Add comments user pagination index

api/v1_users_comments.go

@@ -8,13 +8,12 @@ import (
 func (app *ApiServer) v1UsersComments(c *fiber.Ctx) error {
 
 	sql := `
-	SELECT comment_id as id
-	FROM comments
-	LEFT JOIN comment_threads USING (comment_id)
-	WHERE user_id = @user_id
-	AND entity_type = 'Track'
-	AND comments.is_delete = false
-	`
+		SELECT comment_id as id
+		FROM comments
+		WHERE user_id = @user_id
+		AND entity_type = 'Track'
+		AND comments.is_delete = false
+		`
 
 	args := pgx.NamedArgs{
 		"user_id": app.getUserId(c),

ddl/migrations/0224_comments_user_track_created_at_idx.sql

@@ -0,0 +1,14 @@
+-- Supports /v1/users/:id/comments pagination:
+--
+--   WHERE user_id = ?
+--     AND entity_type = 'Track'
+--     AND is_delete = false
+--   ORDER BY created_at DESC
+--
+-- Without this index, the endpoint scans and sorts the full comments table for
+-- every user-comments page request.
+CREATE INDEX CONCURRENTLY IF NOT EXISTS comments_user_track_created_at_idx
+    ON public.comments USING btree (user_id, created_at DESC)
+    INCLUDE (comment_id)
+    WHERE entity_type = 'Track'
+      AND is_delete = false;