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fix(ipc): preserve map child field metadata #809

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Merged
zeroshade merged 1 commit into from
May 12, 2026
+42 −2
Merged

fix(ipc): preserve map child field metadata #809

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3 changes: 1 addition & 2 deletions arrow/ipc/metadata.go
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Original file line number Diff line number Diff line change
Expand Up @@ -843,8 +843,7 @@ func concreteTypeFromFB(typ flatbuf.Type, data flatbuffers.Table, children []arr

var dt flatbuf.Map
dt.Init(data.Bytes, data.Pos)
ret := arrow.MapOf(pairType.Field(0).Type, pairType.Field(1).Type)
ret.SetItemNullable(pairType.Field(1).Nullable)
ret := arrow.MapOfFields(pairType.Field(0), pairType.Field(1))
ret.KeysSorted = dt.KeysSorted()
return ret, nil

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41 changes: 41 additions & 0 deletions arrow/ipc/metadata_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,47 @@ func TestRWSchema(t *testing.T) {
}
}

func TestMapFieldMetadataRoundTrip(t *testing.T) {
keyMeta := arrow.NewMetadata([]string{"my.key.id"}, []string{"100"})
itemMeta := arrow.NewMetadata([]string{"my.item.id"}, []string{"200"})

mapType := arrow.MapOfFields(
arrow.Field{Name: "key", Type: arrow.BinaryTypes.String, Metadata: keyMeta},
arrow.Field{Name: "value", Type: arrow.PrimitiveTypes.Int32, Nullable: true, Metadata: itemMeta},
)
mapType.KeysSorted = true
schema := arrow.NewSchema([]arrow.Field{
{Name: "m", Type: mapType, Nullable: true},
}, nil)

var buf bytes.Buffer
w := NewWriter(&buf, WithSchema(schema), WithAllocator(memory.DefaultAllocator))
if err := w.Close(); err != nil {
t.Fatal(err)
}

r, err := NewReader(bytes.NewReader(buf.Bytes()), WithAllocator(memory.DefaultAllocator))
if err != nil {
t.Fatal(err)
}
defer r.Release()

roundTripped := r.Schema()
if !roundTripped.Equal(schema) {
t.Fatalf("schema mismatch after IPC round-trip:\ngot: %s\nwant: %s", roundTripped, schema)
}

rtMap := roundTripped.Field(0).Type.(*arrow.MapType)
if got, ok := rtMap.KeyField().Metadata.GetValue("my.key.id"); !ok || got != "100" {
t.Fatalf("key field metadata lost after IPC round-trip: got keys=%v", rtMap.KeyField().Metadata.Keys())
}
if got, ok := rtMap.ItemField().Metadata.GetValue("my.item.id"); !ok || got != "200" {
t.Fatalf("item field metadata lost after IPC round-trip: got keys=%v", rtMap.ItemField().Metadata.Keys())
}
assert.True(t, rtMap.ItemField().Nullable)
assert.True(t, rtMap.KeysSorted)
}

func TestRWFooter(t *testing.T) {
for _, tc := range []struct {
schema *arrow.Schema
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