Copilot commented on code in PR #1464:
URL: https://github.com/apache/arrow-go/pull/1464#discussion_r4471929155
##########
arrow/scalar/nested.go:
##########
@@ -352,7 +352,7 @@ type Dictionary struct {
func NewNullDictScalar(dt arrow.DataType) *Dictionary {
ret := &Dictionary{scalar: scalar{dt, false}}
ret.Value.Index = MakeNullScalar(dt.(*arrow.DictionaryType).IndexType)
- ret.Value.Dict = nil
+ ret.Value.Dict = array.MakeArrayOfNull(memory.DefaultAllocator,
dt.(*arrow.DictionaryType).ValueType, 0)
Review Comment:
The new allocation leaks in `compute.NullLiteral`
(`arrow/compute/expression.go:602`): `NewDatum` retains the newly created
dictionary scalar, but releasing the literal leaves its original reference
outstanding. For string dictionaries, this leaves the offsets buffer unreleased
and leaks memory with a mallocator-backed default allocator; the missing-field
paths in `arrow/compute/exprs/exec.go:63,110` have the same issue. Use
`NewDatumWithoutOwning` at these internally created scalar call sites, or
release the original scalar after wrapping it.
##########
arrow/scalar/nested.go:
##########
@@ -352,7 +352,7 @@ type Dictionary struct {
func NewNullDictScalar(dt arrow.DataType) *Dictionary {
ret := &Dictionary{scalar: scalar{dt, false}}
ret.Value.Index = MakeNullScalar(dt.(*arrow.DictionaryType).IndexType)
- ret.Value.Dict = nil
+ ret.Value.Dict = array.MakeArrayOfNull(memory.DefaultAllocator,
dt.(*arrow.DictionaryType).ValueType, 0)
Review Comment:
This now panics for a valid dictionary value type such as
`arrow.StructOf(arrow.Field{Name: "n", Type: arrow.Null})`.
`array.getMaxBufferLen` recursively visits the struct's null field but has no
`NullType` case, so construction panics even at length zero. Add nested-null
support to the array factory, or use an empty-array construction path that
supports this type, and add a regression test.
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