From 9aaf95c0eb3d154bce19edb4ccfbba89ca49231d Mon Sep 17 00:00:00 2001
From: Nikolai Antonov <ostinru@yandex-team.ru>
Date: Tue, 18 Jan 2022 22:29:30 +0300
Subject: [PATCH] Add MysqlGTIDSet.Add() and Minus() methods  * fix off-by-one
 error

---
 mysql/mysql_gtid.go | 27 ++++++++++++---------------
 mysql/mysql_test.go |  3 +++
 2 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/mysql/mysql_gtid.go b/mysql/mysql_gtid.go
index 2a10ae257..623278281 100644
--- a/mysql/mysql_gtid.go
+++ b/mysql/mysql_gtid.go
@@ -5,6 +5,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"io"
+	"math"
 	"sort"
 	"strconv"
 	"strings"
@@ -234,11 +235,15 @@ func (s *UUIDSet) MinusInterval(in IntervalSlice) {
 	i, j := 0, 0
 	var minuend Interval
 	var subtrahend Interval
-	for j < len(in) && i < len(s.Intervals) {
+	for i < len(s.Intervals) {
 		if minuend.Stop != s.Intervals[i].Stop { // `i` changed?
 			minuend = s.Intervals[i]
 		}
-		subtrahend = in[j]
+		if j < len(in) {
+			subtrahend = in[j]
+		} else {
+			subtrahend = Interval{math.MaxInt64, math.MaxInt64}
+		}
 
 		if minuend.Stop <= subtrahend.Start {
 			// no overlapping
@@ -248,33 +253,25 @@ func (s *UUIDSet) MinusInterval(in IntervalSlice) {
 			// no overlapping
 			j++
 		} else {
-			if minuend.Start < subtrahend.Start && minuend.Stop < subtrahend.Stop {
+			if minuend.Start < subtrahend.Start && minuend.Stop <= subtrahend.Stop {
 				n = append(n, Interval{minuend.Start, subtrahend.Start})
 				i++
-			} else if minuend.Start > subtrahend.Start && minuend.Stop > subtrahend.Stop {
+			} else if minuend.Start >= subtrahend.Start && minuend.Stop > subtrahend.Stop {
 				minuend = Interval{subtrahend.Stop, minuend.Stop}
 				j++
 			} else if minuend.Start >= subtrahend.Start && minuend.Stop <= subtrahend.Stop {
 				// minuend is completely removed
 				i++
-			} else {
+			} else if minuend.Start < subtrahend.Start && minuend.Stop > subtrahend.Stop {
 				n = append(n, Interval{minuend.Start, subtrahend.Start})
 				minuend = Interval{subtrahend.Stop, minuend.Stop}
 				j++
+			} else {
+				panic("should never be here")
 			}
 		}
 	}
 
-	lastSub := in[len(in)-1]
-	for ; i < len(s.Intervals); i++ {
-		minuend = s.Intervals[i]
-		if minuend.Start < lastSub.Stop {
-			n = append(n, Interval{lastSub.Stop, minuend.Stop})
-		} else {
-			n = append(n, s.Intervals[i])
-		}
-	}
-
 	s.Intervals = n.Normalize()
 }
 
diff --git a/mysql/mysql_test.go b/mysql/mysql_test.go
index 62b24f758..ca7172ffe 100644
--- a/mysql/mysql_test.go
+++ b/mysql/mysql_test.go
@@ -180,6 +180,9 @@ func (t *mysqlTestSuite) TestMysqlGTIDMinus(c *check.C) {
 		{"3E11FA47-71CA-11E1-9E33-C80AA9429562:20-57:60-90", "3E11FA47-71CA-11E1-9E33-C80AA9429562:23", "3E11FA47-71CA-11E1-9E33-C80AA9429562:20-22:24-57:60-90"},
 		{"3E11FA47-71CA-11E1-9E33-C80AA9429562:20-57:60-90", "3E11FA47-71CA-11E1-9E33-C80AA9429562:22-70", "3E11FA47-71CA-11E1-9E33-C80AA9429562:20-21:71-90"},
 		{"3E11FA47-71CA-11E1-9E33-C80AA9429562:28-57", "3E11FA47-71CA-11E1-9E33-C80AA9429562:28-57", ""},
+		{"3E11FA47-71CA-11E1-9E33-C80AA9429562:20-21", "3E11FA47-71CA-11E1-9E33-C80AA9429562:21", "3E11FA47-71CA-11E1-9E33-C80AA9429562:20"},
+		{"582A11ED-786C-11EC-ACCC-E0356662B76E:1-209692", "582A11ED-786C-11EC-ACCC-E0356662B76E:1-146519", "582A11ED-786C-11EC-ACCC-E0356662B76E:146520-209692"},
+		{"582A11ED-786C-11EC-ACCC-E0356662B76E:1-209692", "582A11ED-786C-11EC-ACCC-E0356662B76E:2-146519", "582A11ED-786C-11EC-ACCC-E0356662B76E:1:146520-209692"},
 	}
 
 	for _, tc := range testCases {