executor: make the format of the DB field in slow ... (#18389) (#18512)

pingcap · Sep 4, 2020 · 709b48a · 709b48a
1 parent a5922c2
commit 709b48a
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Showing 5 changed files with 31 additions and 8 deletions.
diff --git a/executor/simple.go b/executor/simple.go
@@ -523,6 +523,7 @@ func (e *SimpleExec) executeUse(s *ast.UseStmt) error {
 	if !exists {
 		return infoschema.ErrDatabaseNotExists.GenWithStackByArgs(dbname)
 	}
+	e.ctx.GetSessionVars().CurrentDBChanged = dbname.O != e.ctx.GetSessionVars().CurrentDB
 	e.ctx.GetSessionVars().CurrentDB = dbname.O
 	// character_set_database is the character set used by the default database.
 	// The server sets this variable whenever the default database changes.

diff --git a/executor/slow_query.go b/executor/slow_query.go
@@ -260,6 +260,13 @@ func (e *slowQueryRetriever) parseSlowLog(ctx sessionctx.Context, reader *bufio.
 					}
 				}
 			} else if strings.HasSuffix(line, variable.SlowLogSQLSuffixStr) {
+				if strings.HasPrefix(line, "use") {
+					// `use DB` statements in the slow log is used to keep it be compatible with MySQL,
+					// since we already get the current DB from the `# DB` field, we can ignore it here,
+					// please see https://github.com/pingcap/tidb/issues/17846 for more details.
+					continue
+				}
+
 				// Get the sql string, and mark the start flag to false.
 				_, err = st.setFieldValue(tz, variable.SlowLogQuerySQLStr, string(hack.Slice(line)), e.fileLine, e.checker)
 				if err != nil {

diff --git a/executor/slow_query_test.go b/executor/slow_query_test.go
@@ -60,6 +60,7 @@ func (s *testExecSuite) TestParseSlowLogFile(c *C) {
 # Succ: false
 # Plan_digest: 60e9378c746d9a2be1c791047e008967cf252eb6de9167ad3aa6098fa2d523f4
 # Prev_stmt: update t set i = 1;
+use test;
 select * from t;`
 	reader := bufio.NewReader(bytes.NewBufferString(slowLogStr))
 	loc, err := time.LoadLocation("Asia/Shanghai")

diff --git a/sessionctx/variable/session.go b/sessionctx/variable/session.go
@@ -373,6 +373,10 @@ type SessionVars struct {
 	// CurrentDB is the default database of this session.
 	CurrentDB string
 
+	// CurrentDBChanged indicates if the CurrentDB has been updated, and if it is we should print it into
+	// the slow log to make it be compatible with MySQL, https://github.com/pingcap/tidb/issues/17846.
+	CurrentDBChanged bool
+
 	// StrictSQLMode indicates if the session is in strict mode.
 	StrictSQLMode bool
 
@@ -1786,6 +1790,11 @@ func (s *SessionVars) SlowLogFormat(logItems *SlowQueryLogItems) string {
 		writeSlowLogItem(&buf, SlowLogPrevStmt, logItems.PrevStmt)
 	}
 
+	if s.CurrentDBChanged {
+		buf.WriteString(fmt.Sprintf("use %s;\n", s.CurrentDB))
+		s.CurrentDBChanged = false
+	}
+
 	buf.WriteString(logItems.SQL)
 	if len(logItems.SQL) == 0 || logItems.SQL[len(logItems.SQL)-1] != ';' {
 		buf.WriteString(";")

diff --git a/sessionctx/variable/session_test.go b/sessionctx/variable/session_test.go
@@ -175,7 +175,7 @@ func (*testSessionSuite) TestSlowLogFormat(c *C) {
 
 	var memMax int64 = 2333
 	var diskMax int64 = 6666
-	resultString := `# Txn_start_ts: 406649736972468225
+	resultFields := `# Txn_start_ts: 406649736972468225
 # User@Host: root[root] @ 192.168.0.1 [192.168.0.1]
 # Conn_ID: 1
 # Query_time: 1
@@ -186,7 +186,7 @@ func (*testSessionSuite) TestSlowLogFormat(c *C) {
 # DB: test
 # Index_names: [t1:a,t2:b]
 # Is_internal: true
-# Digest: 42a1c8aae6f133e934d4bf0147491709a8812ea05ff8819ec522780fe657b772
+# Digest: f94c76d7fa8f60e438118752bfbfb71fe9e1934888ac415ddd8625b121af124c
 # Stats: t1:pseudo
 # Num_cop_tasks: 10
 # Cop_proc_avg: 1 Cop_proc_p90: 2 Cop_proc_max: 3 Cop_proc_addr: 10.6.131.78
@@ -203,11 +203,10 @@ func (*testSessionSuite) TestSlowLogFormat(c *C) {
 # PD_total: 11
 # Backoff_total: 12
 # Write_sql_response_total: 1
-# Succ: true
-select * from t;`
-	sql := "select * from t"
+# Succ: true`
+	sql := "select * from t;"
 	_, digest := parser.NormalizeDigest(sql)
-	logString := seVar.SlowLogFormat(&variable.SlowQueryLogItems{
+	logItems := &variable.SlowQueryLogItems{
 		TxnTS:             txnTS,
 		SQL:               sql,
 		Digest:            digest,
@@ -233,8 +232,14 @@ select * from t;`
 			DurationPreprocessSubQuery: 2,
 			PreprocessSubQueries:       2,
 		},
-	})
-	c.Assert(logString, Equals, resultString)
+	}
+	logString := seVar.SlowLogFormat(logItems)
+	c.Assert(logString, Equals, resultFields+"\n"+sql)
+
+	seVar.CurrentDBChanged = true
+	logString = seVar.SlowLogFormat(logItems)
+	c.Assert(logString, Equals, resultFields+"\n"+"use test;\n"+sql)
+	c.Assert(seVar.CurrentDBChanged, IsFalse)
 }
 
 func (*testSessionSuite) TestIsolationRead(c *C) {