Schema::empty()
<https://github.com/apache/arrow/blob/8e43f23dcc6a9e630516228f110c48b64d13cec6/rust/arrow/src/datatypes/schema.rs#L43>
serializes to "{\"fields\":[]}". Metadata is not present because of
skip_serializing_if. This is the error that would be given if the above
string is deserialized: Error("missing field `metadata`", line: 1, column:
13).
Jack
Andrew Lamb <al...@influxdata.com> 於 2021年4月5日週一 上午3:36寫道：
> Did the metadata successfully serialize with serde json (this is a little
> unclear to me given your description).
>
> > I would expect that every schema can be serialized-deserialized back in
> itself.
>
> I have the same expectation.
>
> If metadata can't be serialized with serde_json that would seem like a bug
> to me and I think the project would appreciate help fixing it.
>
> Thanks,
> Andrew
>
> On Sun, Apr 4, 2021 at 10:40 AM Jack Chan <j4ck....@gmail.com> wrote:
>
> > Indeed, I did, with both serde json and dynamodb. Inside an arrow schema,
> > the metadata field is a hashmap with skip serializing if empty. When
> > deserializing, it expects a metadata field. I would expect that every
> > schema can be serialized-deserialized back in itself.
> >
> > Jack
> >
> > On Sat, Apr 3, 2021, 10:59 AM Andrew Lamb <al...@influxdata.com> wrote:
> >
> > > This looks like a rust program. Perhaps you could try using
> `serde_json`
> > or
> > > some other format to narrow down where the issue is
> > >
> > > On Fri, Apr 2, 2021 at 10:00 PM Jack Chan <j4ck....@gmail.com> wrote:
> > >
> > > > Hi
> > > >
> > > > I tried to serialize and deserialize an arrow schema, but I got into
> an
> > > > error of
> > > > (Error { message: "missing field `metadata`" }). Is this a bug in
> > apache
> > > > arrow or in serde_dynamodb?
> > > >
> > > > ```
> > > > let schema = ArrowSchema::empty();
> > > > let object = serde_dynamodb::to_hashmap(&schema)?;
> > > > let roundtrip: ArrowSchema =
> > > serde_dynamodb::from_hashmap(object)?;
> > > > assert_eq!(roundtrip, schema);
> > > > ```
> > > >
> > > > Jack
> > > >
> > >
> >
>
