I have the following associations set up
class bookinghdr
belongs_to :agent
end
class bookingitem
belongs_to :bookinghdr, :include => agent
end
So I was expecting to be able to do the following:
named_scope :prepay, :include=>["bookinghdr"], :conditions => ["bookinghdr.agent.agenttype = 'PP'"]
and in my controller do:
b = Bookingitem.prepay
But that gives me a ActiveRecord::StatementInvalid: Mysql::Error: Unknown column 'bookinghdr.agent.agenttype'
However if I don't include the conditions clause then I get a recordset on which I can do:
b = Bookingitem.prepay
b[0].bookinghdr.agent.agenttype
without any error!
I don't want to have to get all the records and then iterate over them to find the ones whose agent has a 'PP# flag. I was hoping that AR would do that for me.
Anybody got any ideas on how to achieve this?
Your question shows that you have not yet fully understood how associations and named scopes work. Since I cannot tell from your question what parts aren't clear, I suggest you read the Association Basics guide at http://guides.rubyonrails.org/v2.3.11/association_basics.html. This should bring you up to speed regarding the concepts you want to implement. After you have read the guide it should all make sense.
Related
I have two models: Patient and CodeStatus.
CodeStatus belongs_to Patient, and Patient has_one CodeStatus
I am trying to query all patients where patient.code_status is nil. I was surprised to find that Patient.where(code_status: nil) does not work throwing: column patients.patient_id does not exist
I have already found this (fairly old) answer, but I find it difficult to believe that the best way to query this is via a long string of raw SQL. I would think that rails would include this helper like they do for many other associations. Does anyone know of a less verbose solution to this? Thanks in advance.
The problem is, that
patient.code_status
is not a column, but a method, added by Rails when you say
class Patient
has_one :code_status
end
Here is how you'd get all patients not associated with any code status:
Patient.includes(:code_status).where(code_statuses: { id: nil })
I've got a fairly complex sql query that I'm pretty sure I can't accomplish with ARel (Rails 3.0.10)
Check out the link, but it has a few joins and a where exists clause, and that I'm pretty sure is too complex for ARel.
My problem however is that, before this query was so complex, with ARel I could use includes to add other models that I needed to avoid n+1 issues. Now that I'm using find_by_sql, includes don't work. I still want to be able to fetch these records and attach them to my model instances, the way includes does, but I'm not quite sure how to achieve this.
Can someone point me in the right direction?
I haven't tried joining them in the same query yet. I'm just not sure how they would be mapped to objects (ie. if ActiveRecord would properly map them to the proper class)
I know that when using includes ActiveRecord actually makes a second query, then somehow attaches those rows to the corresponding instances from the original query. Can someone instruct me on how I might do this? Or do I need to join in the same query?
Let's pretend that the SQL really can't be reduced to Arel. Not everything can, and we happen to really really want to keep our custom find_by_sql but we also want to use includes.
Then preload_associations is your friend:
(Updated for Rails 3.1)
class Person
def self.custom_query
friends_and_family = find_by_sql("SELECT * FROM people")
# Rails 3.0 and lower use this:
# preload_associations(friends_and_family, [:car, :kids])
# Rails 3.1 and higher use this:
ActiveRecord::Associations::Preloader.new(friends_and_family, [:car, :kids]).run
friends_and_family
end
end
Note that the 3.1 method is much better, b/c you can apply the eager-loading at any time. Thus you can fetch the objects in your controller, and then just before rendering, you can check the format and eager-load more associations. That's what happens for me - html doens't need the eager loading, but the .json does.
That help?
I am pretty sure that you can do even the most complex queries with Arel. Maybe you are being over-skeptical about it.
Check these:
Rails 3: Arel for NOT EXISTS?
How to do "where exists" in Arel
#pedrorolo thanks for the heads up on that not exists arel query, helped me achieve what I needed. Here's the final solution (they key is the final .exists on the GroupChallenge query:
class GroupChallenge < ActiveRecord::Base
belongs_to :group
belongs_to :challenge
def self.challenges_for_contact(contact_id, group_id=nil)
group_challenges = GroupChallenge.arel_table
group_contacts = GroupContact.arel_table
challenges = Challenge.arel_table
groups = Group.arel_table
query = group_challenges.project(1).
join(group_contacts).on(group_contacts[:group_id].eq(group_challenges[:group_id])).
where(group_challenges[:challenge_id].eq(challenges[:id])).
where(group_challenges[:restrict_participants].eq(true)).
where(group_contacts[:contact_id].eq(contact_id))
query = query.join(groups).on(groups[:id].eq(group_challenges[:group_id])).where(groups[:id].eq(group_id)) if group_id
query
end
end
class Challenge < ActiveRecord::Base
def self.open_for_participant(contact_id, group_id = nil)
open.
joins("LEFT OUTER JOIN challenge_participants as cp ON challenges.id = cp.challenge_id AND cp.contact_id = #{contact_id.to_i}").
where(['cp.accepted != ? or cp.accepted IS NULL', false]).
where(GroupChallenge.challenges_for_contact(contact_id, group_id).exists.or(table[:open_to_all].eq(true)))
end
end
So, I tried to search for an example of how to do this, and I'm not sure I even know how to describe what I'm trying to do. I'm an utter noob when it comes to SQL, and I'm sure this is really basic but I'm totally lost:
I have a model, Photo, which has_many :tags, :through => :taggings. Tags have a name and an id.
