Is it possible to group by distance using the geokit-rails gem for ActiveRecord?
Say I have 10,000 users and I want to know how many are 1 mile, 2 miles... 100 miles from a point. How can I do that in as few queries as possible?
Doing something like this kills performance obviously:
(1..100).map { |i| User.count(:within => i, :origin => location) }
Is there someway to do:
User.count(:within => 100, :origin => location, :group => "distance / 100") # some sort of math perhaps
Any point in the right direction would be awesome! Some sort of way to chunk the records in one db call by a range.
I think the following db call will do what you ask for:
result = User.all(:select => "ROUND(distance / 100) AS distance, COUNT(*) AS user_count",
:group => "ROUND(id / 100)")
Since this will not load an actual user instance, you have to specify in the select what data you want to access. Then you can loop through the result like this:
<% result.each do |group| %>
<p>Distance: <%= group.distance %>, Number of users: <%= group.user_count %></p>
<% end %>
Related
I have a form to record sports times : I need minutes, seconds and hundredths of second, i.e. 1:31.43 --- I don't need the hour.
In my form I use :
<%= f.time_select :perf_time, {:discard_hour => true, :default => {:minute => '00', :second => '00'}, :include_seconds => true} %>
This displays 2 select pull-downs, one for minutes and one for seconds.
I have added a separate field for hundredths of second (type Integer):
<%= f.number_field :perf_time_cents, :in => 0..999 %>
Now I'd like to use the method .change()in my helper to change add/change the microseconds to perf_time. Here's my code, but it does not do anything.
before_save :set_perf_time
def set_perf_time
self.perf_time.change(usec: (self.perf_time_cents * 10))
end
There is no option for milliseconds in time_select because a combobox with 1000 possible values would not be user friendly.
You could use instead a separate text field for the number of milliseconds, with the HTML5 type number:
<%= f.number_field :perf_time_millis, :in => 0..999 %>
In the controller, use both the values in the selects and the text input field to get the full time in millis:
time_in_millis = params[:perf_time_millis].to_i + 1000 * (params["perf_time(5i)"].to_i * 60 + params["perf_time(6i)"].to_i))
I've been trying for a while to find the best way of querying for the desired result, but I always end up failing at some poing in the query.
Simplified database structure:
User:
id (integer)
first_name (string)
last_name (string)
CourseType:
title (string)
slug (string)
Course:
belongs_to :user
belongs_to :course_type
week (integer)
sold (float)
My controller is calling a scope:
#users = User.sales_results(week)
And here's the scope in my model:
scope :sales_results, lambda { |week|
joins(:courses => [:course_type])
.select("
users.id, users.first_name, users.last_name,
SUM(courses.sold) as total_sold,
COUNT(courses) as num_classes
")
.where("courses.week = ?", week)
.group('users.id')
}
This works fine, and I can use it in my template to show the total amount sold. Although I also want to show a second column where the value sold for some specific types of courses are summed up in. Something like this:
<% #users.each do |user| %>
<%= user.total_sold %>
<%= user.total_sold.where("course_types.slug IN ('H', 'S')") # not possible, but similar to what I desire %>
<% end %>
Update
I ended up adding another scope
scope :sales_results_for_types, lambda { |week, types|
sales_results(week).except(:group).where("course_types.slug IN (?)", types)
.group('users.id')
}
Then calling both scopes in my controller
#users = User.sales_results(...)
#users_filtered = User.sales_results_for_types(...)
Lastly iterating both results at the same time
<% #users.zip(#users_filtered).each do |user, filtered| %>
<%= filtered.total_sold %>
<%= user.total_sold %>
Until I figure out something better. Thanks guys for leading me on the right track.
If you are ok with having another query, you can use this
user.joins(courses: :course_type).sum(:sold, group: 'course_types.slug')
which will give you a hash where the keys are the slugs, and the values are the sums.
I have a Rails app that is using the simple_form gem. I have two models that are related, trades and stocks. In the form for trades, I want users to be able to enter their stock ticker symbol in a text field. Currently, I'm using the association function which renders a select box. The problem is that I want a text field instead since I have about a thousand stocks to choose from.
