liukun4515 commented on a change in pull request #1394:
URL: https://github.com/apache/arrow-datafusion/pull/1394#discussion_r762500418
##########
File path: datafusion/src/scalar.rs
##########
@@ -831,13 +892,40 @@ impl ScalarValue {
"Unsupported creation of {:?} array from ScalarValue {:?}",
data_type,
scalars.peek()
- )))
+ )));
}
};
Ok(array)
}
+ fn iter_to_decimal_array(
+ scalars: impl IntoIterator<Item = ScalarValue>,
+ precision: &usize,
+ scale: &usize,
+ ) -> Result<DecimalArray> {
+ // collect the value as Option<i128>
+ let array = scalars
+ .into_iter()
+ .map(|element: ScalarValue| match element {
+ ScalarValue::Decimal128(v1, _, _) => v1,
+ _ => unreachable!(),
+ })
+ .collect::<Vec<Option<i128>>>();
Review comment:
>
Yes, we can add the `from_iter_and_scale` function in arrow-rs later and
replace this in the followup pull request.
Do you agree this? @alamb
##########
File path: datafusion/src/scalar.rs
##########
@@ -453,6 +477,26 @@ macro_rules! eq_array_primitive {
}
impl ScalarValue {
+ /// Create a decimal Scalar from value/precision and scale.
+ pub fn try_new_decimal128(
+ value: i128,
+ precision: usize,
+ scale: usize,
+ ) -> Result<Self> {
+ // make sure the precision and scale is valid
+ // TODO const the max precision and min scale
Review comment:
If we use 128bit to represent a decimal value, the max `precision` is 38.
The `scale` is always greater or equal to 0 and less than or equal to
`precision`.
In the arrow-rs, the decimal is represented by `i128` with `precision` and
`scale`.
So we can add the `MAX_PRECISION = 38` in the datafusion.
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