.apply_scopes MUST be called before .where

[enwood]

Ignacio Responds:
Nice find! The implementation of apply_scopes is unfortunately old and
fragile. We really need to replace it with something stronger based on
the latest ActiveRecord/Arel syntax.

Tim's Submission:
It seems that it is very important to call .apply_scopes BEFORE calling a .where clause, especially if the scope is effectively empty.

Calling .apply_scopes with an empty scope AFTER a .where clause causes the .where clause to be ignored!

An example:

In an #index function, I watch for search and sorting scopes:

  def index
    scopes = {                                                               
      :search => [params[:search], :user_name, :search_text], 
      :order_by => parse_sort_param(:id, :date_searched, :user_name, :matches, :search_text)
    }
    @searches = Search
         .where('date_searched >= ? AND date_searched <= ?', params[:start_date], params[:end_date] )
         .apply_scopes(scopes).order('date_searched DESC')
         .paginate(:per_page => 200, :page => params[:page])

I've found, though, that if my request does not include a search and an order_by parameter, the call to apply_scopes causes the .where clause to be ignored!

For example, this is the request to filter by date:

GET "/admin/searches?start_date=04%2F01%2F2015&end_date=04%2F30%2F2015"

And this is the SQL that's generated:

[INFO ] Parameters: {"start_date"=>"04/01/2015", "end_date"=>"04/30/2015"} [DEBUG] Search Load (98.4ms) EXEC sp_executesql N'SELECT TOP (200) [__rnt].* FROM ( SELECT ROW_NUMBER() OVER (ORDER BY date_searched DESC) AS [__rn], [searches].* FROM [searches] ) AS [__rnt] WHERE [__rnt].[__rn] > (0) ORDER BY [__rnt].[__rn] ASC'

How bizarre!

But, if it does include a search parameter to be used by apply_scopes:

[INFO ] GET "/admin/searches?start_date=04%2F01%2F2015&end_date=04%2F30%2F2015&search=Tim"

I get this SQL:

[DEBUG] Search Load (8.8ms) EXEC sp_executesql N'SELECT TOP (200) [__rnt].* FROM ( SELECT ROW_NUMBER() OVER (ORDER BY date_searched DESC) AS [__rn], [searches].* FROM [searches] WHERE (date_searched >= N''04/01/2015'' AND date_searched <= N''04/30/2015'') AND (((searches.user_name LIKE N''%Tim%'') OR (searches.search_text LIKE N''%Tim%''))) ) AS [__rnt] WHERE [__rnt].[__rn] > (0) ORDER BY [__rnt].[__rn] ASC'

SOLUTION:

If I reverse the order of the .where and the .apply_scopes, it works as expected, which is completely unintuitive!

@searches = Search
  .apply_scopes(scopes)
  .order('date_searched DESC')
  .where('date_searched >= ? AND date_searched <= ?', params[:start_date], params[:end_date] )

[DEBUG]   Search Load (6.5ms)  EXEC sp_executesql N'SELECT TOP (200) [__rnt].* FROM ( SELECT ROW_NUMBER() OVER (ORDER BY date_searched DESC) AS [__rn], [searches].* FROM [searches] WHERE (date_searched >= N''04/01/2015'' AND date_searched <= N''04/30/2015'') ) AS [__rnt] WHERE [__rnt].[__rn] > (0) ORDER BY [__rnt].[__rn] ASC'

In thinking about crafting this query, it made more sense to me to reduce the overall set first (with the .where clause), and then apply any search (or sorting) within that.

[iox]

Thanks for the great bug report!