[next] MongoDB Indexes (#2142)

* feat: added mongo indexing support

* fix: fixed typescript issue

* chore: better types

* fix: revert debug stuff

* fix: addressed ts error

* feat: added config option to disable auto-indexing

* chore: reordered imports

* refactor: cleaned up some filepaths

src/core/server/models/comment.ts

@@ -19,8 +19,11 @@ import {
   nodesToEdges,
   NodeToCursorTransformer,
   OrderedConnectionInput,
-} from "talk-server/models/connection";
-import Query from "talk-server/models/query";
+} from "talk-server/models/helpers/connection";
+import Query, {
+  createConnectionOrderVariants,
+  createIndexFactory,
+} from "talk-server/models/helpers/query";
 import { TenantResource } from "talk-server/models/tenant";
 
 function collection(mongo: Db) {
@@ -137,6 +140,54 @@ export interface Comment extends TenantResource {
   metadata?: Record<string, any>;
 }
 
+export async function createCommentIndexes(mongo: Db) {
+  const createIndex = createIndexFactory(collection(mongo));
+
+  // UNIQUE { id }
+  await createIndex({ tenantID: 1, id: 1 }, { unique: true });
+
+  const variants = createConnectionOrderVariants<Readonly<Comment>>([
+    { createdAt: -1 },
+    { createdAt: 1 },
+    { replyCount: -1, createdAt: -1 },
+    { "actionCounts.REACTION": -1, createdAt: -1 },
+  ]);
+
+  // Story based Comment Connection pagination.
+  // { storyID, ...connectionParams }
+  await variants(createIndex, {
+    tenantID: 1,
+    storyID: 1,
+    status: 1,
+  });
+
+  // Story based Comment Connection pagination that are flagged.
+  // { storyID, ...connectionParams }
+  await variants(createIndex, {
+    tenantID: 1,
+    storyID: 1,
+    status: 1,
+    "actionCounts.FLAG": 1,
+  });
+
+  // Story + Reply based Comment Connection pagination.
+  // { storyID, ...connectionParams }
+  await variants(createIndex, {
+    tenantID: 1,
+    storyID: 1,
+    parentID: 1,
+    status: 1,
+  });
+
+  // Author based Comment Connection pagination.
+  // { authorID, ...connectionParams }
+  await variants(createIndex, {
+    tenantID: 1,
+    authorID: 1,
+    status: 1,
+  });
+}
+
 export type CreateCommentInput = Omit<
   Comment,
   | "id"
@@ -670,6 +721,7 @@ function applyInputToQuery(
   input: CommentConnectionInput,
   query: Query<Comment>
 ) {
+  // NOTE: (wyattjoh) if we ever extend these, ensure that the new order variant is added as an index into the `createCommentConnectionOrderVariants` function.
   switch (input.orderBy) {
     case GQLCOMMENT_SORT.CREATED_AT_DESC:
       query.orderBy({ createdAt: -1 });