fix: rewritten loader logic so it orders owners by pets (#486)

* rewritten loader logic so it orders owners by pets

* switched ids of owners so their order don't match up with pets

* moved sorting logic to sql query from code

* edited slides to reflect new logic

migrations/002.do.sql

@@ -1,2 +1,2 @@
 INSERT INTO owners (name) VALUES ('Jennifer'), ('Simon');
-INSERT INTO pets (name, owner) VALUES ('Max', 1), ('Charlie', 2);
+INSERT INTO pets (name, owner) VALUES ('Max', 2), ('Charlie', 1);

slides.md

@@ -456,6 +456,8 @@ export async function ownersByPetNames(db, petNames) {
  INNER JOIN pets
  ON pets.owner = owners.id
  AND pets.name = ANY(${petNames})
+ ORDER BY
+ ARRAY_POSITION((${petNames}), pets.name)`
  `
  )
 
@@ -676,9 +678,7 @@ onResolution called
  "errors": [
  {
  "message": "Invalid User ID",
- "locations": [
- { "line": 2, "column": 3 }
- ],
+ "locations": [{ "line": 2, "column": 3 }],
  "path": ["findUser"],
  "extensions": {
  "code": "USER_ID_INVALID",
@@ -797,7 +797,6 @@ await gateway.listen({ port: 4000 })
 
 # Step 8: Solution / 2
 
-
 ```js
 // index.js
 import Fastify from 'fastify'

src/step-04-n+1/lib/db.js

@@ -9,12 +9,13 @@ export async function loadPets(db) {
 export async function ownersByPetNames(db, petNames) {
  const { rows } = await db.query(
  SQL`
- SELECT owners.*
- FROM owners
- INNER JOIN pets
- ON pets.owner = owners.id
- AND pets.name = ANY(${petNames})
- `
+ SELECT owners.*
+ FROM owners
+ INNER JOIN pets
+ ON pets.owner = owners.id
+ AND pets.name = ANY(${petNames})
+ ORDER BY
+ ARRAY_POSITION((${petNames}), pets.name)`
  )
 
  return rows

src/step-04-n+1/test/n+1.test.js

@@ -32,13 +32,13 @@ test('should return owner of the pet', async t => {
  {
  name: 'Max',
  owner: {
- name: 'Jennifer'
+ name: 'Simon'
  }
  },
  {
  name: 'Charlie',
  owner: {
- name: 'Simon'
+ name: 'Jennifer'
  }
  }
  ]