I want to do something like: Photo.where( #tag_name in [array] )
... but like I said I have no idea how to write something like that, or what to search to see an example on Google.
Can anyone give me an example of that kind of query, and what it might be called?
Thanks!
Just tried this on a similar model of my own and seemed to work fine:
Photo.joins(:tags).where('tags.name' => ['herp','derp']).group(:id)
Also, here's a great resource on the AREL querying interface rails 3 uses, with information on these and other ActiveRecord calls related to querying.
So, as a twist on Brett's method, it turns out the following works without breaking PostgreSQL:
def self.tagged_with( string )
array = string.split(',').map{ |s| s.lstrip }
select('distinct photos.*').joins(:tags).where('tags.name' => array )
end
Problem solved! See this article for a great explanation as to why this is a better idea than 'group'.
Apologies for the long title, but this is bothering me. I'm new to Rails, so this is my first project. Rails 3.0.3.
In my model, a User may or may not have read many Entries; this is tracked in a model called ReadEntries. This many-to-one relationship is properly defined in the code, I think.
User.rb:
has_many :read_entries
Entry.rb:
has_many :read_entries
ReadEntry.rb:
belongs_to :entry
belongs_to :user
This table has to be populated at some point. If I try to do this:
user.read_entries.find_or_create_by_entry_id(entry.id, :read => false)
I get the error Unknown key(s): read. Leave out trying to set :read, and it works.
However, if I create the same row with this, it works:
ReadEntry.find_or_create_by_entry_id_and_user_id(entry.id, user.id, :read => false)
Logically, these methods should be identical, right? Thanks.
I've also had weird experiences with find_or_create. I would love it if it worked, but it seems inconsistent.
I'm currently having the same issue as you, and I think it may be due to calling find_or_create on an association as opposed to the model directly. Here's my example:
permission_assignments.find_or_create_by_role_id(:role_id => role_id, :is_allowed => false)
This works to create the assignment, except the "is_allowed" field gets set to it's default of "true". This code works for me (in the Permission model, hence the self reference)
PermissionAssignment.find_or_create_by_permission_id_and_role_id(:permission_id => self.id, :role_id => role_id, :is_allowed => false)
It's more verbose, unfortunately, but it works. The only problem that I still notice is that the object that is returned has no id assigned (the record does get created in the database, however, but if I wanted to update any more attributes I wouldn't be able to without the id). Don't know if that's a separate issue or not.
Rails 3.0.4 here with Postgres 8.4
You cannot pass in other fields like that as Rails will assume they are options for the find. Instead, you will need to make your method call longer:
user.read_entries.find_or_create_by_entry_id_and_read(entry.id, false)
Or alternatively use a shorter, custom syntax for that.
For your final example, my thoughts are that Rails will take the second argument and use that as options. Other than that, I am not sure.
I have a rails app (running on version 2.2.2) that has a model called Product. Product is in a has-and-belongs-to-many relationship with Feature. The problem is that I need have search functionality for the products. So I need to be able to search for products that have a similar name, and some other attributes. The tricky part is that the search must also return products that have the exact set of features indicated in the search form (this is represented by a bunch of checkboxes). The following code works, but it strikes me as rather inefficient:
#products = Product.find(:all, :conditions=>["home=? AND name LIKE ? AND made_by LIKE ? AND supplier LIKE ? AND ins LIKE ?",hme,'%'+opts[0]+'%','%'+opts[1]+'%','%'+opts[3]+'%','%'+opts[4]+'%'])
#see if any of these products have the correct features
if !params[:feature_ids].nil?
f = params[:feature_ids].collect{|i| i.to_i}
#products.delete_if {|x| x.feature_ids!=f}
end
I'm sorry that my grasp of rails/sql is so weak, but does anyone have any suggestions about how to improve the above code? Thanks so much!
First, i would recommend you to manually write a FeatureProduct model (and not use the default 'has_and_belongs_to_many')
EG
class FeatureProduct
belongs_to :feature
belongs_to :product
end
class Product
has_many :feature_products
has_many :features, :through => :feature_products
end
class Feature
has_many :feature_products
has_many :products, :through => :feature_products
end
For the search: You may find the gem SearchLogic to be exactly what you need. It has support for 'LIKE' conditions (it means that you can write in a more 'Rails way' your query). It also has support for performing a search with conditions on a related model (on your Feature model, to be more precise).
The solution would be something like:
search = Product.search
search.name_like = opt[0]
search.made_by_like = opt[1]
...
search.feature_products_id_equals = your_feature_ids
..
#product_list = search.all
There is also an excellent screencast explaining the use of this gem.
Good luck :)