ui, server: update cluster settings to include last update time

Resolves cockroachdb#76626

Previously it was difficult to determine from the cluster
settings page which settings have been altered.
This patch updates the cluster settings endpoint to include a
last updated field, indicating when the setting was last altered,
which allows the settings page to include that column in the
table and is pre-sorted by this value.

Release justification: Fairly minor changes for QoL upgrade
Release note: None

docs/generated/http/full.md

@@ -5019,6 +5019,7 @@ SettingsResponse is the response to SettingsRequest.
 | type | [string](#cockroach.server.serverpb.SettingsResponse-string) |  |  | [reserved](#support-status) |
 | description | [string](#cockroach.server.serverpb.SettingsResponse-string) |  |  | [reserved](#support-status) |
 | public | [bool](#cockroach.server.serverpb.SettingsResponse-bool) |  |  | [reserved](#support-status) |
+| last_updated | [google.protobuf.Timestamp](#cockroach.server.serverpb.SettingsResponse-google.protobuf.Timestamp) |  |  | [reserved](#support-status) |
 
 
 

pkg/server/admin.go

@@ -1686,21 +1686,50 @@ func (s *adminServer) Settings(
 		lookupPurpose = settings.LookupForReporting
 	}
 
+	// Read the system.settings table to determine the settings for which we have
+	// explicitly set values -- the in-memory SV has the set and default values
+	// flattened for quick reads, but we'd only need the non-defaults for comparison.
+	alteredSettings := make(map[string]*time.Time)
+	if it, err := s.server.sqlServer.internalExecutor.QueryIteratorEx(
+		ctx, "read-setting", nil, /* txn */
+		sessiondata.InternalExecutorOverride{User: security.RootUserName()},
+		`SELECT name, "lastUpdated" FROM system.settings`,
+	); err != nil {
+		log.Warningf(ctx, "failed to read settings: %s", err)
+	} else {
+		var ok bool
+		for ok, err = it.Next(ctx); ok; ok, err = it.Next(ctx) {
+			row := it.Cur()
+			name := string(tree.MustBeDString(row[0]))
+			lastUpdated := row[1].(*tree.DTimestamp)
+			alteredSettings[name] = &lastUpdated.Time
+		}
+		if err != nil {
+			// No need to clear AlteredSettings map since we only make best
+			// effort to populate it.
+			log.Warningf(ctx, "failed to read settings: %s", err)
+		}
+	}
+
 	resp := serverpb.SettingsResponse{KeyValues: make(map[string]serverpb.SettingsResponse_Value)}
 	for _, k := range keys {
 		v, ok := settings.Lookup(k, lookupPurpose)
 		if !ok {
 			continue
 		}
+		var altered *time.Time
+		if val, ok := alteredSettings[k]; ok {
+			altered = val
+		}
 		resp.KeyValues[k] = serverpb.SettingsResponse_Value{
 			Type: v.Typ(),
 			// Note: v.String() redacts the values if the purpose is not "LocalAccess".
 			Value:       v.String(&s.server.st.SV),
 			Description: v.Description(),
 			Public:      v.Visibility() == settings.Public,
+			LastUpdated: altered,
 		}
 	}
-
 	return &resp, nil
 }
 

pkg/server/admin_test.go

@@ -1062,7 +1062,7 @@ func TestAdminAPISettings(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	defer log.Scope(t).Close(t)
 
-	s, _, _ := serverutils.StartServer(t, base.TestServerArgs{})
+	s, conn, _ := serverutils.StartServer(t, base.TestServerArgs{})
 	defer s.Stopper().Stop(context.Background())
 
 	// Any bool that defaults to true will work here.
@@ -1097,6 +1097,20 @@ func TestAdminAPISettings(t *testing.T) {
 		if typ != v.Type {
 			t.Errorf("%s: expected type %s, got %s", k, typ, v.Type)
 		}
+		if v.LastUpdated != nil {
+			db := sqlutils.MakeSQLRunner(conn)
+			q := makeSQLQuery()
+			q.Append(`SELECT name, "lastUpdated" FROM system.settings WHERE name=$`, k)
+			rows := db.Query(
+				t,
+				q.String(),
+				q.QueryArguments()...,
+			)
+			defer rows.Close()
+			if rows.Next() == false {
+				t.Errorf("missing sql row for %s", k)
+			}
+		}
 	}
 
 	t.Run("all", func(t *testing.T) {