自定义方法顶部的rails gem will_paginate不起作用

Question

In my controller, my filter_with_params() method is causing a syntax error in postgres when I try and stack will_paginate on top of it.

In my controller I call:

@styles = Style.filter_with_params(params).paginate(:page => params[:page], :per_page => 6)

Model method:

class Style < ActiveRecord::Base

def self.filter_with_params(params)
    scoped = where("styles.item != ''")
    if params[:t]
      scoped = scoped.joins(:tags)
      scoped = scoped.select("distinct styles.*, count(*) AS count")
      scoped = scoped.where(tags: { name: params[:t] })
      scoped = scoped.group('styles.id')
      scoped = scoped.having("count(*) = #{params[:t].size}")
    end
    scoped
end

basically my filter method is looking for tags, and then i need to paginate on top of those results. Anyone with similar experience?

I'm using Rails 3 on this app

here is the postgres error

PG::Error: ERROR:  syntax error at or near "distinct" LINE 1: SELECT COUNT(*) AS count_all, distinct styles.*, count(*) AS...
                                  ^
: SELECT COUNT(*) AS count_all, distinct styles.*, count(*) AS count, styles.id AS styles_id FROM "styles" INNER JOIN "tagizations" ON "tagizations"."style_id" = "styles"."id" INNER JOIN "tags" ON "tags"."id" = "tagizations"."tag_id" WHERE "tags"."name" IN ('engagement') AND (styles.polenza_item != '') GROUP BY styles.id HAVING count(*) = 1

Answer 1

Your SQL has a problem. You need to say distinct clause before the count ('count(*) as count_all'). That is, once you remove the first call to the count function, it should work.

SELECT distinct styles.*, count(*) AS count, styles.id AS styles_id FROM "styles" INNER JOIN "tagizations" ON "tagizations"."style_id" = "styles"."id" ...

You can test your query in your rails console:

>> sql = "SELECT distinct styles.*, count(*) AS count, styles.id AS styles_id..."
>> a = ActiveRecord::Base.connection.execute(sql)
>> a[0]

Hope this helps.