From 91c7ac1fb2e2338c9785632096cfcac79a6d80f2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20Jadwiszczak?=
 <michal.jadwiszczak@scylladb.com>
Date: Thu, 2 Apr 2026 09:54:54 +0200
Subject: [PATCH] view_building_worker: execute drain() once

Future changes will require that the view building worker is drained
only once per its lifetime.
---
 db/view/view_building_worker.cc | 8 ++++++++
 db/view/view_building_worker.hh | 5 +++++
 2 files changed, 13 insertions(+)

diff --git a/db/view/view_building_worker.cc b/db/view/view_building_worker.cc
index 813707f348..3235797c12 100644
--- a/db/view/view_building_worker.cc
+++ b/db/view/view_building_worker.cc
@@ -143,6 +143,14 @@ dht::token_range view_building_worker::get_tablet_token_range(table_id table_id,
 }
 
 future<> view_building_worker::drain() {
+    auto drain_started = std::exchange(_drain_started, started_drain::yes);
+    if (drain_started == started_drain::no) {
+        _drain_finished = shared_future(do_drain());
+    }
+    return _drain_finished.get_future();
+}
+
+future<> view_building_worker::do_drain() {
     if (!_as.abort_requested()) {
         _as.request_abort();
     }
diff --git a/db/view/view_building_worker.hh b/db/view/view_building_worker.hh
index 66718d8c67..f420f0d882 100644
--- a/db/view/view_building_worker.hh
+++ b/db/view/view_building_worker.hh
@@ -177,6 +177,11 @@ private:
     void init_messaging_service();
     future<> uninit_messaging_service();
     future<std::vector<utils::UUID>> work_on_tasks(raft::term_t term, std::vector<utils::UUID> ids);
+
+    using started_drain = bool_class<struct started_drain_tag>;
+    started_drain _drain_started = started_drain::no;
+    shared_future<> _drain_finished;
+    future<> do_drain();
 };
 
 }