Delete the `index_todos_on_author_id` index

This deletes the `index_todos_on_author_id` index in the `todos` table
as the `index_todos_on_author_id_and_created_at` index supersedes it. We
can get some disk space back by removint the obsolete index.

Changelog: changed

db/post_migrate/20250304204818_delete_index_todos_on_author_id_and_created_at_index.rb

+# frozen_string_literal: true
+
+class DeleteIndexTodosOnAuthorIdAndCreatedAtIndex < Gitlab::Database::Migration[2.2]
+  disable_ddl_transaction!
+
+  milestone '17.10'
+
+  TABLE_NAME = :todos
+  INDEX_NAME = 'index_todos_on_author_id'
+
+  def up
+    remove_concurrent_index_by_name TABLE_NAME, name: INDEX_NAME
+  end
+
+  def down
+    add_concurrent_index TABLE_NAME, :author_id, name: INDEX_NAME
+  end
+end

db/schema_migrations/20250304204818

+b277f621aa5cc558f91d7357465d5efafbb81d30eb53ee1af7005ea96ff7cf01
\ No newline at end of file

db/structure.sql

@@ -35443,8 +35443,6 @@ CREATE INDEX index_timelogs_on_user_id ON timelogs USING btree (user_id);
 CREATE INDEX index_todos_coalesced_snoozed_until_created_at ON todos USING btree (user_id, state, timestamp_coalesce(snoozed_until, created_at));
-CREATE INDEX index_todos_on_author_id ON todos USING btree (author_id);
-
 CREATE INDEX index_todos_on_author_id_and_created_at ON todos USING btree (author_id, created_at);
 CREATE INDEX index_todos_on_commit_id ON todos USING btree (commit_id);

spec/support/helpers/database/duplicate_indexes.yml

@@ -91,9 +91,6 @@ taggings:
 term_agreements:
   term_agreements_unique_index:
   - index_term_agreements_on_user_id
-todos:
-  index_todos_on_author_id_and_created_at:
-  - index_todos_on_author_id
 work_item_hierarchy_restrictions:
   index_work_item_hierarchy_restrictions_on_parent_and_child:
   - index_work_item_hierarchy_restrictions_on_parent_type_id