From 15803e386124e2545530d0d19fbd6e86b42c1903 Mon Sep 17 00:00:00 2001
From: lucklove <gnu.crazier@gmail.com>
Date: Mon, 23 Sep 2019 16:36:52 +0800
Subject: [PATCH] executor: fix unordered trace events in row format

The trace statement can print out a trace tree, however, in row
format, the tree is unordered, where earlier events may be placed
behind.

Signed-off-by: lucklove <gnu.crazier@gmail.com>
---
 executor/trace.go      | 13 +++++++++++++
 executor/trace_test.go | 17 +++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/executor/trace.go b/executor/trace.go
index 91acb341928c5..41744820642b7 100644
--- a/executor/trace.go
+++ b/executor/trace.go
@@ -17,6 +17,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"sort"
 	"time"
 
 	"github.com/opentracing/basictracer-go"
@@ -199,6 +200,18 @@ func dfsTree(t *appdash.Trace, prefix string, isLast bool, chk *chunk.Chunk) {
 	chk.AppendString(1, start.Format("15:04:05.000000"))
 	chk.AppendString(2, duration.String())
 
+	// Sort events by their start time
+	sort.Slice(t.Sub, func(i, j int) bool {
+		var istart, jstart time.Time
+		if ievent, err := t.Sub[i].TimespanEvent(); err == nil {
+			istart = ievent.Start()
+		}
+		if jevent, err := t.Sub[j].TimespanEvent(); err == nil {
+			jstart = jevent.Start()
+		}
+		return istart.Before(jstart)
+	})
+
 	for i, sp := range t.Sub {
 		dfsTree(sp, newPrefix, i == (len(t.Sub))-1 /*last element of array*/, chk)
 	}
diff --git a/executor/trace_test.go b/executor/trace_test.go
index fb2edfa687958..70bdcc35aa056 100644
--- a/executor/trace_test.go
+++ b/executor/trace_test.go
@@ -40,11 +40,28 @@ func (s *testSuite1) TestTraceExec(c *C) {
 	// +---------------------------+-----------------+------------+
 	rows = tk.MustQuery("trace format='row' select * from trace where id = 0;").Rows()
 	c.Assert(len(rows) > 1, IsTrue)
+	c.Assert(rowsOrdered(rows), IsTrue)
 
 	rows = tk.MustQuery("trace format='row' delete from trace where id = 0").Rows()
 	c.Assert(len(rows) > 1, IsTrue)
+	c.Assert(rowsOrdered(rows), IsTrue)
 
 	tk.MustExec("trace format='log' insert into trace (c1, c2, c3) values (1, 2, 3)")
 	rows = tk.MustQuery("trace format='log' select * from trace where id = 0;").Rows()
 	c.Assert(len(rows), GreaterEqual, 1)
 }
+
+func rowsOrdered(rows [][]interface{}) bool {
+	for idx := range rows {
+		if _, ok := rows[idx][1].(string); !ok {
+			return false
+		}
+		if idx == 0 {
+			continue
+		}
+		if rows[idx-1][1].(string) > rows[idx][1].(string) {
+			return false
+		}
+	}
+	return true
+}