I'd like to create the top five best seller of the products in each month.
I've heard that the annotations must be used for this case but I don't know how to use it.
Will anybody be kind enough to help me ??
You need to provide much more information before anyone can provide you with a useful answer. Describe what you know, what you've tried, elaborate on what you hope to accomplish.
In the mean time, you can learn about django's annotate() function, and see a few examples by reading the aggregation documentation for django.
annotate is not the only way to do it. You could also use an extra aggregation, though it might not be very efficient, and this will rely on sql specific to your database. This approach will not work in App Engine, but should in a SQL compliant database.
For example, say you had a Product model and a SalesOrder model, where the SalesOrder model has a line item for each product_id and order_date in it.
top_products = Product.objects.extra(
select={'num_orders':'select count(product_id) from app_product where app_salesorder.order_date > thirty_days_ago and app_product.id = app_salesorder.product_id'})
.order_by('-num_orders')[:5]
Related
I am using django-datatable-view to show my data. I have a scenario that I need to retrieve records from a model, that satisfy certain conditions.
For example, the request could be described as:
"SELECT * FROM model WHERE column_1='value_1' AND column_2='value_2'
How could I implement this? Actually, I saw the examples, but I don't have an efficient idea to do this.
Would you please help me in View definition or refer to proper sample?
It seems that we should implement a get_queryset(self) method to apply on targeted filters:
def get_queryset(self):
return Entity.objects.filter('item_1'='value_1')
While this could results in proper table values, but, the performance of loading decreases significantly.
Maybe other solutions could save the performance, or we should use other techniques like caching.
I think that the correct answer is pointed out in official documentation
You can filter QuerySet as it's shown in the example:
Entry.objects.filter(pub_date__year=2006)
For your case it could be:
Entry.objects.filter(column_1='value_1').filter(column_2='value_2')
Also it is possible duplicate of this topic
I'm new in Django and I'm giving myself a big headhache trying to structure this query.
I have a BaseProfile connected with a OneToOne field to User.
I'm specializing the profile in CustomerProfile connected with a OneToOne field to BaseProfile.
A CustomerProfile has a ManyToMany relationship with other CustomerProfile (so itself) through a RelatedCustomer model.
In the RelatedCustomer I specify the from_customer and to_customer Foreign Keys.
Maybe with an image you can understand better.
My problem:
Given a user.id I need to know all the other user.id of the customers that he is connected to (so passing through from_customer and to_customer):
So basically, first I need to dig from User to RelatedCustomer using reverse lookup, take all the set, and then going back to know the user.id of each customer in the set.
EDIT2:
What I've reached so far:
# This gives me back a customer profile given a user.id (2)
cm = CustomerProfile.objects.get(base_profile__user=2)
# M2M lookup. Given one customer returns all the RelatedCustomer relations
# that he has as a part of the 'from' M2M
cm.from_photographer.all()
Chaining the previous two: given a user.id I obtain a queryset of CustomerRelated relations:
rel = CustomerProfile.objects.get(base_profile__user=2).from_photographer.all()
This gives me back something like:
[<CustomerRelated: from TestCustomer4 to TestCustomer2 >,
<CustomerRelated: from TestCustomer4 to TestCustomer3 >]
Where in this case the user having a user.id=2 is the TestCustomer4.
My question:
So far so good, but now having this set how can I get all the user.id of the to_customer?
That is, how do I get the user.id of TestCustomer2 and TestCustomer3?
Firstly, this is not how you query the database in django. Secondly (since you're learning), it would be good to point out that you can run dbshell to try out different things. And lastly, this kind of problem is described in the documentation.
I am telling you this, because as a beginner, I also felt that it was a little difficult to navigate through the whole thing. The best way to find things is just to use google, and add a django at the end.
I know how you feel, the documentation search sucks, right? Heh, I feel you, that is why you always search the way I described it. Once you get a hang of the documentation, you will feel that the documentation title page is a little more intuitive.
Okay, so now to the answer:
To access a ManyToMany, OneToOne or ForeignKey field, you need to use a __ commonly known as dunder.
So, this is how I would go about doing this. Please note that there are other ways, and potentially better ways of doing this:
thing_I_want = RelatedCustomer.objects.get(to_customer__id=2)
Note, however that if you wanted to get a list of customers you would use filter(). Here is an example (which uses number of purchases as an example):
things_I_want = RelatedCustomer.objects.filter(to_customer__no_of_purchases=16)
Also note that the great thing about filter is that you stack one filter on top of another. You can read more about these features in the documentation link I provide below.
That will get you what you want. Now, you might have more queries regarding this, and how it all works together. Not to fear, please click this documentation link to check it out.
EDIT
Seems like what you want to do can be done by django, but if you want to do it using sql, then that is possible too. For example, SomeModel.objects.raw("SQL_HERE"). The name of the tables are usually <app>_<model>.
However, what you are asking can also be done in django, using the ORM. But it will be tricky.
Ok, as usual whenever you get the answer it always look much more easier than what you were expecting.
I guess this worked for me:
User.objects.filter(base_profile__customer_profile__to_customer__in=
User.objects.get(id=2).base_profile.customer_profile.from_customer.all())
Many thanks to #Games Brainiac
I'm building a web-site for a social interaction on a particular topic, based on threads, think of gmail, only public. There will also be some static info in vocabularies, as well as blog, how-tos, knowledge base, etc. It is django+postgres.
