annotated value in the filter... that's pretty cool. I still wish you could use GROUP BY without having to annotate stuff (assuming I didn't need the count).