sessionctx: support session var tidb_last_plan_replayer_token (#37851)

ref #37798

executor/executor_test.go

@@ -152,17 +152,18 @@ func TestPlanReplayer(t *testing.T) {
 	tk.MustExec("drop table if exists t")
 	tk.MustExec("create table t(a int, b int, index idx_a(a))")
 	tk.MustExec("alter table t set tiflash replica 1")
-	tk.MustExec("plan replayer dump explain select * from t where a=10")
-	tk.MustExec("plan replayer dump explain select /*+ read_from_storage(tiflash[t]) */ * from t")
+	tk.MustQuery("plan replayer dump explain select * from t where a=10")
+	tk.MustQuery("plan replayer dump explain select /*+ read_from_storage(tiflash[t]) */ * from t")
 
 	tk.MustExec("create table t1 (a int)")
 	tk.MustExec("create table t2 (a int)")
 	tk.MustExec("create definer=`root`@`127.0.0.1` view v1 as select * from t1")
 	tk.MustExec("create definer=`root`@`127.0.0.1` view v2 as select * from v1")
-	tk.MustExec("plan replayer dump explain with tmp as (select a from t1 group by t1.a) select * from tmp, t2 where t2.a=tmp.a;")
-	tk.MustExec("plan replayer dump explain select * from t1 where t1.a > (with cte1 as (select 1) select count(1) from cte1);")
-	tk.MustExec("plan replayer dump explain select * from v1")
-	tk.MustExec("plan replayer dump explain select * from v2")
+	tk.MustQuery("plan replayer dump explain with tmp as (select a from t1 group by t1.a) select * from tmp, t2 where t2.a=tmp.a;")
+	tk.MustQuery("plan replayer dump explain select * from t1 where t1.a > (with cte1 as (select 1) select count(1) from cte1);")
+	tk.MustQuery("plan replayer dump explain select * from v1")
+	tk.MustQuery("plan replayer dump explain select * from v2")
+	require.True(t, len(tk.Session().GetSessionVars().LastPlanReplayerToken) > 0)
 }
 
 func TestShow(t *testing.T) {

executor/plan_replayer.go

@@ -155,6 +155,7 @@ func (e *PlanReplayerExec) Next(ctx context.Context, req *chunk.Chunk) error {
 	}
 	req.AppendString(0, res)
 	e.endFlag = true
+	e.ctx.GetSessionVars().LastPlanReplayerToken = res
 	return nil
 }
 

server/plan_replayer_test.go

@@ -136,5 +136,13 @@ func prepareData4PlanReplayer(t *testing.T, client *testServerClient, statHandle
 	var filename string
 	err = rows.Scan(&filename)
 	require.NoError(t, err)
+	rows.Close()
+	rows = tk.MustQuery("select @@tidb_last_plan_replayer_token")
+	require.True(t, rows.Next(), "unexpected data")
+	var filename2 string
+	err = rows.Scan(&filename2)
+	require.NoError(t, err)
+	rows.Close()
+	require.Equal(t, filename, filename2)
 	return filename
 }

sessionctx/variable/session.go

@@ -1270,6 +1270,9 @@ type SessionVars struct {
 	// ranges would exceed the limit, it chooses less accurate ranges such as full range. 0 indicates that there is no
 	// memory limit for ranges.
 	RangeMaxSize int64
+
+	// LastPlanReplayerToken indicates the last plan replayer token
+	LastPlanReplayerToken string
 }
 
 // GetPreparedStmtByName returns the prepared statement specified by stmtName.

sessionctx/variable/sysvar.go

@@ -333,6 +333,11 @@ var defaultSysVars = []*SysVar{
 		}
 		return string(info), nil
 	}},
+	{Scope: ScopeSession, Name: TiDBLastPlanReplayerToken, Value: "", ReadOnly: true,
+		GetSession: func(s *SessionVars) (string, error) {
+			return s.LastPlanReplayerToken, nil
+		},
+	},
 	/* The system variables below have INSTANCE scope  */
 	{Scope: ScopeInstance, Name: TiDBLogFileMaxDays, Value: strconv.Itoa(config.GetGlobalConfig().Log.File.MaxDays), Type: TypeInt, MinValue: 0, MaxValue: math.MaxInt32, SetGlobal: func(s *SessionVars, val string) error {
 		maxAge, err := strconv.ParseInt(val, 10, 32)

sessionctx/variable/tidb_vars.go

@@ -90,6 +90,9 @@ const (
 	// TiDBLastDDLInfo is used to get the last ddl info within the current session.
 	TiDBLastDDLInfo = "tidb_last_ddl_info"
 
+	// TiDBLastPlanReplayerToken is used to get the last plan replayer token within the current session
+	TiDBLastPlanReplayerToken = "tidb_last_plan_replayer_token"
+
 	// TiDBConfig is a read-only variable that shows the config of the current server.
 	TiDBConfig = "tidb_config"