matthewgapp commented on code in PR #7638:
URL: https://github.com/apache/arrow-datafusion/pull/7638#discussion_r1335255123
##########
datafusion/expr/src/window_function.rs:
##########
@@ -114,19 +114,35 @@ pub enum BuiltInWindowFunction {
impl BuiltInWindowFunction {
fn name(&self) -> &str {
- use BuiltInWindowFunction::*;
+ use BuiltInWindowFunction as F;
match self {
- RowNumber => "ROW_NUMBER",
- Rank => "RANK",
- DenseRank => "DENSE_RANK",
- PercentRank => "PERCENT_RANK",
- CumeDist => "CUME_DIST",
- Ntile => "NTILE",
- Lag => "LAG",
- Lead => "LEAD",
- FirstValue => "FIRST_VALUE",
- LastValue => "LAST_VALUE",
- NthValue => "NTH_VALUE",
+ F::RowNumber => "ROW_NUMBER",
+ F::Rank => "RANK",
+ F::DenseRank => "DENSE_RANK",
+ F::PercentRank => "PERCENT_RANK",
+ F::CumeDist => "CUME_DIST",
+ F::Ntile => "NTILE",
+ F::Lag => "LAG",
+ F::Lead => "LEAD",
+ F::FirstValue => "FIRST_VALUE",
+ F::LastValue => "LAST_VALUE",
+ F::NthValue => "NTH_VALUE",
+ }
+ }
+
+ // these values need to stay in sync with the `field` value defined on the
physical expressions
+ pub fn nullable(&self) -> bool {
+ use BuiltInWindowFunction as F;
+ match self {
+ F::RowNumber | F::Ntile | F::Rank | F::CumeDist => false,
+ // the rest are assumed to be nullable
Review Comment:
not sure if there is a way that we can derive this from the definitions of
the physical plans or elsewhere? Kinda sucks to have this information hardcoded
this information in two places (right now, it exists also in the `field` method
definition on the `BuildInWindowFunctionExpr` trait
([example](https://github.com/apache/arrow-datafusion/blob/78d9613e81557ca5e5db8b75e5c7dec47ccee0a1/datafusion/physical-expr/src/window/row_number.rs#L54))
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