I am creating a website that allows users to evaluate their coworkers. My boss would like the averages to be displayed from best to worst on a static page that she can print and hang up in our store, so the employees can see their results compared to other employees. I have been searching for awhile now on how to easily sort a column. I found a Railscast on sorting columns, but it seems a lot more detailed than I truly need. I found the order API, but I don't think I'm implementing it the way I need to. I am hoping that maybe there is a one-liner that can help me solve this problem, such as:
#user = User.all.order(average: :asc)
Where I can load a static page that prints the user's name and their score. Thank you in advance!
Have you tried that code of yours? It should do exactly what you're asking except from lowest score to highest score.
You could simplify it a little and sort from highest to lowest by doing:
#users = User.order(average: :desc)
Like MarsAtomic said, this assumes that you actually have a column in your users table called average. If not we need more information on how your database is set up.
Related
I am using Rails 4. I have a Room model with hour_price day_price and week_price attributes.
On the index, users are able to enter different times and dates they would like to stay in a room. Based on these values, I have a helper method that then calculates the total price it would cost them using the price attributes mentioned above.
My question is what is the best way to sort through the rooms and order them least to greatest (in terms of price). Having a hard time figuring out the best way to do this, especially when considering the price value is calculated by a helper and isn't stored in the database.
You could load all of them and do an array sort as is suggested here, and here. Though that would not scale well, but if you've already filtered by the rooms that are available this might be sufficient.
You might be able to push it back to the database by building a custom sql order by.
Rooms.order("(#{days} * day_price) asc")
sorry if it's duplicate, I've been looking for something similar before posting, but no success.
So basically I need an up/down rating system ( it's very similar to the one here on stackoverflow ).
I have 6 rateable models, so polymorphic association seem to be the best option.
But since this table will probably hold a solid number of records, won't it take too much time to get the item rating ( upvotes_count - downvotes_count )?
I actually though about adding a new row to each and every rateable model, something like current_rating_value. So that this value will be changed every time the rating object will be created/destroyed.
Could you please advice, what might be a better option in this case? Extra UPDATE call to change the current_rating_value or an extra SELECT(SUM...) call to calculate it?
Depending on how much traffic you get loading these models it could tax resources more then desired. I've ended up using acts_as_votable gem in my projects. Its very easy to make a model votable and it also caches the data which is also awesome.
for the long-term performance, you should add something like current_rating_value into every ratable model. Everytime there is new rate, just update this field.
Otherwise, it will be very harmful to performance when you have to calculate the rating everytime.
EDIT: I know it's been over a year, but I finally got something new to this problem. To see an update for this look at this question: Rails 3 user matching-algorithm to SQL Query (COMPLICATED)
I'm working on a site where users are matched based on answered questions.
The match percentage is calculated each time a user, for example, visits another users profile page. So the matching percentage is not stored in the database and is recalculated all the time.
Now I want to build in a search where users can search for their best match.
The question I have is, what is the most efficient way to do this?
What if I have 50k users and I have to list them ordered by match percentages. Do I have to calculate each matching percentage between one and the other 50k users and then create a list out of that? Sounds kind of inefficient to me. Wouldn't that slow down the app drastically?
I hope someone can help me with this, because this gives me kind of a headache.
EDIT:
To clear things up a bit, here is my database model for user, questions, answers, user_answers and accepted_answers:
Tables:
Users(:id, :username, etc.)
Questions(:id, :text)
Answers(:id, :question_id, :text)
UserAnswers(:id, :user_id, :question_id, :answer_id, :importance)
AcceptedAnswers(:id, :user_answer_id, :answer_id)
Questions <-> Answers: one-to-many
Questions <-> UserAnswers: one-to-many
Users <-> UserAnswers: one-to-many
UserAnswers <-> AcceptableAnswers: one-to-many
So there is a list of Questions(with possible answers to this question) and Users give their "UserAnswers" to those questions, assign how important that question is to them and what answers they accept from other users.
