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fix(arrow/array): Resize(0) on non-empty builder causes memory leak #995

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Merged
zeroshade merged 2 commits into from
Jul 24, 2026
Merged

fix(arrow/array): Resize(0) on non-empty builder causes memory leak #995

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b868d27
Add unit test repro to `Append` then `Resize` memory leak
serramatutu Jul 24, 2026
43112fa
Make `resize` use `minBuilderCapacity`
serramatutu Jul 24, 2026
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5 changes: 3 additions & 2 deletions arrow/array/builder.go
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Original file line number Diff line number Diff line change
Expand Up @@ -164,10 +164,11 @@ func (b *builder) resize(newBits int, init func(int)) {
return
}

newBytesN := bitutil.CeilByte(newBits) / 8
allocBits := max(newBits, minBuilderCapacity)
newBytesN := bitutil.CeilByte(allocBits) / 8
oldBytesN := b.nullBitmap.Len()
b.nullBitmap.Resize(newBytesN)
b.capacity = newBits
b.capacity = allocBits
if oldBytesN < newBytesN {
// TODO(sgc): necessary?
memory.Set(b.nullBitmap.Buf()[oldBytesN:], 0)
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183 changes: 183 additions & 0 deletions arrow/array/numericbuilder.gen_test.go
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17 changes: 17 additions & 0 deletions arrow/array/numericbuilder.gen_test.go.tmpl
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Original file line number Diff line number Diff line change
Expand Up @@ -272,6 +272,23 @@ func Test{{.Name}}Builder_Resize(t *testing.T) {
assert.Equal(t, 5, ab.Len())
}

func Test{{.Name}}Builder_ResizeToZeroThenAppend(t *testing.T) {
mem := memory.NewCheckedAllocator(memory.NewGoAllocator())
defer mem.AssertSize(t, 0)

{{if .Opt.Parametric -}}
dtype := &arrow.{{.Name}}Type{Unit: arrow.Second}
ab := array.New{{.Name}}Builder(mem, dtype)
{{else}}
ab := array.New{{.Name}}Builder(mem)
{{end -}}
defer ab.Release()

ab.Append(0)
ab.Resize(0)
ab.Append(0)
}

func Test{{.Name}}BuilderUnmarshalJSON(t *testing.T) {
mem := memory.NewCheckedAllocator(memory.NewGoAllocator())
defer mem.AssertSize(t, 0)
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