Add creator from Iterator of i128 to get the decimalarray

[liukun4515]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
From this comments in the datafusion.
apache/datafusion#1394 (comment)

apache/datafusion#1394

Creating an DecimalArray from an array of Option<i128> using DecimalBuilder is quite painful (see apache/datafusion#1394)

Ideally it would be possible to do something similar to the PrimitiveArrays, such as https://docs.rs/arrow/6.3.0/arrow/array/type.UInt32Array.html#example-using-collect

// get an iterator over `Option<i128>`
let data: Vec<Option<i128>> = ....;
let array: DecimalArray = data.into_iter().collect();

Describe the solution you'd like
However, since DecimalArray has precision and scale in its DataType, we need some way to specify that.

One thought, would be a function such as (for precision 20 and scale 5):

let array = DecimalArray::from_iter_and_scale(20, 5, data.iter())

An alternate might be something more like:

// creates a decimal array with default precision 32 and scale 0 (could be something else)
let array: DecimalArray = data.into_iter().collect();
// consume the existing array and make a new one with a different declared precision and scale
let array = array.with_precision_and_scale(20, 5);

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[liukun4515]

Please assign this to me.

[alamb]

Hi @liukun4515 -- thanks for the ticket; I added some more description to this ticket and some ideas which hopefully would help.

[liukun4515]

Hi @liukun4515 -- thanks for the ticket; I added some more description to this ticket and some ideas which hopefully would help.

Thank you.
I think the decimal type is more complex than other types, I will start this task when the tasks in the datafusion ends.

[alamb]

BTW the more I tried playing around with this, the nicer I think it would be to be able to do something like

    let array : DecimalArray = vec![1,2,3].into()
        .with_precision(10)
        .with_scale(5);

[liukun4515]

BTW the more I tried playing around with this, the nicer I think it would be to be able to do something like

Yes, we can follow the usage of other primitive arrays to implement the necessary function first.

[alamb]

i took a crack at this in #1223