Basically, I have a Listing model, where each listing has a country id. I need the country name in my search results view. I know I can do @listing.country.name, but this performs an extra query for each listing in my search results. I'm using Thinking Sphinx, and in my controller I have
@listings = Listing.search(@ts_params).page(page_num).per(limit)
I have tried adding .includes(:countries) and variations thereof but no luck.
What's the best way to go about this? I want the country data to be fetched in the same query as the listings.
I have exactly the same issue with listing images - it is performing an extra query for every listing to find the image, when surely it can be done in one with joins.
Are you trying to eager load the associated model (to avoid an N + 1 query problem), or are you trying to load the associated model into fields on the parent model?
If it's the former, you're probably better off forgetting about :select and instead of :joins using:
ts_params[:sql][:include] = :countries, :listing_images
Now you should be able to call listing.countries and listing.listing_images to access child models, as normal.
Thinking Sphinx provides functionality to eager load associated entities, so for eager loading we don't need to add [:sql]. Following is the way to do this.
For eager loading associated entities using sphinx.
ts_params[:include] = [:country, :listing_image]
I managed to solve this using the :sql hash provided by Thinking Sphinx. I now have the following:
@ts_params[:sql][:joins] = "INNER JOIN countries ON countries.id = listings.country_id INNER JOIN listing_images ON listing_images.listing_id = listings.id"
@ts_params[:sql][:select] = "listings.*, countries.name as country_name, listing_images.image as image_name"
This is correctly retrieving the country name and image name, but I still have a bit of work to do in making it work with the images - I think that will deserve its own question!
Current v4 syntax is:
Article.search :sql => {:include => :user}
Ref: https://freelancing-gods.com/thinking-sphinx/v4/searching.html
来源：https://stackoverflow.com/questions/18946007/loading-data-from-associated-model-in-same-query-in-rails