I have a reservation system and I want to store the user_id of people who buy the tickets of an event, with the number of tickets bought in an array of hashes. So, it would be like:
[{"id" => "1", "no" => "3"}, {"id" => "4", "no" => "2"}]
It means that user_id 1 reserved 3 seats in this event ...
The database I'm using is PostgreSQL and I defined this field as text, array: true with the name of reservations to use the power of array in psql.
The problem is to search this field to show each user his reservations and corresponding quantity. I need to define a scope in the Event model and call it from the User controller. As a result, each user can see his reservations in his dashboard. I tried many many ways but still have problem. Any idea and help would be great.
How about creating separated table and store there user_id and seats_count. You can name it UserReservation. You can then update User model and have
class User
has_many :user_reservations
end
so you can easily fetch all user reservations by calling current_user.user_reservations.joins(:event)
Related
This are my model with some of the fields:
class Advertisers(models.Model):
account_manager_id = models.ForeignKey(AccountManagers, on_delete=models.CASCADE,null=True, db_column='account_manager_id',related_name="advertisers")
class AdvertiserUsers(models.Model):
user_id = models.OneToOneField('Users', on_delete=models.CASCADE,null=True,db_column='user_id', related_name='advertiser_users')
advertiser_id = models.ForeignKey('Advertisers', on_delete=models.CASCADE,null=True,db_column='advertiser_id', related_name='advertiser_users')
class Users(models.Model):
email = models.CharField(unique=True, max_length=100)
I want Id's, user ids and email of all advertisers.
Id's of all user:-
advertiser_ids = advertisers.objects.all() # can get id from here
find user_ids of advertiser_ids:
user_ids = AdvertiserUsers.objects.filter(advertiser_id__in=advertiser_ids) # can get user_id from here
find id and email using this query:
user_ids = Users.objects.filter(id__in=user_ids) # can get email from here
How to make it shorter like directly querying from Advertisers i will be able to get Users models email.
Thankyou in advance
You can filter with:
Users.objects.filter(advertiser_users__advertiser_id__isnull=False).distinct()
The .distinct() [Django-doc] will prevent returning the same Users multiple times.
You can annotate the User objects with the Advertisers primary key, etc:
from django.db.models import F
Users.objects.filter(advertiser_users__advertiser_id__isnull=False).annotate(
account_manager_id=F('advertiser_users__advertiser_id__account_manager_id'),
advertiser_id=F('advertiser_users__advertiser_id')
)
The Users objects that arise from this have a .email attribute (and the other attributes that belong to a Users object), together with a .account_manager_id and an .advertiser_id. That being said, this is probably not a good idea: the way you have modeled this right now, is that a Users object can relate to multiple Advertisers objects, so it makes not much sense to add these together.
You can for each user access the related Advertisers with:
myusers = Users.objects.filter(
advertiser_users__advertiser_id__isnull=False
).prefetch_related(
'advertiser_users',
'advertiser_users__advertiser_id'
).distinct()
for user in myusers:
print(f'{user.email}')
for advuser in user.advertiser_users.all():
print(f' {advuser.advertiser_user.pk}')
Note: normally a Django model is given a singular name, so User instead of Users.
Note: Normally one does not add a suffix _id to a ForeignKey field, since Django
will automatically add a "twin" field with an _id suffix. Therefore it should
be account_manager_id, instead of account_manager.
Advertisers.objects.all().values_list('id','account_manager_id','advertiser_users__user_id',advertiser_users__user_id__email)
I have an invoice object that has an account object inside it. When displaying the invoice to a user, I have the following object:
invoice : {
Number : 1234,
Account : { id: 12345,
name: "Test account"
}
}
When saving an invoice, the user can select the account from a drop down. In that case, all I really need is the id of that account so my object will look something like this:
invoice : {
Number : 1234,
AccountId : 12345
}
My question is: Do I need to create two different objects one for saving and another one for displaying the invoice? If not, how would you handle this?
Thanks!!
Create another property "AccountId" in same javascript object and delete unwanted property just before saving it.
invoice.AccountId = invoice.Account.id;
delete invoice['Account'];
I would like to store some information as follows (note, I'm not wedded to this data structure at all, but this shows you the underlying information I want to store):
{ user_id: 12345, page_id: 2, country: 'DE' }
In these records, user_id is a unique field, but the page_id is not.
I would like to translate this into a Redis data structure, and I would like to be able to run efficient searches as follows:
For user_id 12345, find the related country.
For page_id 2, find all related user_ids and their countries.
Is it actually possible to do this in Redis? If so, what data structures should I use, and how should I avoid the possibility of duplicating records when I insert them?
It sounds like you need two key types: a HASH key to store your user's data, and a LIST for each page that contains a list of related users. Below is an example of how this could work.
