From 5da01297752522d57a7ea68a628453ea5da29b90 Mon Sep 17 00:00:00 2001
From: Calle Wilund <calle@scylladb.com>
Date: Wed, 3 Mar 2021 15:44:54 +0000
Subject: [PATCH] system_distributed_keyspace: Add better routine to get latest
 cdc gen. timestamp

Since we have a table of cdc version timestamps, conviniently sorted
reversed, we can just query this and get the latest known gen ts.
---
 db/system_distributed_keyspace.cc | 12 ++++++++++++
 db/system_distributed_keyspace.hh |  3 +++
 2 files changed, 15 insertions(+)

diff --git a/db/system_distributed_keyspace.cc b/db/system_distributed_keyspace.cc
index f872a7f099..f037ac1078 100644
--- a/db/system_distributed_keyspace.cc
+++ b/db/system_distributed_keyspace.cc
@@ -525,6 +525,18 @@ system_distributed_keyspace::cdc_get_versioned_streams(db_clock::time_point not_
     co_return result;
 }
 
+future<db_clock::time_point> 
+system_distributed_keyspace::cdc_current_generation_timestamp(context ctx) {
+    auto timestamp_cql = co_await _qp.execute_internal(
+            format("SELECT time FROM {}.{} WHERE key = ? limit 1", NAME, CDC_TIMESTAMPS),
+            quorum_if_many(ctx.num_token_owners),
+            internal_distributed_query_state(),
+            { CDC_TIMESTAMPS_KEY },
+            false);
+
+    co_return timestamp_cql->one().get_as<db_clock::time_point>("time");
+}
+
 future<std::vector<db_clock::time_point>>
 system_distributed_keyspace::get_cdc_desc_v1_timestamps(context ctx) {
     std::vector<db_clock::time_point> res;
diff --git a/db/system_distributed_keyspace.hh b/db/system_distributed_keyspace.hh
index cf434749d5..7be342df60 100644
--- a/db/system_distributed_keyspace.hh
+++ b/db/system_distributed_keyspace.hh
@@ -109,6 +109,9 @@ public:
     future<std::vector<db_clock::time_point>> get_cdc_desc_v1_timestamps(context);
 
     future<std::map<db_clock::time_point, cdc::streams_version>> cdc_get_versioned_streams(db_clock::time_point not_older_than, context);
+
+    future<db_clock::time_point> cdc_current_generation_timestamp(context);
+
 };
 
 }