crepererum commented on code in PR #8520:
URL: https://github.com/apache/arrow-datafusion/pull/8520#discussion_r1425217377
##########
datafusion/expr/src/expr.rs:
##########
@@ -373,6 +373,20 @@ impl ScalarFunctionDefinition {
ScalarFunctionDefinition::Name(func_name) => func_name.as_ref(),
}
}
+
+ /// Whether this function is volatile, i.e. whether it can return
different results
+ /// when evaluated multiple times with the same input.
+ pub fn is_volatile(&self) -> bool {
+ match self {
+ ScalarFunctionDefinition::BuiltIn(fun) => {
+ fun.volatility() == crate::Volatility::Volatile
+ }
+ ScalarFunctionDefinition::UDF(udf) => {
+ udf.signature().volatility == crate::Volatility::Volatile
+ }
+ ScalarFunctionDefinition::Name(_) => false,
Review Comment:
Under which condition does the optimizer see an unresolved function name?
And: if we don't know how the function behaves (because there's only a name)
shouldn't we assume the worst case (i.e. that it is volatile)?
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