Load Data:
> RPUSH page:2:users 12345
> HMSET user:12345 country DE key2 value2
Pull Data:
# All users for page 2
> LRANGE page:2:users 0 -1
# All users for page 2 and their countries
> SORT page:2:users By nosort GET # GET user:*->country GET user:*->key2
Remove User From Page:
> LREM page:2:users 0 12345
Repeat GETs in the SORT to retrieve additional values for the user.
I hope this helps, let me know if there's anything you'd like clarified or if you need further assistance. I also recommend reading the commands list and documentation available at the redis web site, especially concerning the SORT operation.
Since user_id is unique and so does country, keep them in a simple key-value pair. Quering for a user is O(1) in such a case... Then, keep some Redis sets, with key the page_id and members all the user_ids..
I am sure there must be a simple way to do this, but I have been combing the manual and can't find it.
A user creates a new "course" model and in the same form adds a dynamic number of "student" models. Each student belongs to one course. So I receive the data to the controller roughly like this:
Array
(
[Course] => Array(name, etc. etc.),
[Student] => Array(
[0] => Array(student details, etc.),
[1] => Array(student 2 details, etc.))
)
Once the controller receives this, I save the Course data to create the new course. I now have the course unique ID from the database...how do I easily save the student data, adding the course_id automatically to each Student, without having to loop through all of them and adding the course_id manually?
Thanks!
If your model relationships are setup correctly, you can use saveAll().
Check the book on Saving your Data.
The title is a bit awkward but I couldn't found a better one. My problem is as follows:
I have several users stored as documents and I am storing several key-value-pairs or items (which have an id) for each document. Now, if I apply highlighting with hl.snippets=5 I can get the first 5 items. But every user could have several hundreds items, so
you will not get the most relevant 5 items. You will get the first 5 items ...
Another problem is that
the highlighted text won't contain the id and so retrieving additional information of the highlighted item text is ugly.
Example where items are emails:
user1 has item1 { text:"developers developers developers", id:1, title:"ms" }
item2 { text:"c# development", id:2, title:"nice!" }
...
item77 ...
user2 has item1 { text:"nice restaurant", id:3, title:"bla"}
item2 { text:"best cafe", id:4, title:"blup"}
...
item223 ...
Now if I use highlighting for the text field and query against "restaurant" I get user2 and the text nice <b>restaurant</b>. But how can I determine the id of the highlighted text to display e.g. the title of this item? And what happens if more relevant items are listed at the end of the item-list? Highlighting won't display those ...
So how can I find the best items of a documents with multiple such items?
I added my two findings as answers, but as I will point out each of them has its own drawbacks.
Could anyone point me to a better solution?
One of my rules of thumb for designing Solr schemas is: the document is what you will search for.
If you want to search for 'items', then these 'items' are your documents. How you store other stuff, like 'users', is secondary. So 'users' could be in another index like you mentioned, they could be "denormalized" (e.g. their information duplicated in each document), in a relational database, etc. depending on RDBMS availability, how many 'users' there are, how many fields these 'users' have, etc.
EDIT: now you explain that the 'items' are emails, and a possible search is 'restaurant X' and you want to find the best 'items' (emails). Therefore, the document is the email. The schema could be as simple as this: (id, title, text, user).
You could enable highlighting to get snippets of the 'text' or 'title' fields matching the 'restaurant X' query.
If you want to give the end-user information about the users that wrote about 'restaurant X', you could facet the 'user' field. Then the end-user would see that John wrote 10 emails about 'restaurant X' and Robert wrote 6. The end-user thinks "This John dude must know a lot about this restaurant" so he drills down into a search by 'restaurant x' with a filter query user:John
You could use use two indices: users->items as described in the question and an index with 'pure items' referencing back to the user.
Then you will need 2 queries (thats the reason I called the question '2d Search in Solr'):
query the user index => list of e.g. 10 users
query the items index for each user of the 1. step => best items
Assume the following example:
userA emails are "restaurant X is bad but restaurant X is cheap", "different topic", "different topicB" and
userB emails are "restaurant X is not nice", "revisited restaurant X and it was ok now", "again in restaurant X and I think it is the best".
Now I query the user index for "restaurant X" and the first user will be userB, which is what I want. If I would query only the item-index I would get the item1 of less relevant userA.
Drawbacks:
bad performance, because you will need one query against the user index and e.g. 10 more to get the most relevant items for each user.
maintaining two indices.
Update to avoid many queries I will try the following: using the user index to get some highlighted snippets and then offering a 'get relevant items'-button for every user which then triggers a query against the item index.
You can use the collapse patch and store each item as separate document linking back to the user.
The problem of that approach is that you won't get the most relevant user. Ie. the most relevant item is not necessarily from the most relevant user (because he can have several slightly less relevant items)
See the "Assume the following example:" part in my second answer.