Previously, relation calculations such as count would make a query
even when passed a contradiction,
contradiction relation
means passing an empty array for eg:-
User.where(id: []).countIt does not make sense to call a database for such contradictory relations.
Before
So, before Rails 7 was introduced,
the database was called if the relation used for count, sum, average, minimum
and maximum would be contradictory.
=> Product.where(title: []).count
Product Count (4.7ms) SELECT COUNT(*) FROM "products" WHERE 1=0
=> 0
=> Product.where(title: []).sum(:price)
Product Sum (17.5ms) SELECT SUM("products"."price") FROM "products" WHERE 1=0
=> 0
=> Product.where(title: []).average(:price)
Product Average (3.5ms) SELECT AVG("products"."price") FROM "products" WHERE 1=0
=> nil
=> Product.where(title: []).minimum(:id)
Product Minimum (5.0ms) SELECT MIN("products"."id") FROM "products" WHERE 1=0
=> nil
=> Product.where(title: []).maximum(:id)
Product Minimum (5.0ms) SELECT MAX("products"."id") FROM "products" WHERE 1=0
=> nil As it can be seen, it would make a query to the database even when passed a contradiction.
After
Now after Rails 7, it avoids making a query to the database.
=> Product.where(title: []).count
=> 0
=> Product.where(title: []).sum(:price)
=> 0
=> Product.where(title: []).average(:price)
=> nil
=> Product.where(title: []).minimum(:id)
=> nil
=> Product.where(title: []).maximum(:id)
=> nil Check out the PR for more details.