I see what you mean. I was thinking that the function signature would have
to be something like this:
trait Array<T> {
> fn value(&self) -> T
> }
Where T would have to implement another trait, call it ValueTrait, in order
to define how to extract the different values types, e.g. &str, u32, etc.
But as you said, the access to that singular value would be slower
(especially if you want to get multiple values) than downcasting the whole
column to access the values.
I will keep looking at DataFusion to understand how a column is downcasted
automatically based on a RecordBatch schema
Thanks,
On Wed, Jan 27, 2021 at 11:03 PM Andrew Lamb <al...@influxdata.com> wrote:
> I think the idea is enticing, but it comes with some challenges:
>
> 1. Rust is strongly typed so when extracting values we would likely need a
> `Scalar` type enum or multiple different `value_bool`, `value_u64` type
> functions
> 2. Such access would likely be much slower (though possible more
> convenient) as it would dispatch based on type for each row (whereas the
> downcast_as pattern does that dispatch once per array)
>
> Andrew
>
> On Wed, Jan 27, 2021 at 6:27 AM Fernando Herrera <
> fernando.j.herr...@gmail.com> wrote:
>
> > Hi,
> >
> > I'm wondering if it has been considered to move the value function that
> is
> > implemented in all the arrays (StringArray, BooleanArray, ListArray, etc)
> > as part of the Array trait?
> >
> > This would help when extracting values from generic arrays that implement
> > dyn Array without having to manually downcast the array all the time to
> > read a value from the array.
> >
> > Thanks,
> >
>
