Rails gem Ransack -> search 'or condition' with 'is null' and a specific value (field=x OR field IS NULL)

问题:

I made a support ticket system for our supporters - programmed with ruby on rails (Ruby 1.9.3 Rails 3.2)

There is a ticket model with a belongs_to association to users (supporter).

I use Ernie's gem Ransack for searching. When the supporter searches his own tickets (handled by tickets_controller.index) he should also see the unassociated tickets in the search result (views/tickets/index) (in combination with the other serach conditions eg. "date" or something else)

(So that he can take an open ticket)

expected SQL statement:

SELECT * FROM tickets WHERE ... AND (user_id=5 OR user_id IS NULL) AND ...  

I tried user_id_null_or_user_id_eq in the search form of the index-view - but that does not work (no method error)

How can I make a custom predicate (or ransacker) to solve this problem? (Thanks @Magnuss for this comment)

Unfortunately, I have no experience with Arel

Something like:

ransacker :user_null_or_eq do     ... end 

in the tickets model.

I hope this explains the problem in more detail.

Thanks for any help.

回答1:

I also had to figure this out and @TomG answer helped a lot! You really don't need to create a ransacker for this issue, it an be fixed by using the build_grouping method of ransack (that is not documented anywhere...) and put in the condition you need with 'or' condition.

I used it to search items to add to a cage but wanted to show the user only items that are not already in my cage (and also not assigned to any other cage), so in my controller:

   @search = Cage.ransack(params[:q])    @search.build_grouping({:m => 'or', :storage_id_not_eq => @cage_item.id, :storage_id_null => true})      @results_count = @search.result(:distinct => true).length    @items = @search.result(:distinct => true).paginate(:per_page => 20, :page => params[:page] || 1)     @search.build_condition if @search.conditions.empty?    @search.build_sort if @search.sorts.empty? 

So when I'm printing the query ransack is running it will show:

 @search.result.to_sql "SELECT `specimens`.* FROM `specimens`  WHERE (`specimens`.`deleted_at` IS NULL) AND ((`specimens`.`storage_id` != 183 OR `specimens`.`storage_id` IS NULL))" 

and if I add a name query:

@search.result.to_sql "SELECT `specimens`.* FROM `specimens`  WHERE (`specimens`.`deleted_at` IS NULL) AND ((`specimens`.`name` LIKE '%root%' AND (`specimens`.`storage_id` != 183 OR `specimens`.`storage_id` IS NULL)))" 

Hope this helps you or someone else with having trouble using OR in ransack conditions instead of the basic AND.

回答2:

OK - here is my own solution - inspired by graywh (thank you very much): ransack/issues/290

You can add a new grouping node -with an 'or'-combinator- to the ransack object.

In index view I changed f.select :user_id_eq to select_tag ...

tickets_controller.index:

@q = Ticket.search(params[:q])   if params[:user_id_eq] && params[:user_id_eq]!=''     @q.build_grouping({:m => 'or', :user_id_eq => params[:user_id_eq], :user_id_null => true})   end 

回答3:

You could build your query params like this

q: {g: [ {m: 'or', user_id_eq: 5, user_id_null: 1} ] } 

where this:

user_id_null: 1 

is only flag to search for null value

文章来源: Rails gem Ransack -> search 'or condition' with 'is null' and a specific value (field=x OR field IS NULL)