executor,infoschema: Change column type on information_schema.CLUSTER_INFO

executor/infoschema_reader.go

@@ -1467,11 +1467,11 @@ func (e *memtableRetriever) dataForTiDBClusterInfo(ctx sessionctx.Context) error
 	}
 	rows := make([][]types.Datum, 0, len(servers))
 	for _, server := range servers {
-		startTimeStr := ""
 		upTimeStr := ""
+		startTimeNative := types.NewTime(types.FromDate(0, 0, 0, 0, 0, 0, 0), mysql.TypeDatetime, 0)
 		if server.StartTimestamp > 0 {
 			startTime := time.Unix(server.StartTimestamp, 0)
-			startTimeStr = startTime.Format(time.RFC3339)
+			startTimeNative = types.NewTime(types.FromGoTime(startTime), mysql.TypeDatetime, 0)
 			upTimeStr = time.Since(startTime).String()
 		}
 		row := types.MakeDatums(
@@ -1480,7 +1480,7 @@ func (e *memtableRetriever) dataForTiDBClusterInfo(ctx sessionctx.Context) error
 			server.StatusAddr,
 			server.Version,
 			server.GitHash,
-			startTimeStr,
+			startTimeNative,
 			upTimeStr,
 			server.ServerID,
 		)

infoschema/tables.go

@@ -1113,7 +1113,7 @@ var tableClusterInfoCols = []columnInfo{
 	{name: "STATUS_ADDRESS", tp: mysql.TypeVarchar, size: 64},
 	{name: "VERSION", tp: mysql.TypeVarchar, size: 64},
 	{name: "GIT_HASH", tp: mysql.TypeVarchar, size: 64},
-	{name: "START_TIME", tp: mysql.TypeVarchar, size: 32},
+	{name: "START_TIME", tp: mysql.TypeDatetime, size: 19},
 	{name: "UPTIME", tp: mysql.TypeVarchar, size: 32},
 	{name: "SERVER_ID", tp: mysql.TypeLonglong, size: 21, comment: "invalid if the configuration item `enable-global-kill` is set to FALSE"},
 }