Error when combining search scopes

Question

I have a web-service that allows clients to search for articles with query parameters.It works fine if only one parameter is included but fails if I combine search_query and category. This is based on Comfortable_Mexican_Sofa where for_category is found. Even if I remove the order statement i get this error.

error

PG::InvalidColumnReference: ERROR: for SELECT DISTINCT, ORDER BY expressions must appear in select list LINE 1: ...ms_categories"."label" = 'Company News' ORDER BY pg_search_... ^ : SELECT DISTINCT "comfy_cms_pages".* FROM "comfy_cms_pages" INNER JOIN "comfy_cms_categorizations" ON "comfy_cms_categorizations"."categorized_id" = "comfy_cms_pages"."id" AND "comfy_cms_categorizations"."categorized_type" = $1 INNER JOIN "comfy_cms_categories" ON "comfy_cms_categories"."id" = "comfy_cms_categorizations"."category_id" INNER JOIN (SELECT "comfy_cms_pages"."id" AS pg_search_id, (ts_rank((to_tsvector('simple', coalesce("comfy_cms_pages"."content_cache"::text, '')) || to_tsvector('simple', coalesce("comfy_cms_pages"."label"::text, ''))), (to_tsquery('simple', ''' ' || 'austin' || ' ''' || ':')), 0)) AS rank FROM "comfy_cms_pages" WHERE (((to_tsvector('simple', coalesce("comfy_cms_pages"."content_cache"::text, '')) || to_tsvector('simple', coalesce("comfy_cms_pages"."label"::text, ''))) @@ (to_tsquery('simple', ''' ' || 'austin' || ' ''' || ':'))))) pg_search_comfy_cms_pages ON "comfy_cms_pages"."id" = pg_search_comfy_cms_pages.pg_search_id WHERE (layout_id = '1' AND is_published = 't') AND "comfy_cms_categories"."label" = 'Company News' ORDER BY pg_search_comfy_cms_pages.rank DESC, "comfy_cms_pages"."id" ASC, "comfy_cms_pages"."created_at" DESC

app/models/article.rb

class Article < Comfy::Cms::Page
  cms_is_categorized
  include PgSearch


  pg_search_scope :search_by_keywords, against: [:content_cache, :label], using: { tsearch: { any_word: true, prefix: true } }

app/commands/search_articles_command.rb

class SearchArticlesCommand
  def initialize(params = {})
    @since = params[:since_date]
    @keys = params[:search_query]
    @category = params[:category]
  end

  def execute
    Article.unscoped do
      query = if @since.present?
                Article.article.since_date(@since)
              else
                Article.published_article
              end
      query = query.for_category(@category) if @category.present?
      query = query.search_by_keywords(@keys) if @keys.present?
      query.where('').order(created_at: :desc)
    end
  end
end

comfortable-mexican-sofa/lib/comfortable_mexican_sofa/extensions/is_categorized.rb

module ComfortableMexicanSofa::IsCategorized

  def self.included(base)
    base.send :extend, ClassMethods
  end

  module ClassMethods
    def cms_is_categorized
      include ComfortableMexicanSofa::IsCategorized::InstanceMethods

      has_many :categorizations,
        :as         => :categorized,
        :class_name => 'Comfy::Cms::Categorization',
        :dependent  => :destroy
      has_many :categories,
        :through    => :categorizations,
        :class_name => 'Comfy::Cms::Category'

      attr_accessor :category_ids

      after_save :sync_categories

      scope :for_category, lambda { |*categories|
        if (categories = [categories].flatten.compact).present?
          self.distinct.
            joins(:categorizations => :category).
            where('comfy_cms_categories.label' => categories)
        end
      }
    end
  end

  module InstanceMethods
    def sync_categories
      (self.category_ids || {}).each do |category_id, flag|
        case flag.to_i
        when 1
          if category = Comfy::Cms::Category.find_by_id(category_id)
            category.categorizations.create(:categorized => self)
          end
        when 0
          self.categorizations.where(:category_id => category_id).destroy_all
        end
      end
    end
  end
end

ActiveRecord::Base.send :include, ComfortableMexicanSofa::IsCategorized

Updated Error

PG::SyntaxError: ERROR:  syntax error at or near "."
LINE 4: ...e = 'Class' AND categorized_id = 'comfy_cms_pages'.'id' AND ...
                                                             ^
: SELECT "comfy_cms_pages".* FROM "comfy_cms_pages" INNER JOIN (SELECT "comfy_cms_pages"."id" AS pg_search_id, (ts_rank((to_tsvector('simple', coalesce("comfy_cms_pages"."content_cache"::text, '')) || to_tsvector('simple', coalesce("comfy_cms_pages"."label"::text, ''))), (to_tsquery('simple', ''' ' || 'austin' || ' ''' || ':*')), 0)) AS rank FROM "comfy_cms_pages" WHERE (((to_tsvector('simple', coalesce("comfy_cms_pages"."content_cache"::text, '')) || to_tsvector('simple', coalesce("comfy_cms_pages"."label"::text, ''))) @@ (to_tsquery('simple', ''' ' || 'austin' || ' ''' || ':*'))))) pg_search_comfy_cms_pages ON "comfy_cms_pages"."id" = pg_search_comfy_cms_pages.pg_search_id WHERE "comfy_cms_pages"."layout_id" = $1 AND "comfy_cms_pages"."is_published" = $2 AND (
        EXISTS (
          SELECT 1 FROM categorizations
          WHERE categorized_type = 'Class' AND categorized_id = 'comfy_cms_pages'.'id' AND category_id IN (2)
        ))  ORDER BY pg_search_comfy_cms_pages.rank DESC, "comfy_cms_pages"."id" ASC

working solution but not a scope and have to be careful of order its being called

  def self.for_category(_category)
    Comfy::Cms::Categorization.includes(:category).references(:category).select(:categorized).pluck(:categorized_id)
    find(ids)
  end

Answer 1

I think it's best to override for_category built-in filter of your CMS. Too many joins in that query.

Override for_category like this:

scope :for_category, lambda { |*categories|
  if (categories = [categories].flatten.compact).present?
    self_ids = "{connection.quote_table_name(self.table_name)}.#{connection.quote_column_name(self.primary_key)}"
    self.where(
      "EXISTS (" +
        Comfy::Cms::Categorization.select('1').
          where(categorized_type: self.name).
          where('categorized_id' => self_ids).
          where(category_id: Comfy::Cms::Category.where(label: categories).pluck(:id)).to_sql +
      ")"
    )
  end
}

More on SQL EXISTS usage in Rails you can read in my Rails: SQL EXISTS brief how-to.

More on why you bump into that error you can read in question and answer here.

Specifically, pg_search wants order your results by rank. And for_category wants to select distinct fields of Article only, and doesn't care about search rank. Changing its code to use simple EXISTS instead of complex JOIN query will fix that.

Answer 2

I was able to solve this problem by applying reorder to the result of the pg_search result.

search_command.rb

class SearchArticlesCommand
  def initialize(params = {})
    @since = params['since_date']
    @keys = params['search_query']
    @category = params['category']
  end

  def execute
    Article.unscoped do
      query = Article.article
      query = if @since.present?
                query.since_date(@since)
              else
                query.published
              end
      query = query.for_category(@category) if @category.present?
      query = query.search_by_keywords(@keys).reorder('updated_at DESC') if @keys.present?
      query
    end
  end
end

I also overrode for_category (not required)

article.rb

  scope :for_category, (lambda do |category|
    published
      .joins(:categories)
      .group(:id)
      .where('comfy_cms_categories.label' => category)
      .select('comfy_cms_pages.*')
  end)