*: clear delta info when roll back transaction (pingcap#5390)

executor/simple.go

@@ -127,6 +127,7 @@ func (e *SimpleExec) executeRollback(s *ast.RollbackStmt) error {
 	log.Infof("[%d] execute rollback statement", sessVars.ConnectionID)
 	sessVars.SetStatusFlag(mysql.ServerStatusInTrans, false)
 	if e.ctx.Txn().Valid() {
+		e.ctx.GetSessionVars().TxnCtx.ClearDelta()
 		return e.ctx.Txn().Rollback()
 	}
 	return nil

sessionctx/variable/session.go

@@ -100,6 +100,11 @@ func (tc *TransactionContext) UpdateDeltaForTable(tableID int64, delta int64, co
 	tc.TableDeltaMap[tableID] = item
 }
 
+// ClearDelta clears the delta map.
+func (tc *TransactionContext) ClearDelta() {
+	tc.TableDeltaMap = nil
+}
+
 // SessionVars is to handle user-defined or global variables in the current session.
 type SessionVars struct {
 	// UsersLock is a lock for user defined variables.

statistics/update_test.go

@@ -134,6 +134,29 @@ func (s *testStatsUpdateSuite) TestSingleSessionInsert(c *C) {
 	rs.Check(testkit.Rows("40", "70"))
 }
 
+func (s *testStatsUpdateSuite) TestRollback(c *C) {
+	defer cleanEnv(c, s.store, s.do)
+	testKit := testkit.NewTestKit(c, s.store)
+	testKit.MustExec("use test")
+	testKit.MustExec("create table t (a int, b int)")
+	testKit.MustExec("begin")
+	testKit.MustExec("insert into t values (1,2)")
+	testKit.MustExec("rollback")
+
+	is := s.do.InfoSchema()
+	tbl, err := is.TableByName(model.NewCIStr("test"), model.NewCIStr("t"))
+	c.Assert(err, IsNil)
+	tableInfo := tbl.Meta()
+	h := s.do.StatsHandle()
+	h.HandleDDLEvent(<-h.DDLEventCh())
+	h.DumpStatsDeltaToKV()
+	h.Update(is)
+
+	stats := h.GetTableStats(tableInfo.ID)
+	c.Assert(stats.Count, Equals, int64(0))
+	c.Assert(stats.ModifyCount, Equals, int64(0))
+}
+
 func (s *testStatsUpdateSuite) TestMultiSession(c *C) {
 	defer cleanEnv(c, s.store, s.do)
 	testKit := testkit.NewTestKit(c, s.store)