neilconway commented on code in PR #23922:
URL: https://github.com/apache/datafusion/pull/23922#discussion_r3666245650
##########
datafusion/functions/src/math/floor.rs:
##########
@@ -234,6 +234,11 @@ impl ScalarUDFImpl for FloorFunc {
Ok(input[0].sort_properties)
}
+ fn strictly_order_preserving(&self, _inputs: &[ExprProperties]) ->
Result<bool> {
+ // floor allow distinct inputs to collapse into equal outputs
Review Comment:
"allows"
##########
datafusion/functions/src/math/factorial.rs:
##########
@@ -116,6 +117,17 @@ impl ScalarUDFImpl for FactorialFunc {
}
}
+ fn output_ordering(&self, inputs: &[ExprProperties]) ->
Result<SortProperties> {
+ // Keep the same ordering as the input
+ Ok(inputs[0].sort_properties)
+ }
+
+ fn strictly_order_preserving(&self, _inputs: &[ExprProperties]) ->
Result<bool> {
+ // There is one-to-one mapping between input and output and nulls maps
to nulls
+ // and because overflow will be resulted in an error and not wrapping
or saturating we are ok
+ Ok(true)
Review Comment:
I don't think this is right: `factorial(0) == factorial(1) == 1`.
##########
datafusion/functions/src/string/repeat.rs:
##########
@@ -160,6 +161,12 @@ impl ScalarUDFImpl for RepeatFunc {
fn documentation(&self) -> Option<&Documentation> {
self.doc()
}
+
+ fn strictly_order_preserving(&self, _inputs: &[ExprProperties]) ->
Result<bool> {
+ // repeat does not strictly preserve ordering since for the following
2 rows:
+ // "bc" and "bca" and repeat(2) the result will be "bcbc" and "bcabca"
which now the order is different
Review Comment:
```suggestion
// repeat('bc', 2) = 'bcbc' > repeat('bca', 2) = 'bcabca', so
ordering is not preserved
```
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