diff --git a/README.md b/README.md
index 71ca051..02736cc 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,7 @@
 Go tryout. Single board imageboard.
 
 ## Prerequisites
-Create db.  
-Run migrations from `migrations`.  
-Create `.env` file from `.env.example`, change env vars to your needs.
\ No newline at end of file
+1. Go 1.13+.
+2. PostgreSQL.
+3. Create `.env` file from `.env.example`, change env vars to your needs.
+4. Create db with the name that is specified in `.env` file in `POSTGRES_URL` env var.
diff --git a/repositories/posts_repository.go b/repositories/posts_repository.go
index b02d4c4..2817c3c 100644
--- a/repositories/posts_repository.go
+++ b/repositories/posts_repository.go
@@ -236,8 +236,9 @@ func (r *PostsRepository) ArchiveThreadsFrom(t time.Time) error {
 	sql := `
 		UPDATE posts
 		SET is_archived = true
-		WHERE
-			is_archived != true
+		WHERE 
+			is_parent = true
+			AND is_archived != true
 			AND updated_at <= $1
 	`