This removes an N+1 with taggings but doesn't solve the one with tags.
Using `includes(taggings: :base_tags)` based on
47da5036de/lib/acts_as_taggable_on/taggable.rb (L83-L84)
wasn't enough to solve it and I got to stop here. This is scope-creeping
too much.
We get from an initial INNER JOIN with variants and products to fetch
the variant overrides + N queries like:
```sql
SELECT "spree_variants".* FROM "spree_variants" WHERE
"spree_variants"."deleted_at" IS NULL AND "spree_variants"."id" = $1
LIMIT 1 [["id", 1545]]
SELECT "spree_products".* FROM "spree_products" WHERE
"spree_products"."id" = $1 LIMIT 1 [["id", 604]]
```
to the same initial INNER JOIN + just 2 queries like:
```sql
SELECT "spree_variants".* FROM "spree_variants" WHERE
"spree_variants"."deleted_at" IS NULL AND "spree_variants"."id" IN
(1551, 1554)
SELECT "spree_products".* FROM "spree_products" WHERE
"spree_products"."deleted_at" IS NULL AND "spree_products"."id" IN (606,
607)
```
In the line below we filter them out in Ruby so it's a waste of
resources. The fundamental difference is that `#includes` and
`#references` results in LEFT JOINs, whereas `#joins` results in INNER
JOIN, and because there's a default scope on `deleted_at IS NULL`, these
are not included in the result set.
This however, requires us to move away from the current algorithm but
unfortunately we can't refactor it completely yet.
Before:
```sql
SELECT *
FROM "variant_overrides"
LEFT OUTER
JOIN "spree_variants"
ON "spree_variants"."id" = "variant_overrides"."variant_id"
AND "spree_variants"."deleted_at" IS NULL
LEFT OUTER
JOIN "spree_products"
ON "spree_products"."id" = "spree_variants"."product_id"
AND "spree_products"."deleted_at" IS NULL
WHERE "variant_overrides"."permission_revoked_at" IS NULL
AND "variant_overrides"."hub_id" IN (
SELECT "enterprises"."id"
FROM "enterprises"
INNER
JOIN "enterprise_roles"
ON "enterprise_roles"."enterprise_id" = "enterprises"."id"
WHERE (enterprise_roles.user_id = ?)
AND (sells != 'none')
ORDER BY name)
```
After:
```sql
SELECT "variant_overrides".*
FROM "variant_overrides"
INNER
JOIN "spree_variants"
ON "spree_variants"."id" = "variant_overrides"."variant_id"
AND "spree_variants"."deleted_at" IS NULL
INNER
JOIN "spree_products"
ON "spree_products"."id" = "spree_variants"."product_id"
AND "spree_products"."deleted_at" IS NULL
WHERE "variant_overrides"."permission_revoked_at" IS NULL
AND "variant_overrides"."hub_id" IN (
SELECT "enterprises"."id"
FROM "enterprises"
INNER
JOIN "enterprise_roles"
ON "enterprise_roles"."enterprise_id" = "enterprises"."id"
WHERE (enterprise_roles.user_id = ?)
AND (sells != 'none')
ORDER BY name)
```
This is covered in the test suite by
spec/controllers/admin/variant_overrides_controller_spec.rb:72. It keeps
passing so we're good to go.
DEPRECATION WARNING: It looks like you are eager loading table(s) (one of: variant_overrides, enterprises, enterprise_roles) that are referenced in a string SQL snippet. For example:
Post.includes(:comments).where("comments.title = 'foo'")
Currently, Active Record recognizes the table in the string, and knows to JOIN the comments table to the query, rather than loading comments in a separate query. However, doing this without writing a full-blown SQL parser is inherently flawed. Since we don't want to write an SQL parser, we are removing this functionality. From now on, you must explicitly tell Active Record when you are referencing a table from a string:
Post.includes(:comments).where("comments.title = 'foo'").references(:comments)
If you don't rely on implicit join references you can disable the feature entirely by setting `config.active_record.disable_implicit_join_references = true`. (called from collection at /home/user/Github/openfoodnetwork/app/controllers/admin/variant_overrides_controller.rb:77)
