This is critical to debug bugs related to subscriptions.
Essentially, `has_and_belongs_to_many` doesn't give us the option for
any other column that the foreign keys themselves:
> A has_and_belongs_to_many association creates a direct many-to-many
> connection with another model, with no intervening model.
Source: https://guides.rubyonrails.org/v3.2/association_basics.html#the-has_and_belongs_to_many-association
Note however, that there's no way to update an order_cycle_schedule,
that I can think of but `updated_at` doesn't do any harm.
It's much clearer to read this way:
```
== OldMigrationsRemoved: migrating ===========================================
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:
You haven't updated your dev environment in a long time!
Legacy migration files before 2019 have now been removed.
Run `rails db:schema:load` before running `rails db:migrate`.
```
A migration's `up` method is only run when the migration needs to be
applied. The only case we could have a higher version number is when a
migration with a higher version got merged before the current one. And
in that case, we still want this migration to fail, because it hasn't
been applied yet.
Activate paper_trail in order_cycles and schedules and track each others ids
An alternative way of doing this would be to use a gem for paper_trail associations but this way we avoid adding a new dependency to the app
It looks like this was probably changed whilst resolving a merge conflict somewhere. The number doesn't match the last migration file, and it's breaking the ofn-install CI build (as well as migrations on fresh servers).
The following query
```sql
SELECT spree_orders . *
FROM spree_orders
WHERE spree_orders . user_id = ?
AND spree_orders . completed_at IS ?
AND spree_orders . created_by_id = ?
ORDER BY created_at DESC LIMIT ?
```
performs quite badly even though LIMIT is always 1 because:
* ORDER BY requires sorting by a column which is not indexed therefore
a sequential scan is performed.
* Although `completed_at` is indexed, `user_id` and `created_by_id` are
not causing a sequential scan.
To make it worse this query is executed very often in the following
controllers among others also related to checkout:
* CartController#populate
* EnterprisesController#Shop
* LineItemsController#bought
* ShopController#products
* ShopController#order_cycle
In some cases this query alone accounts for 66.8% of the total time
of the endpoint.
Results
See by yourself. We move from 56.643ms to 0.077ms. Pretty neat.
```
openfoodnetwork=> explain analyze SELECT "spree_orders".* FROM "spree_orders" WHERE "spree_orders"."user_id" = 1 AND "spree_orders"."completed_at" IS NULL AND "spree_orders"."created_by_id" = 1 ORDER BY created_at DESC LIMIT 1;
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------
Limit (cost=11753.03..11753.04 rows=1 width=195) (actual time=56.580..56.580 rows=0 loops=1)
-> Sort (cost=11753.03..11753.04 rows=1 width=195) (actual time=56.578..56.578 rows=0 loops=1)
Sort Key: created_at DESC
Sort Method: quicksort Memory: 25kB
-> Seq Scan on spree_orders (cost=0.00..11753.02 rows=1 width=195) (actual time=56.571..56.571 rows=0 loops=1)
Filter: ((completed_at IS NULL) AND (user_id = 1) AND (created_by_id = 1))
Rows Removed by Filter: 256135
Planning time: 0.252 ms
Execution time: 56.643 ms
(9 rows)
openfoodnetwork=> CREATE INDEX ON spree_orders (completed_at, user_id, created_by_id, created_at);
CREATE INDEX
openfoodnetwork=> explain analyze SELECT "spree_orders".* FROM "spree_orders" WHERE "spree_orders"."user_id" = 1 AND "spree_orders"."completed_at" IS NULL AND "spree_orders"."created_by_id" = 1 ORDER BY created_at DESC LIMIT 1;
mit (cost=8.45..8.46 rows=1 width=195) (actual time=0.030..0.030 rows=0 loops=1)
-> Sort (cost=8.45..8.46 rows=1 width=195) (actual time=0.029..0.029 rows=0 loops=1)
Sort Key: created_at DESC
Sort Method: quicksort Memory: 25kB
-> Index Scan using spree_orders_completed_at_user_id_created_by_id_created_at_idx on spree_orders (cost=0.42..8.44 rows=1 width=195) (actual time=0.021..0.021 rows=0 loops=1)
Index Cond: ((completed_at IS NULL) AND (user_id = 1) AND (created_by_id = 1))
Planning time: 0.199 ms
Execution time: 0.077 ms
```
