session: fix set session variable make tidb_snapshot unwork (#28677) (#…

…28683)
pingcap · Oct 19, 2021 · da1c21f · da1c21f
1 parent 333edd8
commit da1c21f
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Showing 2 changed files with 29 additions and 2 deletions.
diff --git a/executor/set.go b/executor/set.go
@@ -181,7 +181,7 @@ func (e *SetExecutor) setSysVariable(ctx context.Context, name string, v *expres
  }
  }
 
- err = e.loadSnapshotInfoSchemaIfNeeded(newSnapshotTS)
+ err = e.loadSnapshotInfoSchemaIfNeeded(name, newSnapshotTS)
  if err != nil {
  fallbackOldSnapshotTS()
  return err
@@ -254,7 +254,10 @@ func (e *SetExecutor) getVarValue(v *expression.VarAssignment, sysVar *variable.
  return nativeVal.ToString()
 }
 
-func (e *SetExecutor) loadSnapshotInfoSchemaIfNeeded(snapshotTS uint64) error {
+func (e *SetExecutor) loadSnapshotInfoSchemaIfNeeded(name string, snapshotTS uint64) error {
+ if name != variable.TiDBSnapshot && name != variable.TiDBTxnReadTS {
+ return nil
+ }
  vars := e.ctx.GetSessionVars()
  if snapshotTS == 0 {
  vars.SnapshotInfoschema = nil

diff --git a/session/session_test.go b/session/session_test.go
@@ -5575,3 +5575,27 @@ func (s *testSessionSuite) TestLocalTemporaryTableUpdate(c *C) {
  tk.MustQuery("select * from tmp1").Check(testkit.Rows())
  }
 }
+
+func (s *testSessionSuite) TestFixSetTiDBSnapshotTS(c *C) {
+ tk := testkit.NewTestKit(c, s.store)
+ safePointName := "tikv_gc_safe_point"
+ safePointValue := "20160102-15:04:05 -0700"
+ safePointComment := "All versions after safe point can be accessed. (DO NOT EDIT)"
+ updateSafePoint := fmt.Sprintf(`INSERT INTO mysql.tidb VALUES ('%[1]s', '%[2]s', '%[3]s')
+ ON DUPLICATE KEY
+ UPDATE variable_value = '%[2]s', comment = '%[3]s'`, safePointName, safePointValue, safePointComment)
+ tk.MustExec(updateSafePoint)
+ tk.MustExec("create database t123")
+ time.Sleep(time.Second)
+ ts := time.Now().Format("2006-1-2 15:04:05")
+ time.Sleep(time.Second)
+ tk.MustExec("drop database t123")
+ err := tk.ExecToErr("use t123")
+ c.Assert(err, NotNil)
+ c.Assert(err.Error(), Matches, ".*Unknown database.*")
+ tk.MustExec(fmt.Sprintf("set @@tidb_snapshot='%s'", ts))
+ tk.MustExec("use t123")
+ // update any session variable and assert whether infoschema is changed
+ tk.MustExec("SET SESSION sql_mode = 'STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER';")
+ tk.MustExec("use t123")
+}