My BookingGroup has_many Booking. Booking contains column category where the data can be "adult" or "child_infant" or child_normal.
Now I want to count all total %child% and display it in my index view table
I was'nt sure whether this could be done in one line or I have to use a scope, this is where I stucked.
BookingGroup model
def search_by_category
bookings.visible.map(&:category).inject(:+)
end
Assuming category is a string column, you should be able to count it like that :
bookings.visible.where("category LIKE ?", "child%").count
bookings.visible.where(category: ["child_infant", "child_normal"]).count
We can use LIKE just as in SQL with active record
In your BookingGroup model
def search_by_category
bookings.visible.where('category LIKE ?', '%child%').size
end
But, if you do so for many booking_groups, your code will have N+1 queries issue. You can use eager load in your controller
#booking_groups = BookingGroup.joins(:bookings).select('booking_groups.*', 'count(*) as total_bookings').where('bookings.category LIKE ?', '%child%').group(:id)
Then you can
#booking_groups.first.total_bookings
Related
I have a database query where I want to get an array of Users that are distinct for the set:
#range is a predefinded date range
#shift_list is a list of filtered shifts
def listing
Shift
.where(date: #range, shiftname: #shift_list)
.select(:user_id)
.distinct
.map { |id| User.find( id.user_id ) }
.sort
end
and I read somewhere that for readability, or isolating for testing, or code reuse, you could split this into seperate methods:
def listing
shiftlist
.select(:user_id)
.distinct
.map { |id| User.find( id.user_id ) }
.sort
end
def shift_list
Shift
.where(date: #range, shiftname: #shift_list)
end
So I rewrote this and some other code, and now the page takes 4 times as long to load.
My question is, does this type of method splitting cause the database to be hit twice? Or is it something that I did elsewhere?
And I'd love a suggestion to improve the efficiency of this code.
Further to the need to remove mapping from the code, this shift list is being created with the following code:
def _month_shift_list
Shift
.select(:shiftname)
.distinct
.where(date: #range)
.map {|x| x.shiftname }
end
My intention is to create an array of shiftnames as strings.
I am obviously missing some key understanding in database access, as this method is clearly creating part of the problem.
And I think I have found the solution to this with the following:
def month_shift_list
Shift.
.where(date: #range)
.pluck(:shiftname)
.uniq
end
Nope, the database will not be hit twice. The queries in both methods are lazy loaded. The issue you have with the slow page load times is because the map function now has to do multiple finds which translates to multiple SELECT from the DB. You can re-write your query to this:
def listing
User.
joins(:shift).
merge(Shift.where(date: #range, shiftname: #shift_list).
uniq.
sort
end
This has just one hit to the DB and will be much faster and should produce the same result as above.
The assumption here is that there is a has_one/has_many relationship on the User model for Shifts
class User < ActiveRecord::Base
has_one :shift
end
If you don't want to establish the has_one/has_many relationship on User, you can re-write it to:
def listing
User.
joins("INNER JOIN shifts on shifts.user_id = users.id").
merge(Shift.where(date: #range, shiftname: #shift_list).
uniq.
sort
end
ALTERNATIVE:
You can use 2 queries if you experience issues with using ActiveRecord#merge.
def listing
user_ids = Shift.where(date: #range, shiftname: #shift_list).uniq.pluck(:user_id).sort
User.find(user_ids)
end
I have two tables: Restaurant and Meal
restaurant has_many meals and meal belongs_to restaurant.
Hence each meal has a restaurant_id column.
I have a #meals_search variable in my controller that is a list of meals from a search of a user in a search bar.
I want to display the restaurants corresponding to the #meals_search.restaurant_id but so far I can't find the right ActiveRecord query.
For example, if #meals_search.pluck(:restaurant_id) is equal to [1,7,44,53], then I want to create a #restaurants variable that stores restaurants with id 1,7, 44 and 53.
I populate the #meals_search variable like this:
meals_controller.rb
#meals_search = #meals.search(params[:search])
model.meal.rb
belongs_to :restaurant
def self.search(search)
if search
where('name LIKE ?', "%#{search}%")
else
all
end
end
Any idea ?
If I understand your problem correctly, you simply need to do this:
#restaurants = Restaurant.where(id: #meals_search.pluck(:restaurant_id))
This uses ActiveRecord subset conditions.
The above query translates to something like:
SELECT * FROM Restaurant WHERE (restaurant.in IN (1,3,5))
If I understand your question correctly, you want something like this?
#restaurants = Restaurant.where(id: #meals_search.pluck(:restaurant_id))
You can also use map insted of pluck
#restaurants = Restaurant.where(id: #meals_search.map {|m| m.restaurant_id})
I have a model Category, which has_many Products, and a Product in turn has_many Categories. When a user searches for a Category, I'd like to return the products of the matching Categories without losing my Arel object. Here's what I have so far:
Category.where("upper(title) like ?", search_term.upcase).map {|category| category.products}.flatten
This does the trick of returning the products, but of course what I have is an array and not Arel. I can get as far as adding an :includes(:products) clause, so I do indeed get the products back but I still have them attached to their categories. How do I adjust my query so that all I get back is an Arel that only addresses products?
If it is products that you want then you should probably start with the Product object when you are searching. For example ,you could do it like this:
Product.joins(:categories).where("upper(categories.title) like ?", search_term.upcase)
The reason I use joins instead of includes is that joins will perform an INNER JOIN instead of LEFT OUTER JOIN which is what you need to only return the products that are actually associated with the found categories.
To make it a little more elegant you could wrap it all up in a scope in your Product model like this:
# In Product.rb
scope :in_categories_like, Proc.new{ |search_term|
joins(:categories).where("upper(categories.title) like ?", search_term.upcase)
}
# In use
#products = Product.in_categories_like(params[:search_term])
I want to build a rails request with 2 models.
I think it's quite simple, but I don't want to do a loop myself.
I'm in my country model:
def self.find_for_user(user_id)
wines = Wine.where("user_id = ?", user_id).group(:country_id)
where("countries.id IN ?", wines.map())
end
I want to get all countries depending the first request (the wines grouped by countries, I just need the countries)
I think I can do this in a single line where I put map() or another instruction. I just need to get all country_id fields for wines.
Thanks.
Assuming that you've got an association set up between wines and country (ie. has_many :wines in country.rb), I think this is what you're looking for:
def self.find_for_user(user_id)
joins(:wines).where('wines.user_id = ?', user_id).uniq
end
If all you want is all countries that have wine for a specific user, you can do that in SQL:
where("countries.id in (select country_id from wines where wines.user_id = ?)", user_id)
Looking for a simple method utilizing active record to grab data from two models, combine the data, and then sort the combined output by created_at.
For example:
assume two models, Comment & Like both belongs_to User
return a combined list of #user's comments and likes sorted by date
I know I can do this in SQL but I'd really like an active record solution.
Thanks!
I believe it should be as simple as:
combined_sorted = (User.comments + User.likes).sort{|a,b| a.created_at <=> b.created_at }
How about something like (untested):
class User < ActiveRecord::Base
scope :activities_by_date, :joins(:comments).joins(:likes).order("created_at desc")
end
Then you can do #user.activities_by_date and let the db do all the work