huaxingao commented on code in PR #564:
URL: https://github.com/apache/datafusion-comet/pull/564#discussion_r1640539424
##########
core/src/execution/datafusion/expressions/covariance.rs:
##########
@@ -287,22 +296,24 @@ impl Accumulator for CovarianceAccumulator {
}
fn evaluate(&mut self) -> Result<ScalarValue> {
+ if self.count == 0.0 {
+ return Ok(ScalarValue::Float64(None));
+ }
Review Comment:
The Spark implementation is:
CovPopulation:
```
if (n == 0.0) {
return null
} else {
return ck/n
}
```
CovSample:
```
if (n == 0.0) {
return null
} else if (n==1.0) {
if (nullOnDivideByZero) {
return null
} else {
return NaN
}
} else {
return ck/(n-1)
}
```
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