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Add MysqlGTIDSet.Add() and Minus() methods #667

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Merged
merged 2 commits into from
Jan 26, 2022
Merged

Add MysqlGTIDSet.Add() and Minus() methods #667

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9aaf95c
Add MysqlGTIDSet.Add() and Minus() methods
ostinru Jan 18, 2022
ecafb08
Merge branch 'master' into master
lance6716 Jan 25, 2022
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27 changes: 12 additions & 15 deletions mysql/mysql_gtid.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ import (
"encoding/binary"
"fmt"
"io"
"math"
"sort"
"strconv"
"strings"
Expand Down Expand Up @@ -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}
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I think we can

append minuend to n
check if i+1 out of range and append s.Intervals[i+1:]... to n

it's OK not to change

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There were 2 bugs in 50 lines :(
So, I would prefer not to increase cyclomatic complexity of this code and keep it as it in PR.

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wait @atercattus 's review as this function is complex

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Hi, @atercattus have you had a chance to look into this?

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(I'm going to merge this PR if he does not respond it tomorrow)

}

if minuend.Stop <= subtrahend.Start {
// no overlapping
Expand All @@ -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()
}

Expand Down
3 changes: 3 additions & 0 deletions mysql/mysql_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -177,6 +177,9 @@ 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", ""},
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found a failed case

		{"3E11FA47-71CA-11E1-9E33-C80AA9429562:20-21", "3E11FA47-71CA-11E1-9E33-C80AA9429562:21", "3E11FA47-71CA-11E1-9E33-C80AA9429562:20"},

please check it

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You right.

New version with changes:

  • merge 2 loops into one, so it will be easier to reason about
  • explicit IF conditions to make it clear which cases are handled in each branch

Hope, this time it is correct for all inputs

{"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 {
Expand Down