Function to_date

pub fn to_date(args: Vec<Expr>) -> Expr

    // define a schema.
    let schema = Arc::new(Schema::new(vec![Field::new("a", DataType::Utf8, false)]));

    // define data.
    let batch = RecordBatch::try_new(
        schema,
        vec![Arc::new(StringArray::from(vec![
            "2020-09-08T13:42:29Z",
            "2020-09-08T13:42:29.190855-05:00",
            "2020-08-09 12:13:29",
            "2020-01-02",
        ]))],
    )?;

    // declare a new context. In spark API, this corresponds to a new spark SQLsession
    let ctx = SessionContext::new();

    // declare a table in memory. In spark API, this corresponds to createDataFrame(...).
    ctx.register_batch("t", batch)?;
    let df = ctx.table("t").await?;

    // use to_date function to convert col 'a' to timestamp type using the default parsing
    let df = df.with_column("a", to_date(vec![col("a")]))?;

    let df = df.select_columns(&["a"])?;

    // print the results
    df.show().await?;