Sure thing,
*DB setup*
require 'sequel'
DB = Sequel.postgres(database: 'sequel_test', host: 'localhost', user:
'postgres')
*Migration*
Sequel.migration do
change do
create_table(:orders) do
primary_key :id
end
create_table(:payments) do
primary_key :id
foreign_key :order_id, :orders, null: false, index: { unique: true }
end
end
end
*Example*
require './db'
class Payment < Sequel::Model
end
class Order < Sequel::Model
one_to_one :payment
end
#####
# Example 1: Assigning an already existing one_to_one relation using the
setter causes (incorrect in my opinion) not null error on FK
#####
o = Order.create
o.payment = Payment.new
# Following line fails with ERROR: null value in column "order_id" of
relation "payments" violates not-null constraint (PG::NotNullViolation)
DETAIL: Failing row contains (1, null).
o.payment = Payment.new
# The above generates the following logs in Postgres:
# Feb 11 13:32:24 hp postgres[156074]: 2021-02-11 13:32:24.769 CST [156074]
ERROR: null value in column "order_id" of relation "payments" violates
not-null constraint
# Feb 11 13:32:24 hp postgres[156074]: 2021-02-11 13:32:24.769 CST [156074]
DETAIL: Failing row contains (7, null).
# Feb 11 13:32:24 hp postgres[156074]: 2021-02-11 13:32:24.769 CST [156074]
STATEMENT: UPDATE "payments" SET "order_id" = NULL WHERE ("order_id" = 6)
#####
# Example 2: Assigning an already existing one_to_one relation without
using the setter results in correct unique constraint error on FK
#####
o = Order.create
Payment.create(order_id: o.id)
# Fails with ERROR: duplicate key value violates unique constraint
"payments_order_id_index" (Sequel::UniqueConstraintViolation) DETAIL: Key
(order_id)=(2) already exists.
Payment.create(order_id: o.id)
# The above generates the following logs in Postgres:
# Feb 11 13:32:41 hp postgres[156216]: 2021-02-11 13:32:41.234 CST [156216]
ERROR: duplicate key value violates unique constraint
"payments_order_id_index"
# Feb 11 13:32:41 hp postgres[156216]: 2021-02-11 13:32:41.234 CST [156216]
DETAIL: Key (order_id)=(7) already exists.
# Feb 11 13:32:41 hp postgres[156216]: 2021-02-11 13:32:41.234 CST [156216]
STATEMENT: INSERT INTO "payments" ("order_id") VALUES (7) RETURNING *
On Thursday, 11 February 2021 at 14:36:29 UTC+8 Jeremy Evans wrote:
> On Wed, Feb 10, 2021 at 9:37 PM Dawid Janczak <[email protected]> wrote:
>
>> Huh I just checked and oddly doing `order = Payment.new` twice issues
>> `UPDATE`, not `INSERT`. I created a small script with some comments here:
>> https://github.com/DawidJanczak/sequel-test-one-to-one/blob/main/sequel_one_to_one.rb
>>
>> There is also a migration inside `migrations` directory.
>>
>> Please let me know if you need anything else, thanks!
>>
>
> Please post your minimal self-contained example inline as a response.
>
> Thanks,
> Jeremy
>
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