I am having a problem with an association:
Battalion
:has_many soldiers
Soldiers
:has_many primaries
I need to do this
#bseniorleads=(#user.battalion.soldiers.find(:all, :conditions => ["seniorleader = ?", "Yes"]))
then
#seniorspouse=(#bseniorleads.primaries.find(:all, :conditions => ["relationship = ?", "Spouse"]
This gives me an undefined method for primaries, I assume because the bseniorleads is an array?
Basically I don't know how to do this they right way but I need to be able to query a group from one model that meets a condition and then take that result and find the people from another model that belong to them. Any ideas?
Thanks in advance.
You should be able to do something like this (assuming you only needed the #bseniorleads instance variable in the second query):
#senior_spouse = #user.battalion.soldiers.find(
:all,
:select => 'primaries.*',
:joins => [:primaries],
:conditions => ["seniorleader = ? and primaries.relationship = ?", "Yes", "Spouse"]
)
I haven't checked that yet, but I think it should get you pretty close.
You might want to check out these two rails guides, which certainly helped me better understand ActiveRecord associations and querying:
ActiveRecord Querying
ActiveRecord Associations
Related
I need to delete a lot of records at once and I need to do so based on a condition in another model that is related by a "belongs_to" relationship. I know I can loop through each checking for the condition, but this takes forever with my large record set because for each "belongs_to" it makes a separate query.
Here is an example. I have a "Product" model that "belongs_to" an "Artist" and lets say that artist has a property "is_disabled".
If I want to delete all products that belong to disabled artists, I would like to be able to do something like:
Product.delete_all(:joins => :artist, :conditions => ["artists.is_disabled = ?", true])
Is this possible? I have done this directly in SQL before, but not sure if it is possible to do through rails.
The problem is that delete_all discards all the join information (and rightly so). What you want to do is capture that as an inner select.
If you're using Rails 3 you can create a scope that will give you what you want:
class Product < ActiveRecord::Base
scope :with_disabled_artist, lambda {
where("product_id IN (#{select("product_id").joins(:artist).where("artist.is_disabled = TRUE").to_sql})")
}
end
You query call then becomes
Product.with_disabled_artist.delete_all
You can also use the same query inline but that's not very elegant (or self-documenting):
Product.where("product_id IN (#{Product.select("product_id").joins(:artist).where("artist.is_disabled = TRUE").to_sql})").delete_all
In Rails 4 (I tested on 4.2) you can almost do how OP originally wanted
Application.joins(:vacancy).where(vacancies: {status: 'draft'}).delete_all
will give
DELETE FROM `applications` WHERE `applications`.`id` IN (SELECT id FROM (SELECT `applications`.`id` FROM `applications` INNER JOIN `vacancies` ON `vacancies`.`id` = `applications`.`vacancy_id` WHERE `vacancies`.`status` = 'draft') __active_record_temp)
If you are using Rails 2 you can't do the above. An alternative is to use a joins clause in a find method and call delete on each item.
TellerLocationWidget.find(:all, :joins => [:widget, :teller_location],
:conditions => {:widgets => {:alt_id => params['alt_id']},
:retailer_locations => {:id => #teller_location.id}}).each do |loc|
loc.delete
end
I have this rails find that i need to get the id as well but if i put the id in the :select wont it effect the query and is there another way to get the id
#past_requests = Request.find_all_by_artist(name, :conditions => ["showdate < ?", Time.now], :select => "distinct venue, showdate")
#past_requests = Request.find_all_by_artist(name, :group => "venue, showdate")
code long for view. i'm remove your condition. sorry about this. Hope it'll helpful for you. :)
To be fair in cases where distinct returns a single row out of maybe 5 duplicates who's to say which id out of those 5 should be displayed in your result? I'm afraid what you are asking for is not practical. Maybe you misunderstand what distinct is used for ? Give us more info pls.
Newb question of the day:
I'm trying to select all the users with this condition, and then perform an action with each one :
User.find(:all).select { |u| u.organizations.count > 0} do |user|
Except, this isn't the right way to do this. Not entirely sure what the proper syntax is.
Any fellow rubyist offer a newb a hand?
To perform an action with each element of a collection use the each method, like this:
User.find(:all).select { |u| u.organizations.count > 0}.each do |user|
You'd probably be better folding the select into the query with:
User.find(:all, :conditions => "organization_id IS NOT NULL").each do |user|
This will only fetch the relevant results from the database so there should be less unnecessary data retrieved and thrown away.
EDIT:
As suggested in the comments, the following would be correct for a many-to-many relationship assuming a join model called memberships (where user has_many :organisations, :through => :membership)...
User.all(:joins => "inner join memberships on memberships.user_id = users.id")
How do I get a random record when using :group?
#paintings = Painting.all(:group => "user_id", :order => "created_at DESC")
This gives me the latest painting for each user. Now I would like to select a random painting from each user instead of the latest. The order of the paintings should still be the same, so that the user that have been the most active will get his/her random painting displayed first.
painting150 (user1)
painting200 (user2)
painting231 (user3)
Is this possible?
Best regards.
Asbjørn Morell.
This answer is specific to Rails, but since you are using ActiveRecord, I am assuming it should be fine.
unique_paintings = []
#paintings.group_by(&:user_id).each do |user_id, paintings|
unique_paintings << paintings[rand(paintings.size-1)]
end
unique_paintings.sort_by(&:created_at)
The group_by most certainly messes up the created_at sort you did in the query, so I did a sort_by as the last step. You might want to get rid of it in the query since you'll have to do it anyway here.
#painting = #paintings[rand(#paintings.size-1)]
(or paintings.count, dont know the right method yet)
Assuming you have MySQL, you can try:
#paintings = Painting.all(:group => "user_id", :order => "RAND()")
you could do something like this but it will suffer as your number of records grow
#paintings = Painting.find(:all, :order => 'RAND()').map{ |i| i.user_id }.uniq
Right now I have a table called Campaigns that has many Hits, if I call say:
Campaign.find(30).hits
Which takes 4 seconds, or 4213 ms.
If I call this instead:
campaign = Campaign.find(30)
campaign.hits.count
Does it still load all of the hits, then count? Or does it see I am counting and avoids loading all of the hits? (Which is currently 300,000+ rows).
I am trying to figure out a smart way to load/count my hits. I am thinking about adding a method to my Campaign.rb model, like:
def self.total_hits
find :first, :select => 'COUNT(id) as hits', :conditions => ["campaign_id = ?", self.id]
end
I know that query won't load from the hits table, but that is just an example of counting it from a self made query, apposed to Ruby on Rails doing this for me.
Would this memcache query be more effecient? (I have it running, but doesn't seem to be any better/faster/slower, just the same speed.)
def self.hits
Rails.cache.fetch("Campaign_Hits_#{self.campaign_id}", :expires_in => 40) {
find(:first, :select => 'COUNT(id) as hits', :conditions => ["campaign_id = ?", self.campaign_id]).hits
}
end
Any suggestions would be great!
How about:
Campaign.find(30).hits.count
You might also consider adding the following in hit.rb (assuming a one-to-many relationship between campaigns and hits).
belongs_to :campaign, :counter_cache => true
You then need a column in the campaigns table called hits_count. This will avoid hitting hits altogether if you're only getting the count.
You can check the API for the full rundown.
My ActiveRecord might be a little rusty, so forgive me if so, but IIRC Campaign.find(30).hits is at least two separate queries. How does Campaign.find(30, :include => [ :hits ]).hits do? That should perform a single query.