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golgote/Article.rb

Forked from otobrglez/Article.rb
Last active August 29, 2015 14:12
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  1. @otobrglez otobrglez created this gist Jul 12, 2011.
    39 changes: 39 additions & 0 deletions Article.rb
    View file
    Original file line number Diff line number Diff line change
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    # This method finds related articles using Jaccard index (optimized for PostgreSQL).
    # More info: http://en.wikipedia.org/wiki/Jaccard_index

    class Article < ActiveRecord::Base

    def related(limit=10)
    Article.find_by_sql(%Q{
    SELECT
    a.*,
    ( SELECT array_agg(t.name) FROM taggings tg, tags t
    WHERE tg.taggable_id = a.id AND tg.tag_id = t.id
    ) as tags,
    ((SELECT COUNT(*) FROM
    ((SELECT t.name FROM taggings tg, tags t
    WHERE tg.taggable_id = a.id AND tg.tag_id = t.id
    ) INTERSECT
    (SELECT t_2.name FROM taggings tg_2, tags t_2
    WHERE tg_2.taggable_id = #{self.id} AND tg_2.tag_id = t_2.id
    )) as intersection
    )::float /
    (SELECT COUNT(*) FROM
    ((SELECT t.name FROM taggings tg, tags t
    WHERE tg.taggable_id = a.id AND tg.tag_id = t.id
    ) UNION
    (SELECT t_2.name FROM taggings tg_2, tags t_2
    WHERE tg_2.taggable_id = #{self.id} AND tg_2.tag_id = t_2.id
    )) as union_total
    )::float) as score
    FROM
    articles a
    WHERE
    a.published = 1 AND
    a.id != #{self.id}
    ORDER BY score DESC, a.created_at DESC
    LIMIT #{limit}
    })
    end

    end