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Fix binlog file lexographical comparison #18

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grodowski wants to merge 2 commits into from
+21 −15
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Fix binlog file lexographical comparison #18

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fc00059
Parse binlog file numbers numerically instead of lexicographically to…
grodowski Nov 6, 2025
d2ee83c
Remove unused fn FileBinlogCoordinates.FileSmallerThan
grodowski Nov 6, 2025
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20 changes: 5 additions & 15 deletions go/mysql/binlog_file.go
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Original file line number Diff line number Diff line change
Expand Up @@ -78,13 +78,12 @@ func (this *FileBinlogCoordinates) SmallerThan(other BinlogCoordinates) bool {
if !ok || other == nil {
return false
}
if this.LogFile < coord.LogFile {
return true
}
if this.LogFile == coord.LogFile && this.LogPos < coord.LogPos {
return true

fileNumberDist := this.FileNumberDistance(coord)
if fileNumberDist == 0 {
return this.LogPos < coord.LogPos
}
return false
return fileNumberDist > 0
}

// SmallerThanOrEquals returns true if this coordinate is the same or equal to the other one.
Expand All @@ -100,15 +99,6 @@ func (this *FileBinlogCoordinates) SmallerThanOrEquals(other BinlogCoordinates)
return this.LogFile == coord.LogFile && this.LogPos == coord.LogPos // No Type comparison
}

// FileSmallerThan returns true if this coordinate's file is strictly smaller than the other's.
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@coding-chimp coding-chimp Nov 6, 2025

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Was this not used anymore? Looks like the same comment still exists in a different/wrong place.

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@grodowski grodowski Nov 7, 2025

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Yup, FileSmallerThan as well as FileNumberDistance were both unused. The latter I used here, too bad I didn't catch the comment before the PR got merge, I'll open another one! #quality

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@grodowski grodowski Nov 7, 2025

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There's more unused stuff there, I'll change the PR base once the build is green. #20

func (this *FileBinlogCoordinates) FileSmallerThan(other BinlogCoordinates) bool {
coord, ok := other.(*FileBinlogCoordinates)
if !ok || other == nil {
return false
}
return this.LogFile < coord.LogFile
}

// FileNumberDistance returns the numeric distance between this coordinate's file number and the other's.
// Effectively it means "how many rotates/FLUSHes would make these coordinates's file reach the other's"
func (this *FileBinlogCoordinates) FileNumberDistance(other *FileBinlogCoordinates) int {
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16 changes: 16 additions & 0 deletions go/mysql/binlog_file_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -134,3 +134,19 @@ func TestIsLogPosOverflowBeyond4Bytes(t *testing.T) {
require.True(t, curCoordinates.IsLogPosOverflowBeyond4Bytes(preCoordinates))
}
}

func TestBinlogCoordinates_LogFileZeroPaddedTransition(t *testing.T) {
c1 := FileBinlogCoordinates{LogFile: "mysql-bin.999999", LogPos: 100}
c2 := FileBinlogCoordinates{LogFile: "mysql-bin.1000000", LogPos: 100}

require.True(t, c1.SmallerThan(&c2))
}

func TestBinlogCoordinates_SameLogFileDifferentPosition(t *testing.T) {
c1 := FileBinlogCoordinates{LogFile: "binlog.000001", LogPos: 100}
c2 := FileBinlogCoordinates{LogFile: "binlog.000001", LogPos: 200}

require.True(t, c1.SmallerThan(&c2))
require.False(t, c2.SmallerThan(&c1))
require.False(t, c1.SmallerThan(&c1))
}
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