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我正在使用 Kaminari 对选择不同记录的查询的一些结果进行分页。考虑以下控制器代码：

@things = Thing.joins... # create a complex query that produces duplicate results

# I want to select distinct results: this produces the correct results
@things = @things.select("DISTINCT things.*")

# when Kaminari calls count, it will run "SELECT COUNT(*)", instead of 
# "SELECT COUNT(DISTINCT things.*)" we will get the wrong count and extra pages
@things = @things.page(params[:page]).per(10)

我能想到的最好的解决方案是传递:distinct => true给count，就像在这个 pull request中一样，它被 Kaminari 的开发人员拒绝了。这个 SO question讨论了潜在的问题。这行代码是对count.

是否有任何解决方法可以为 Kaminari 提供不涉及修补 Kaminari 的正确计数？谢谢。

更新：

  • 使用名为“count”的范围是一个很好的建议，但在 ActiveRecord::Relation 上调用时不起作用。它在我的模型类上调用时有效，但这无济于事。
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2 回答 2

3

please refer to the following url.

https://github.com/amatsuda/kaminari/pull/77

https://github.com/tbeauvais/kaminari/commit/23695cbdc4ff1b9fa58c18d4a3c2f18e21451b8b but ,they faild on Rails 3.1.0.

For Rails 3.1.0, create Rails.root/initializers/kaminari_for_distinct.rb. And use the following code.

module Kaminari
  module ActiveRecordRelationMethods
    extend ActiveSupport::Concern
    module InstanceMethods
      def total_count #:nodoc:
        if distinct_column_name.nil?
          c = except(:offset, :limit).count
        else  
          c = except(:offset, :limit).count(distinct_column_name, :distinct => true)
        end
        # .group returns an OrderdHash that responds to #count
        c.respond_to?(:count) ? c.count : c
      end

      # Get the column name used in distinct query.
      # This could have been set on the Model class, or the ActiveRecord::Relation 
      def distinct_column_name
        @distinct_column || distinct_column
      end
    end
  end
end

module Kaminari
  module ConfigurationMethods
    extend ActiveSupport::Concern
    module ClassMethods

      # Set the name of the column to use during .count()
      # Setting this will cause call to count to use: count(:id, :distinct => true) for all the Models paged queries. 
      # Example:
      #   class User < ActiveRecord::Base
      #     use_distinct :id
      #   end
      def use_distinct(column)
        @distinct_column = column
      end

      # Returns the distinct column name set on the Model, or nil if not using distinct
      def distinct_column
        @distinct_column
      end
    end
  end
end


module Kaminari
  module PageScopeMethods
    extend ActiveSupport::Concern
    module InstanceMethods

      # Set the name of the column to use during .count()
      # Setting this will cause call to count to use: count(:id, :distinct => true)
      # Example: User.page(3).per(5).use_distinct(:id)
      def use_distinct(column)
        @distinct_column = column
        self
      end
    end
  end
end
于 2011-09-02T16:51:43.523 回答
0

我会建议模型的范围

不过，这可能会使事情变得混乱，所以你要小心

范围 :count, select("DISTINCT things.*")

更多信息请看这里

于 2011-07-14T20:15:09.677 回答