One of the most important requirements is a full-text search over all information, regardless of the type of a model. If the exact search phrase appears in the blog, and its twisted sister in messages, than a snippet from the blog entry should appear first in the search results and be followed by a snippet from the message. So, i need a table with all the texts indexed, and the links to _any_other_table_ in the db.
My first idea is to create a separate model with "loose reference", e.g.:
class Content(models.Model):
obj_id= CharField() # An id of the object of a given model.
model= CharField(choices=("Message", "BlogEntry", "HowTo", "EntityProfile",))
content_type= CharField(choices=("subject", "body", "description", "tags",))
body= TextField()
But it feels kind of wrong... This promises an unnecessary hassle around integrity of references when creating and re-linking instances.
So, the question is - is there any elegant solution that django would provide? What might be the most efficient architecture to solve the problem?
I am not asking for a direct answer, but rather a hint.
Thanks in advance!
I've had a lot of success working with this snippet, which uses PostgreSQL's tsearch2. I've tweaked it for various different purposes in various different ways, but basically it works very well, and is very easy to implement.
Thanks a lot for the hints!
while contenttypes is an ideal for this kind of task, it is really tempting to be DB independent
from what i've read so far, Solr is a reliable search engine, but i think, i'll go and try ElasticSearch via Haystack
thanks again!
I'd like to list all active products (from all or a specific category) in a template. I've looked almost everywhere and I simply cannot find a way to do this.
I want to display them in the footer of the shop (10 products from 1 category). That means show them without selecting product category.
Is this even possible? Products are only listed in the category template...
I'm using Satchmo 0.9.2
EDIT: Somehow I've missed this:
http://www.satchmoproject.com/docs/dev/customization.html
So it's solved...
Thank you!
this is a more general answer since there isnt any answer yet, so dont beat me. You also have to know that I never used satchmo, I never had a look at it.
But despite this, if I had to deal with your situation, I would have a look at the source code.
You might find answers there to develop something custom for your situation. This can be a tricky task but at least its worth a try.
There have to be models which store the data for your product and categories. Have a look at them and the views that retrieve the products from the database to render them. Also a look into the database cant hurt (think of phpmyAdmin to have a nice webbased interface).
It can be helpful to fire up your ./manage.py shell, import your/satchmos product and category models and play around with them.
A possible solution then could be to write a custom context_processor which retrieves the needed products/categories and passes these products from a category to your footer on a more global basis. Have a look here https://docs.djangoproject.com/en/1.3/ref/templates/api/#writing-your-own-context-processors. Maybe a custom middleware could also be a possibility. https://docs.djangoproject.com/en/dev/topics/http/middleware/#writing-your-own-middleware
I hope this helps. At least worth a try :)
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
Django dynamic model fields
Good Morning guys!
Scenario is the following. For some models on Django, I would like to allow the end user to define his own fields. It would be great if I could keep all Django awesome features like the ORM, so I can still do calls like field__gte to search on the model, still have field validation according to field type, etc. I've thought about two ways of doing this, and I'm more than open for new suggestions. Any feedback would be VERY appreciated.
The first approach, is the Entity-Attribute-Value ( http://en.wikipedia.org/wiki/Entity%E2%80%93attribute%E2%80%93value_model ), which django already has an app for. See http://code.google.com/p/django-custom-field/
I think this would be an OK solution, but I lose the ability to do "mymodel.objects.filter(custom_field_x=something)". Maybe there's a way to regain the ORM, any ideas? But I've heard so many bad stories about this method that I'm little scared to use it.
The second approach would be to have a database table for each of the users (probably no more than a 1000). I've read django has something in the lines of inspectdb, which actually checks which fields are there and produces the model for you. This could be useful but I think maybe I should store the fields this particular user has created and somehow dinamically tell django, hey, we also have this fields in this model. Is this possible? I know it's generally bad to have different tables for each user, but considering this scenario, how would you guys rate this method, would it be ok to have one table for each user?
The model that requires custom fields is for example Person. They might want a custom field to store address, blood type, or any other thing.
MANY THANKS in advance! Have a nice sunday!
Very similar: How to create user defined fields in Django -- but only talks about the EAV, which I would like to avoid. I'm open for new ideas!
One approach is to use a NoSQL document-based solution such as MongoDB which allows you to store objects that have a fluid structure (no such restrictions as pre-defined columns).
Pros:
No restriction on custom field types, number of types of fields, etc.
Retains ORM functionality (django-mongodb)
Other various benefits of NoSQL - which you can read about online
Avoids EAV
Cons:
Need to setup NoSQL server
Additional knowledge required on NoSQL concepts (documents vs. tables)
You may have to maintain two databases - if you decide not to migrate your entire solution to NoSQL (multi-db)
EDIT:
After reading the comments its worth pointing out that depending on which NoSQL solution you go with, you may not need reversion support. CouchDB, for example has built in support for document versioning.
what about creating another model for storing user_defined_fields?
class UserDefinedField(models.Model):
#..................
user = models.ForeignKey(User)
field_name = models.CharField(max_length=50)
field_value = models.TextField()
Then you can do UserDefinedField.objects.filter(field_name=some_name,field_value=somevalue)