Then if you take User1 and User2, you look for common answered questions, so UserAnswers where the question_id is the same. They have 10 questions in common. User1 gave the importance value 10 to the first five questions and the importance value 20 to the other five. User 2 gave acceptable answers to two 20 value and three 10 value questions. A total of 70 points. The highest reachable pointscore is of course 20x5 + 10x5... So User2 reached 70/150 * 100 = 46,66% ... The same thing is done the other way around for how much User1 reached of User2's assigned points to those questions. Those 2 percentages are then combined through the geometric mean: sqrt of percentage1 * percentage2 ... this gives the final match percentage
#Wassem's answer seems on spot to your problem. I would also suggest you take an approach where percentages are updated on new answers and new accepted answers.
I have created a db only solution(gist), which would work but has an additional complexity of an intermediate table.
Ideally you should create two more tables, one for importance and another for percentage matches. You should create/insert/delete rows in these tables when user assigns/updates importance to an answer or marks some answer as acceptable. You can also leverage delayed_job or rescue to update the tables in background on the particular actions.
You may need to run the sqls once in while to sync up the data in the two new tables as there can be inconsistencies arising due to concurrency and also due to ordering of update actions in certain cases.
Updates on a accepted answer should be straight forward as you only need to update one pair. But in case somebody assigns importance to a question, there can be a lot calculations and a lot of percentages might need updation. To avoid this you might chose to only maintain the table with sums of importance for each pair, update it when required and calculate actual percentages on the fly(in db off-course).
I suggest you keep the match percentage of all the users in your database. Create a table matches that has match percentage for a pair of users. You do not need to save match percentage for all the pairs of users in your database. A valid match percentage is calculated for two users only when any one of have them has accepted an answer from other user. Most of the users will not accept the answers of most of other users.
I will suggest you to calculate and save the match percentage not at the time when a user visits another users profile. But when a user accepts another users answers. This will make sure that you do not make any unnecessary calculation and match percentage for a pair of users is always fresh.
I am having a problem implementing a special kind of search for my Rails application. I am working on an achievement system where you can search for a set of users in a search form (e.g., the query being "Ross, Adam, Jake") and it returns all of the common achievements that the users have unlocked (e.g., if users Ross, Adam, and Jake all had an achievement named "You are winner!"). I have three tables, one for achievements, one for users, and a join table. We have tested the associations and such, so we know that works.
My first idea was to put the search terms in an array and get the search results for each item in the array and place them into respective "search result arrays". Then, I was thinking to go through each item in search result array 1 to see if it appears in both of the other result arrays. The objects that appear in all three of the search result arrays would be returned and displayed on a page.
Is there an easy way to implement this without writing a bunch of my own code? Are there some functions I should know about? Any help will be appreciated!
Well, both Ransack and it's predecessor (MetaSearch) are useful gems for creating complex search forms.
In general I think you want to do something like select distinct achievement ids for user ids in an array. Off the top of my head I'm not quite sure how you should write it... others may know.
Look at the documentation on MetaSearch (more established) and see if you see a pattern that fits, if not check Ransack (more advanced).
You can use some autocomplete plugin for user names and convert the names to ids on the fly, that way you won't have to deal with converting user names to ids in backend later.
For common achievements, if a user can have a achievement only once, aggregating the results in join table and counting the results with achievement ids would be the way to go.
You can provide more details for a more detailed answer. :)
You can use Sunspot which is allows easy solr integration with Ruby and Rails
I will give an example:
Books.find(THIS_FIND_MAY_GET_MORE_THAN_ONE_BOOK).pages.all
I am expecting a set of pages... Every page returned should be contained in at least one book. Otherwise it shouldn't be in the set. How can I get such a set?
My intuitive idea was looping over the books and then add every time, but i guess there may be a faster way (databasewise), as I am not interested in the books. I don't want to introduce further database links as I think they may lead to a inconsistent database.
Any suggestions? Thanks!
To get all of the pages for each book...
books=Books.find(:all)
...will give you an array of books. Then you can loop over every book to get its pages...
books.each do |book|
puts book.pages
end
This assumes you have setup a relation between books and pages where each book has many pages and each page belongs to a book.
I'm not that sure on what you really want to do, but since you want pages instead of books, why not use Page.find_by_book_id or by whatever else you want and pass an array with the book ids for instance.
If this is not what you really want, could you please provide some more information on what you want to achieve ? Maybe a scope can work for you, maybe you can write some more info so that i can help you any further.
I guess this is what you want:
pages = Page.where("book_id is not NULL")