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POOptimizing daily ranking tabulation
 

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  1. POOptimizing daily ranking tabulation
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    <p>Each Poem as two Votes, one as poem_id, other_poem_id, wins &amp; the second record which is the inverse of the first. Maybe there is a better way, but I'm trying to find the poems with the highest win percent over a period of time. It's confusing because of the double records for each comparison. Should I add another table, Results, which has a comparison_id for the two Vote records?</p> <pre><code>Here is a sample poem_id:1 other_poem_id:2 wins:3 poem_id:2 other_poem_id:1 wins:3 so it is 50% rather than a running tally scope :recent, lambda { { :joins =&gt; "JOIN votes ON votes.poem_id = poems.id", :conditions =&gt; ["poems.created_at &gt; ?", 8.days.ago], :order =&gt; "votes.wins DESC", :limit =&gt; 10 } } </code></pre> <blockquote> <p>ActiveRecord::StatementInvalid: SQLite3::SQLException: ambiguous column name: created_at: SELECT<br> "poems".* FROM "poems" JOIN votes ON votes.poem_id = poems.id WHERE (created_at > '2010-02-12 15:12:35.764252') ORDER BY wins DESC LIMIT 10</p> </blockquote> <p>edit: I changed the schema, here is what I'm working with now... <br /> the following is a model keeping track of rankings for poems. I just wrote this 1st draft yesterday. It seems a bit clunky, but I don't know how to improve it just yet. DailyRanking.tabulate will be called every night by cron. (following the model is the schema for the Comparison.)</p> <pre><code># == Schema Information # Schema version: 20100221120442 # # Table name: daily_rankings # # id :integer not null, primary key # poem_id :integer # rank :integer # percentile :integer # wins :integer # losses :integer # draws :integer # comparisons :integer # created_at :datetime # updated_at :datetime # class DailyRanking &lt; ActiveRecord::Base belongs_to :poem class &lt;&lt; self def tabulate # 1. get all comparisons over the past 24 hours comparisons = Comparison.day.all # 2. collect poem id for each time it wins # TODO make hash of "poem_id" =&gt; {:wins =&gt; a, :losses =&gt; b, :draws =&gt; c} a, results = 0, [] while a &lt; comparisons.size c = comparisons[a] if c.poem1_id == c.winner_id results &lt;&lt; c.poem1_id elsif c.poem2_id == c.winner_id results &lt;&lt; c.poem2_id end a += 1 end # 3. presort by poem count a, unsorted_wins = 0, [] until results.empty? unsorted_wins &lt;&lt; [results.first, results.count(results.first)] results.delete(results.first) end # 4. sort by win count sorted_wins = unsorted_wins.sort { |a, b| b[1] &lt;=&gt; a[1] } # 5. repeat for losses a, results = 0, [] while a &lt; comparisons.size c = comparisons[a] if c.poem1_id == c.loser_id results &lt;&lt; c.poem1_id elsif c.poem2_id == c.loser_id results &lt;&lt; c.poem2_id end a += 1 end unsorted_losses = [] until results.empty? unsorted_losses &lt;&lt; [results.first, results.count(results.first)] results.delete(results.first) end sorted_losses = unsorted_losses.sort { |a, b| b[1] &lt;=&gt; a[1] } # 6. sort wins v losses # a. sort wins[poem] v losses[poem] # b. get poem and pct wins for wins[poem] # c. delete wins[poem] and losses[poem] # repeat unsorted_results, a = [], 0 while a &lt; sorted_wins.size poem_id = sorted_wins[a][0] wins = sorted_wins[a][1] losses = sorted_losses.select do |item| item.second if item.first == poem_id end.compact.first.second unsorted_results &lt;&lt; [ poem_id, wins / (wins + losses).to_f ] a += 1 end # 7. sort by pct sorted_results = unsorted_results.sort { |a, b| b[1] &lt;=&gt; a[1] } # 8. persist rankings sorted_results.each_with_index do |result, index| ranking = find_or_create_by_rank(index + 1) ranking.poem_id = result.first ranking.save! end end end end # == Schema Information # Schema version: 20100221120442 # # Table name: comparisons # # id :integer not null, primary key # poem1_id :integer # poem2_id :integer # response :string(4) default("none"), not null # winner_id :integer # loser_id :integer # user_id :integer # session_id :integer # ip :string(15) # created_at :datetime # updated_at :datetime # class Comparison &lt; ActiveRecord::Base scope :day, lambda { { :conditions =&gt; ["created_at &gt; ?", 1.day.ago] } } end </code></pre>
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