From 66b3fc4e2c259ee88ad93c94f1645bb401a120fb Mon Sep 17 00:00:00 2001
From: Gleb Natapov <gleb@scylladb.com>
Date: Wed, 25 Mar 2026 12:46:30 +0200
Subject: [PATCH] db/system_distributed_keyspace: drop CDC_TOPOLOGY_DESCRIPTION
 and CDC_GENERATIONS_V2

They are used only to prevent permission change, but since tables are
unused even if they exists there is no problem changing their
permissions, so no point keeping the definitions just for that.
---
 db/system_distributed_keyspace.hh | 7 -------
 service/client_state.cc           | 4 +---
 test/boost/cdc_test.cc            | 6 +-----
 3 files changed, 2 insertions(+), 15 deletions(-)

diff --git a/db/system_distributed_keyspace.hh b/db/system_distributed_keyspace.hh
index c21ad398c1..4e07fcd619 100644
--- a/db/system_distributed_keyspace.hh
+++ b/db/system_distributed_keyspace.hh
@@ -39,13 +39,6 @@ public:
 
     static constexpr auto VIEW_BUILD_STATUS = "view_build_status";
 
-    /* Nodes use this table to communicate new CDC stream generations to other nodes. */
-    static constexpr auto CDC_TOPOLOGY_DESCRIPTION = "cdc_generation_descriptions";
-
-    /* Nodes use this table to communicate new CDC stream generations to other nodes.
-     * Resides in system_distributed_everywhere. */
-    static constexpr auto CDC_GENERATIONS_V2 = "cdc_generation_descriptions_v2";
-
     /* This table is used by CDC clients to learn about available CDC streams. */
     static constexpr auto CDC_DESC_V2 = "cdc_streams_descriptions_v2";
 
diff --git a/service/client_state.cc b/service/client_state.cc
index 30cc254ef0..667d6eb163 100644
--- a/service/client_state.cc
+++ b/service/client_state.cc
@@ -124,9 +124,7 @@ future<> service::client_state::check_internal_table_permissions(std::string_vie
     if (forbidden_permissions.contains(cmd.permission)) {
         if ((ks == db::system_distributed_keyspace::NAME || ks == db::system_distributed_keyspace::NAME_EVERYWHERE)
                 && (table_name == db::system_distributed_keyspace::CDC_DESC_V2
-                || table_name == db::system_distributed_keyspace::CDC_TOPOLOGY_DESCRIPTION
-                || table_name == db::system_distributed_keyspace::CDC_TIMESTAMPS
-                || table_name == db::system_distributed_keyspace::CDC_GENERATIONS_V2)) {
+                || table_name == db::system_distributed_keyspace::CDC_TIMESTAMPS)) {
             return make_exception_future(exceptions::unauthorized_exception(
                     format("Cannot {} {}", auth::permissions::to_string(cmd.permission), cmd.resource)));
         }
diff --git a/test/boost/cdc_test.cc b/test/boost/cdc_test.cc
index d11075f9fc..e8c175a831 100644
--- a/test/boost/cdc_test.cc
+++ b/test/boost/cdc_test.cc
@@ -297,11 +297,10 @@ SEASTAR_THREAD_TEST_CASE(test_permissions_of_cdc_description) {
             BOOST_REQUIRE_THROW(e.execute_cql(stmt).get(), exceptions::unauthorized_exception);
         };
 
-        const std::string generations_v2 = "system_distributed_everywhere.cdc_generation_descriptions_v2";
         const std::string streams = "system_distributed.cdc_streams_descriptions_v2";
         const std::string timestamps = "system_distributed.cdc_generation_timestamps";
 
-        for (auto& t : {generations_v2, streams, timestamps}) {
+        for (auto& t : {streams, timestamps}) {
             auto dot_pos = t.find_first_of('.');
             SCYLLA_ASSERT(dot_pos != std::string_view::npos && dot_pos != 0 && dot_pos != t.size() - 1);
             BOOST_REQUIRE(e.local_db().has_schema(t.substr(0, dot_pos), t.substr(dot_pos + 1)));
@@ -317,18 +316,15 @@ SEASTAR_THREAD_TEST_CASE(test_permissions_of_cdc_description) {
         for (auto& t : {streams}) {
             assert_unauthorized(seastar::format("ALTER TABLE {} ALTER time TYPE blob", t));
         }
-        assert_unauthorized(seastar::format("ALTER TABLE {} ALTER id TYPE blob", generations_v2));
         assert_unauthorized(seastar::format("ALTER TABLE {} ALTER key TYPE blob", timestamps));
 
         // Allow DELETE
         for (auto& t : {streams}) {
             e.execute_cql(seastar::format("DELETE FROM {} WHERE time = toTimeStamp(now())", t)).get();
         }
-        e.execute_cql(seastar::format("DELETE FROM {} WHERE id = uuid()", generations_v2)).get();
         e.execute_cql(seastar::format("DELETE FROM {} WHERE key = 'timestamps'", timestamps)).get();
 
         // Allow UPDATE, INSERT
-        e.execute_cql(seastar::format("INSERT INTO {} (id, range_end) VALUES (uuid(), 0)", generations_v2)).get();
         e.execute_cql(seastar::format("INSERT INTO {} (time, range_end) VALUES (toTimeStamp(now()), 0)", streams)).get();
         e.execute_cql(seastar::format("UPDATE {} SET expired = toTimeStamp(now()) WHERE key = 'timestamps' AND time = toTimeStamp(now())", timestamps)).get();
     }).get();