liukun4515 commented on a change in pull request #1408:
URL: https://github.com/apache/arrow-datafusion/pull/1408#discussion_r771180890
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File path: datafusion/src/physical_plan/expressions/average.rs
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@@ -102,7 +114,14 @@ impl AggregateExpr for Avg {
}
fn field(&self) -> Result<Field> {
- Ok(Field::new(&self.name, DataType::Float64, true))
+ Ok(Field::new(&self.name, self.data_type.clone(), true))
+ }
+
+ fn create_accumulator(&self) -> Result<Box<dyn Accumulator>> {
+ Ok(Box::new(AvgAccumulator::try_new(
+ // avg is f64 or decimal
+ &self.data_type,
Review comment:
The result type of phy expr(sum/avg) is same with each Accumulator, and
it was decided by `sum_return_type` and `avg_return_type`.
If the column is decimal(8,2), the avg of this column must be less than
`10^10-1`, but we need more digits to represent the decimal part. For example,
The avg of `3,4,6` is `4.333333.....`, we should increase the scale part.
For the sum agg, we just should increase the precision part, and the rule of
adding `10` to precision is spark coercion rule for sum decimal. We can have
our rules for decimal if we want.
@alamb
We can just follow the spark now, and change the rules if we want to define
own rules.
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