findepi commented on code in PR #11256:
URL: https://github.com/apache/datafusion/pull/11256#discussion_r1666020300
##########
datafusion/expr/src/expr_schema.rs:
##########
@@ -322,10 +322,16 @@ impl ExprSchemable for Expr {
}
}
Expr::Cast(Cast { expr, .. }) => expr.nullable(input_schema),
- Expr::AggregateFunction(AggregateFunction { func_def, .. }) => {
+ Expr::AggregateFunction(AggregateFunction { func_def, args, .. })
=> {
match func_def {
+ // TODO: min/max over non-nullable input should be
recognized as non-nullable
AggregateFunctionDefinition::BuiltIn(fun) =>
fun.nullable(),
// TODO: UDF should be able to customize nullability
Review Comment:
To address this TODO we could extend the pattern here
https://github.com/apache/datafusion/blob/4bc322819f28695b6b9593d5bbaea775e7d798b6/datafusion/expr/src/aggregate_function.rs#L84-L88
ie now we have `return_type(input_types, nullability) -> return_type`
we could have `return_type(input_types, nullability) -> (return_type,
nullability)`
this is an API for builtin functions, we would need similar API for UDAFs
https://github.com/apache/datafusion/blob/5f02c8a0658d9ed012ca4ca91f0417a967fe094a/datafusion/expr/src/udaf.rs#L330
Obviously, this would be a breaking change: both method signature and return
type would change.
We can avoid the breaking change by making nullability a separate method,
but it would be good to first determine the ideal end-state, and only then
think how to get there.
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