[GitHub] [arrow] zeroshade commented on a diff in pull request #13806: ARROW-17276: [Go][Integration] Implement IPC handling for union type

[GitBox <gi...@apache.org>]

zeroshade commented on code in PR #13806:
URL: https://github.com/apache/arrow/pull/13806#discussion_r940351554


##########
go/arrow/internal/arrjson/arrjson.go:
##########
@@ -1152,6 +1176,31 @@ func arrayFromJSON(mem memory.Allocator, dt arrow.DataType, arr Array) arrow.Arr
 		defer indices.Release()
 		return array.NewData(dt, indices.Len(), indices.Buffers(), indices.Children(), indices.NullN(), indices.Offset())
 
+	case arrow.UnionType:
+		fields := make([]arrow.ArrayData, len(dt.Fields()))
+		for i, f := range dt.Fields() {
+			child := arrayFromJSON(mem, f.Type, arr.Children[i])
+			defer child.Release()
+			fields[i] = child
+		}
+
+		typeIdBuf := memory.NewBufferBytes(arrow.Int8Traits.CastToBytes(arr.TypeID))
+		defer typeIdBuf.Release()
+		buffers := []*memory.Buffer{nil, typeIdBuf}
+		if dt.Mode() == arrow.DenseMode {
+			var offsets []byte
+			if arr.Offset == nil {
+				offsets = []byte{}

Review Comment:
   It happens in the case of an empty array, which i found when it crashed during archery integration testing lol.



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