Errors out when writing to external table while using BallistaContext

[saimarpaka]

I have the following piece of code, that i'm trying to run on ballista.

An empty external table called test is created. The goal is to perform computation and insert the result into the test table, as an example.

    let config = BallistaConfig::builder().build()?;

    let ctx = BallistaContext::standalone(&config, 1).await?;

     ctx.sql("
        CREATE EXTERNAL TABLE test (
            c int not null
        )
        STORED AS PARQUET
        LOCATION './examples/testdata2/'
    ").await?.collect().await?;

    ctx.sql("
        CREATE EXTERNAL TABLE aggregate_test_100 ()
        STORED AS PARQUET
        LOCATION './examples/testdata/alltypes_plain.parquet'
    ").await?;

      ctx.sql("insert into test select id from aggregate_test_100").await?
        .collect().await?; 

The above snippet errors out with
Error: DataFusionError(Plan("Column count doesn't match insert query!"))

So I tried to get around this by making the following modifications

   ctx.sql("insert into test select id from aggregate_test_100").await?
        .write_table("test", DataFrameWriteOptions::new()).await?;

still the same Error: DataFusionError(Plan("Column count doesn't match insert query!"))
It appears that empty external tables do not work as expected, when running from Ballista Context. However, they do run, when running from DataFusion context

So I seeded the test table with a parquet from DataFusion context, instead of the Ballista Context to get around this, and performed the following

 let mut df2 =
        ctx.sql("insert into test(c) select id from aggregate_test_100").await?;

    df2.clone()
        .write_table("test", DataFrameWriteOptions::new())
        .await?;

I get the following error
Error: DataFusionError(Internal("failed to serialize logical plan: Internal(\"LogicalPlan serde is not yet implemented for Dml\")"))

Is insertion into External Tables not supported by Ballista at the moment ?
If it is supported, am I doing something wrong here ?