feat(postgres): add delete to collection key

src/postgres/inventory/collection/PGCollectionKey.ts

@@ -212,6 +212,42 @@ class PGCollectionKey implements CollectionKey<PGObjectType.Value> {
         return objectToMap(result.rows[0]['object'])
       }
   )
+
+  /**
+   * Deletes a value in our Postgres database using a given key. If no value
+   * could be deleted, an error will be thrown.
+   *
+   * This method, unlike many others in Postgres collections, is not batched.
+   */
+  public delete = (
+    !this._pgClass.isDeletable
+      ? null
+      : async (context: mixed, key: PGObjectType.Value): Promise<PGObjectType.Value> => {
+        // First things first, we need to get our Postgres client from the
+        // context. This means first verifying our client exists on the
+        // context.
+        if (!isPGContext(context)) throw isPGContext.error()
+        const { client } = context
+
+        // This is a pretty simple query. Delete the row that matches our key
+        // and return the deleted row.
+        const query = sql.compile(sql.query`
+          with deleted as (
+            delete from ${sql.identifier(this._pgNamespace.name, this._pgClass.name)}
+            where ${this._getSQLKeyCondition(key)}
+            returning *
+          )
+          select row_to_json(x) as object from deleted as x
+        `)()
+
+        const result = await client.query(query)
+
+        if (result.rowCount < 1)
+          throw new Error(`No values were deleted in collection '${this._collection.name}' using key '${this.name}'.`)
+
+        return objectToMap(result.rows[0]['object'])
+      }
+  )
 }
 
 export default PGCollectionKey

src/postgres/inventory/collection/__tests__/PGCollectionKey-test.js

@@ -165,3 +165,44 @@ test('update fails when trying to update a value that does not exist', async ()
     expect(error.message).toBe('No values were updated in collection \'people\' using key \'email\'.')
   }
 })
+
+test('delete will delete things from the database', async () => {
+  await client.query(`
+    insert into c.person (id, name, email, about) values
+      (1, 'John Smith', '[email protected]', null),
+      (2, 'Sara Smith', '[email protected]', null),
+      (3, 'Budd Deey', '[email protected]', 'Just a friendly human');
+  `)
+
+  await client.query(`
+    insert into c.compound_key (person_id_1, person_id_2) values
+      (1, 2),
+      (2, 1),
+      (3, 2),
+      (3, 1);
+  `)
+
+  const selectQuery = `
+    select row_to_json(x) as object from c.compound_key as x
+    union all
+    select row_to_json(x) as object from c.person as x
+  `
+
+  const { rows: initialRows } = await client.query(selectQuery)
+
+  const values = await Promise.all([
+    collectionKey1.delete({ client }, new Map([['person_id_1', 1], ['person_id_2', 2]])),
+    collectionKey1.delete({ client }, new Map([['person_id_1', 2], ['person_id_2', 1]])),
+    collectionKey1.delete({ client }, new Map([['person_id_1', 3], ['person_id_2', 1]])),
+    collectionKey2.delete({ client }, new Map([['email', '[email protected]']])),
+  ])
+
+  expect(values.map(mapToObject)).toEqual([
+    { 'person_id_1': 1, 'person_id_2': 2 },
+    { 'person_id_1': 2, 'person_id_2': 1 },
+    { 'person_id_1': 3, 'person_id_2': 1 },
+    { 'id': 1, 'name': 'John Smith', 'email': '[email protected]', 'about': null, 'created_at': values[3].get('created_at') },
+  ])
+
+  expect((await client.query(selectQuery)).rows).toEqual([initialRows[2], initialRows[5], initialRows[6]])
+})