Is there a way I can do this (with or without Simple Form)?
the models:
class Trade < ActiveRecord::Base
belongs_to :stock
end
class Stock < ActiveRecord::Base
has_many :trades
end
the form on trades#new
<%= simple_form_for(#trade) do |f| %>
<%= f.association :stock %>
<% end %>
You should be able to just use this syntax:
<%= f.input :stock_id, :label => 'Enter your ticker:' %>
The problem here is that the user will not know what :stock_id is, as it's a reference to one of your many Stock objects.
So you probably want to implement a simple jquery autocomplete interface that returns a list of stocks like so:
[{:ticker => 'AAPL', :name => 'Apple Inc', :id => 1}, {:ticker => 'IBM', :name => 'International Business Machines', :id => 2}, etc ]
You can then display something like this as autocomplete results:
AAPL - Apple Inc
IBM - International Business Machines
and allow the user to select the one they are looking for. Behind the scenes you capture the :id and use that as your associated :stock_id.
You will need to add a stocks_controller action that takes a string and looks up Stocks based on a partial ticker and returns a max-number of stocks like 20.
def search
ticker_query = "%#{params[:ticker]}%"
stocks = Stock.where('ticker LIKE ?', ticker_query).limit(20)
render :json => stocks
end
I am finishing up my first RoR project, and am working on a leaderboard system that shows the number of points users have accrued for correctly answering quiz questions.
I am getting all of the users that have answered at least one question correct, grouping them by user_id, and displaying them in descending order by most correct using this:
#users = Point.find(:all,
:group => 'user_id',
:order => 'correct DESC', :conditions => { :correct => "yes"})
In my view, I am using this to iterate through the results:
<% #users.each_with_index do |user, index| %>
However, I am not able to get the number of correct answers per user. I tried:
user.count
but that doesn't work. How do I get the number of items per group?
You're on the right track. Seems like you would be better off using the all command with the count condition within it as opposed to the count command. Something like this:
Point.all(:select => 'user_id, count(id) as point_count', :group => :user_id, :conditions => { :correct => 'yes' }, :order => 'point_count desc', :limit => 10)
This will return 10 limited Point objects with a user_id attribute (so you can still access the user relationship), and a point_count attribute with the number of correct points said user has obtained.
Note: you could change the limit to be however many users you wanted to display in your leaderboard. This example would return 10.
It might make more sense to have your code look like this:
#points = Point.all(:select => 'user_id, count(id) as point_count', :group => :user_id, :conditions => { :correct => 'yes' }, :order => 'point_count desc', :limit => 10)
And as I said in a comment below, you could iterate through them by doing something like this (this would assume that your User model has a name attribute):
<table>
<% #points.each do |point| %>
<tr>
<td><%= point.user.name %></td>
<td><%= point.point_count %></td>
</tr>
<% end %>
</table>
I think the problem may be that you think you're getting an Array back, but you actually get a Hash back.
Try doing:
p #users
(which is equivalent to puts #users.inspect). You'll probably see it's more so something like:
{ "1" => [UserObject, UserObject], "2" => `[UserObject] }
You can even do p #users.class and you'll see it's not an array.
When you loop with a .each_with_index on a Hash, you need to do:
#users.each_with_index do |(key, value), index|
Then you can do #users[key].count or value.count.
Figured out how to get the correct count:
#users = Point.count(:group => :user_id, :conditions => { :correct => "yes"})
The most simple way should be:
#user.points.where(:correct => "yes").count
Though this will only work if have defined your associations in the user and point model like
class User < ActiveRecord::Base
has_many :points
class Point < ActiveRecord::Base
belongs_to :user
(personally I would have used a bool flag (smallint) instead of string for the "correct" column.
I have this bit of code and I get an empty object.
#results = PollRoles.find(
:all,
:select => 'option_id, count(*) count',
:group => 'option_id',
:conditions => ["poll_id = ?", #poll.id])
Is this the correct way of writing the query? I want a collection of records that have an option id and the number of times that option id is found in the PollRoles model.
EDIT: This is how I''m iterating through the results:
<% #results.each do |result| %>
<% #option = Option.find_by_id(result.option_id) %>
<%= #option.question %> <%= result.count %>
<% end %>
What do you get with this:
PollRoles.find(:all,:conditions=>["poll_id = ?",#poll.id]).collect{|p| p.option_id}
You want to use this function to do things like this
PollRoles.count(:all, :group => 'option_id') should return a hash mapping every option_id with the number of records that matched it.