The problem
It's a common case for Rails applications to have enum
fields on a model like:
class Review < ApplicationRecord
enum status: [:pending, :processing, :completed]
end
All's good until we need to sort records by their status in a specific order. For example, on reviews page records should be ordered by status in alphabetical order, but internally in DB status values are stored as integers.
We can't just add order(status: :asc)
. Previously we'd have to write some custom SQL for the task:
Review.order("
CASE status
WHEN 2 THEN 1
WHEN 0 THEN 2
WHEN 1 THEN 3
END
ASC
")
The solution
Ruby on Rails 7.0 provides a new query method #in_order_of
which accepts as arguments a column name and an array of values in order we want the records to be ordered by:
Review.in_order_of(
:status, [:complete, :pending, :processing]
)
Which translates to SQL query like:
SELECT "reviews".* FROM "reviews"
WHERE "reviews"."status" IN (2, 0, 1)
ORDER BY CASE "reviews"."status"
WHEN 2 THEN 1
WHEN 0 THEN 2
WHEN 1 THEN 3
END ASC
This works well, as long as we don't have/care about reviews with NULL
as their status.
If we try to pass nil
to the values array:
Review.in_order_of(
:status, [nil, :complete, :pending, :processing]
)
Following SQL would be created:
SELECT "reviews".* FROM "reviews"
WHERE "reviews"."status" IN (NULL, 2, 0, 1)
ORDER BY CASE "reviews"."status"
WHEN NULL THEN 1
WHEN 2 THEN 2
WHEN 0 THEN 3
WHEN 1 THEN 4
END ASC
But since NULL
in SQL is a special value and NULL != NULL
, then this query simply won't return records with NULL
as a status at all.
The improvement
Ruby on Rails 7.0.7 further improves the method: now it correctly handles the NULL
values, so the resulting query would be:
SELECT "reviews".* FROM "reviews"
WHERE (
"reviews"."status" IN (2, 0, 1)
OR "reviews"."status" IS NULL
)
ORDER BY CASE
WHEN "reviews"."status" IS NULL THEN 1
WHEN "reviews"."status" = 2 THEN 2
WHEN "reviews"."status" = 0 THEN 3
WHEN "reviews"."status" = 1 THEN 4
END ASC
Now it does exactly what we need without writing any custom SQL queries.
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