Ruby on Rails query yielding unexpected results - ruby-on-rails

Question

This is a followup to an earlier thread: Ruby on Rails query not working properly.
As noted, I have several listings. In particular, a listing has_many :spaces, through: :designations and has_many :amenities, through: :offerings.
I define filters to restrict the listings that get shown.
The two main ones are:
# filter by amenities
if params[:search][:amenity_ids].present? && params[:search][:amenity_ids].reject(&:blank?).size > 0
#listings = #listings.joins(:amenities).where(amenities: { id: params[:search][:amenity_ids].reject(&:blank?) }).group('listings.id').having('count(*) >= ?', params[:search][:amenity_ids].reject(&:blank?).size)
end
# filter by space type
if params[:search][:space_ids].present? && params[:search][:space_ids].reject(&:blank?).size > 0
#listings = #listings.joins(:spaces).where('space_id IN (?)', params[:search][:space_ids].reject(&:blank?)).uniq
end
(Note that these reflect the solution indicated in the earlier thread.)
The first filter says: get all of the listings that have ALL of the selected amenities.
The second filter says: get all of the listings that match ANY of the selected space types.
But one issue remains. If I filter for space types 1 and 2 and amenities 1 and 2, I get listing A (which has space types 1 and 2 and amenity 2).
But I should presumably get [] since no listing has both amenities 1 and 2.
What is going on with these queries? Should they not be independent, but chainable?
Here is the output (I disabled the other filters for clarity):
Started GET "/listings/search?utf8=%E2%9C%93&search%5Baddress%5D=London%2C+United+Kingdom&search%5Bprice_min%5D=0&search%5Bprice_max%5D=1000.0&search%5Bprice_lower%5D=0&search%5Bprice_upper%5D=1000&search%5Bsize_min%5D=0&search%5Bsize_max%5D=1000&search%5Bsize_lower%5D=0&search%5Bsize_upper%5D=1000&search%5Bspace_ids%5D%5B%5D=1&search%5Bspace_ids%5D%5B%5D=2&search%5Bspace_ids%5D%5B%5D=&search%5Bamenity_ids%5D%5B%5D=1&search%5Bamenity_ids%5D%5B%5D=2&search%5Bamenity_ids%5D%5B%5D=&search%5Bsort_by%5D=Distance&commit=Apply+Filters" for ::1 at 2015-10-31 14:25:58 +0000
ActiveRecord::SchemaMigration Load (0.4ms) SELECT "schema_migrations".* FROM "schema_migrations"
Processing by ListingsController#search as HTML
Parameters: {"utf8"=>"✓", "search"=>{"address"=>"London, United Kingdom", "price_min"=>"0", "price_max"=>"1000.0", "price_lower"=>"0", "price_upper"=>"1000", "size_min"=>"0", "size_max"=>"1000", "size_lower"=>"0", "size_upper"=>"1000", "space_ids"=>["1", "2", ""], "amenity_ids"=>["1", "2", ""], "sort_by"=>"Distance"}, "commit"=>"Apply Filters"}
(1.5ms) SELECT MAX("listings"."price") FROM "listings"
(0.6ms) SELECT MAX("listings"."size") FROM "listings"
Listing Load (4.4ms) SELECT DISTINCT "listings".* FROM "listings" INNER JOIN "offerings" ON "offerings"."listing_id" = "listings"."id" INNER JOIN "amenities" ON "amenities"."id" = "offerings"."amenity_id" INNER JOIN "designations" ON "designations"."listing_id" = "listings"."id" INNER JOIN "spaces" ON "spaces"."id" = "designations"."space_id" WHERE "amenities"."id" IN (1, 2) AND (space_id IN ('1','2')) GROUP BY listings.id HAVING count(*) >= 2 LIMIT 24 OFFSET 0
Image Load (0.5ms) SELECT "images".* FROM "images" WHERE "images"."listing_id" = $1 ORDER BY "images"."id" ASC LIMIT 1 [["listing_id", 1]]
Space Load (0.6ms) SELECT "spaces".* FROM "spaces" INNER JOIN "designations" ON "spaces"."id" = "designations"."space_id" WHERE "designations"."listing_id" = $1 [["listing_id", 1]]
Rendered listings/_map_infowindow.html.erb (56.1ms)
Rendered listings/_price_slider.html.erb (0.7ms)
Rendered listings/_size_slider.html.erb (0.6ms)
Space Load (0.4ms) SELECT "spaces".* FROM "spaces"
Amenity Load (0.4ms) SELECT "amenities".* FROM "amenities"
Rendered scripts/_checkbox_toggle.html.erb (0.5ms)
Rendered listings/_search_filters.html.erb (75.5ms)
(0.4ms) SELECT "spaces"."name" FROM "spaces" INNER JOIN "designations" ON "spaces"."id" = "designations"."space_id" WHERE "designations"."listing_id" = $1 [["listing_id", 1]]
CACHE (0.0ms) SELECT "images".* FROM "images" WHERE "images"."listing_id" = $1 ORDER BY "images"."id" ASC LIMIT 1 [["listing_id", 1]]
User Load (0.7ms) SELECT "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1 [["id", 3]]
Avatar Load (0.7ms) SELECT "avatars".* FROM "avatars" WHERE "avatars"."user_id" = $1 ORDER BY "avatars"."id" ASC LIMIT 1 [["user_id", 3]]
Rendered listings/_listing_grid.html.erb (80.8ms)
(3.1ms) SELECT DISTINCT COUNT(DISTINCT "listings"."id") AS count_id, listings.id AS listings_id FROM "listings" INNER JOIN "offerings" ON "offerings"."listing_id" = "listings"."id" INNER JOIN "amenities" ON "amenities"."id" = "offerings"."amenity_id" INNER JOIN "designations" ON "designations"."listing_id" = "listings"."id" INNER JOIN "spaces" ON "spaces"."id" = "designations"."space_id" WHERE "amenities"."id" IN (1, 2) AND (space_id IN ('1','2')) GROUP BY listings.id HAVING count(*) >= 2
Rendered scripts/_map.html.erb (2.9ms)
Rendered scripts/_shuffle.html.erb (0.3ms)
Rendered listings/search.html.erb within layouts/application (178.7ms)
Rendered layouts/_head.html.erb (475.7ms)
Rendered scripts/_address_autocomplete.html.erb (0.3ms)
Rendered listings/_search_address.html.erb (13.7ms)
User Load (0.4ms) SELECT "users".* FROM "users" WHERE "users"."id" = $1 ORDER BY "users"."id" ASC LIMIT 1 [["id", 3]]
(0.5ms) SELECT DISTINCT "conversations"."id" FROM "conversations" WHERE (sender_id = 3 OR recipient_id = 3)
(0.5ms) SELECT DISTINCT "messages"."conversation_id" FROM "messages" WHERE ("messages"."user_id" != $1) AND "messages"."read" = $2 [["user_id", 3], ["read", "false"]]
CACHE (0.0ms) SELECT "avatars".* FROM "avatars" WHERE "avatars"."user_id" = $1 ORDER BY "avatars"."id" ASC LIMIT 1 [["user_id", 3]]
Rendered layouts/_navbar.html.erb (32.5ms)
Rendered scripts/_fade_error.html.erb (0.4ms)
Rendered scripts/_transparent_navbar.html.erb (0.3ms)
Completed 200 OK in 1045ms (Views: 688.6ms | ActiveRecord: 30.6ms)
I have also tried adding raise 'test' in order to do some testing in the better_errors live shell. I discovered:
>> #listings
=> #<ActiveRecord::Relation []>
>> #listings = #listings.joins(:spaces).where('space_id IN (?)', params[:search][:space_ids].reject(&:blank?)).uniq
=> #<ActiveRecord::Relation [#<Listing id: 1, title: "Test 1", address: "New Inn Passage, London WC2A 2AE, UK", latitude: 51.5139664, longitude: -0.1167323, size: 1000, min_lease: 1, price: #<BigDecimal:7f89ec245c98,'0.1E4',9(18)>, description: "Test 1", user_id: 3, state: "public", created_at: "2015-10-30 17:37:04", updated_at: "2015-10-30 17:37:04">]>
>>
Why is this happening and how can I fix it?
Any help would be greatly appreciated.

