From 38bd1ccf4250ab07c75277edbd818cddbab75373 Mon Sep 17 00:00:00 2001
From: MATSUU Takuto <matsuu@gmail.com>
Date: Mon, 20 Jun 2022 22:47:03 +0900
Subject: [PATCH 1/2] replace io.ReadSeeker with io.Reader

---
 log/slow/parser.go | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/log/slow/parser.go b/log/slow/parser.go
index 4db2469..266c4df 100644
--- a/log/slow/parser.go
+++ b/log/slow/parser.go
@@ -60,7 +60,7 @@ var (
 
 // SlowLogParser parses a MySQL slow log. It implements the LogParser interface.
 type SlowLogParser struct {
-	reader io.ReadSeeker
+	reader io.Reader
 	opt    log.Options
 	// --
 	stopChan    chan bool
@@ -77,7 +77,7 @@ type SlowLogParser struct {
 }
 
 // NewSlowLogParser returns a new SlowLogParser that reads from the open file.
-func NewSlowLogParser(r io.ReadSeeker, opt log.Options) *SlowLogParser {
+func NewSlowLogParser(r io.Reader, opt log.Options) *SlowLogParser {
 	if opt.DefaultLocation == nil {
 		// Old MySQL format assumes time is taken from SYSTEM.
 		opt.DefaultLocation = time.Local
@@ -129,8 +129,14 @@ func (p *SlowLogParser) Start() error {
 	// Seek to the offset, if any.
 	// @todo error if start off > file size
 	if p.opt.StartOffset > 0 {
-		if _, err := p.reader.Seek(int64(p.opt.StartOffset), os.SEEK_SET); err != nil {
-			return err
+		if reader, ok := p.reader.(io.ReadSeeker); ok {
+			if _, err := reader.Seek(int64(p.opt.StartOffset), os.SEEK_SET); err != nil {
+				return err
+			}
+		} else {
+			if _, err := io.CopyN(io.Discard, p.reader, int64(p.opt.StartOffset)); err != nil {
+				return err
+			}
 		}
 	}
 

From 4ccbe9051c47d46adc5de62eda678a0445c25bdb Mon Sep 17 00:00:00 2001
From: MATSUU Takuto <matsuu@gmail.com>
Date: Mon, 20 Jun 2022 22:47:45 +0900
Subject: [PATCH 2/2] add test for parsing log from io.MultiReader

---
 log/slow/parser_test.go | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/log/slow/parser_test.go b/log/slow/parser_test.go
index 1b0ea79..873b8ab 100644
--- a/log/slow/parser_test.go
+++ b/log/slow/parser_test.go
@@ -32,6 +32,7 @@ package slow_test
 
 import (
 	"bytes"
+	"io"
 	l "log"
 	"os"
 	"path"
@@ -1953,3 +1954,27 @@ SELECT fruit FROM trees;
 
 	assert.NotEqual(t, 0, len(got))
 }
+
+func TestParseFromMultiReader(t *testing.T) {
+	query1 := `
+# Time: 071218 11:48:27
+# User@Host: [SQL_SLAVE] @  []
+# Thread_id: 3  Schema: db1
+# Query_time: 0.000012  Lock_time: 0.000000  Rows_sent: 0  Rows_examined: 0`
+	query2 := `
+use db2;
+SELECT fruit FROM trees;
+`
+
+	buf1 := bytes.NewReader([]byte(query1))
+	buf2 := bytes.NewReader([]byte(query2))
+	p := parser.NewSlowLogParser(io.MultiReader(buf1, buf2), opt)
+
+	got := []log.Event{}
+	go p.Start()
+	for e := range p.EventChan() {
+		got = append(got, *e)
+	}
+
+	assert.NotEqual(t, 0, len(got))
+}