cherry pick pingcap#20000 to release-4.0

Signed-off-by: ti-srebot <[email protected]>

executor/executor_test.go

@@ -5910,7 +5910,25 @@ func (s *testSuite) TestGenerateColumnReplace(c *C) {
 	tk.MustQuery("select * from t1").Check(testkit.Rows("3 4"))
 }
 
+<<<<<<< HEAD
 func (s *testSuite) TestSlowQuerySensitiveQuery(c *C) {
+=======
+func (s *testSlowQuery) TestSlowQueryWithoutSlowLog(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	originCfg := config.GetGlobalConfig()
+	newCfg := *originCfg
+	newCfg.Log.SlowQueryFile = "tidb-slow-not-exist.log"
+	newCfg.Log.SlowThreshold = math.MaxUint64
+	config.StoreGlobalConfig(&newCfg)
+	defer func() {
+		config.StoreGlobalConfig(originCfg)
+	}()
+	tk.MustQuery("select query from information_schema.slow_query").Check(testkit.Rows())
+	tk.MustQuery("select query from information_schema.slow_query where time > '2020-09-15 12:16:39' and time < now()").Check(testkit.Rows())
+}
+
+func (s *testSlowQuery) TestSlowQuerySensitiveQuery(c *C) {
+>>>>>>> aed24e4... executor: fix query slow_query error when slow-log file not exist (#20000)
 	tk := testkit.NewTestKit(c, s.store)
 	originCfg := config.GetGlobalConfig()
 	newCfg := *originCfg

executor/slow_query.go

@@ -618,6 +618,9 @@ func (e *slowQueryRetriever) getAllFiles(sctx sessionctx.Context, logFilePath st
 	if e.extractor == nil || !e.extractor.Enable {
 		file, err := os.Open(logFilePath)
 		if err != nil {
+			if os.IsNotExist(err) {
+				return nil, nil
+			}
 			return nil, err
 		}
 		return []logFile{{file: file}}, nil