Answer 1

The issue is with how you are determining that all of the amenities have been matched.
When you are only joining the amenities then the count of the rows (prior to grouping) for a listing is the number of matched amenities, so the having clause does what you want.
When you join the spaces table too, then the number of rows (again prior to grouping) for a listing is the number of matches amenities times the number of matched rows. In your example there are 2 spaces and 1 amenity, so the count is 2 and your having clause is satisfied.
If instead of filtering on count(*) you filtered on count(distinct amenities.id) then you should be counting the number of amenity rows that were joined, which should produce the desired result.

Answer 2

I may have figured out the issue. I did the following in the console to test:
Set #listings = Listing.all.
Set #listings = #listings.joins(:amenities).where(amenities: { id: ['1', '2'].reject(&:blank?) }).group('listings.id').having('count(*) >= ?', ['1', '2'].reject(&:blank?).size).
This produces: => #<ActiveRecord::Relation []>, as desired.
I then checked to see what would happen if I were to do: #listings.joins(:spaces).
This produces: => #<ActiveRecord::Relation [#<Listing id: 1, title: "Test 1", address: "New Inn Passage, London WC2A 2AE, UK", latitude: 51.5139664, longitude: -0.1167323, size: 1000, min_lease: 1, price: #<BigDecimal:7ffcb02ce890,'0.1E4',9(18)>, description: "Test 1", user_id: 3, state: "public", created_at: "2015-10-30 17:37:04", updated_at: "2015-10-30 17:37:04">]>, even though #listings was initially [].
So the problem has to do with the joins(:spaces) in the second filter.
In order to make sure that #listings remains [] in the event that that is the result of the first filter, I added the extra condition && #listings.present? to the second filter, yielding:
if params[:search][:space_ids].present? && params[:search][:space_ids].reject(&:blank?).size > 0 && #listings.present?
That extra condition prevents the second filter from being executed and returning results that should not be returned.
This feels like an ugly hack, and I would welcome better solutions, but it seems to work.