findepi commented on code in PR #17351:
URL: https://github.com/apache/datafusion/pull/17351#discussion_r2324687435
##########
datafusion/physical-expr-common/src/physical_expr.rs:
##########
@@ -560,3 +573,26 @@ pub fn is_dynamic_physical_expr(expr: &Arc<dyn
PhysicalExpr>) -> bool {
// If the generation is non-zero, then this `PhysicalExpr` is dynamic.
snapshot_generation(expr) != 0
}
+
+/// Returns true if the expression is volatile, i.e. whether it can return
different
+/// results when evaluated multiple times with the same input.
+///
+/// For example the function call `RANDOM()` is volatile as each call will
+/// return a different value.
+///
+/// This method recursively checks if any sub-expression is volatile, for
example
+/// `1 + RANDOM()` will return `true`.
+pub fn is_volatile(expr: &Arc<dyn PhysicalExpr>) -> bool {
+ let mut is_volatile = expr.is_volatile_node();
+ expr.apply(|e| {
+ is_volatile = is_volatile || e.is_volatile_node();
Review Comment:
I thought about sth like
```rust
pub fn is_volatile(expr: &Arc<dyn PhysicalExpr>) -> bool {
if expr.is_volatile_node() {
return true;
}
let mut is_volatile = false;
expr.apply(|e| {
if e.is_volatile_node() {
is_volatile = true;
Ok(TreeNodeRecursion::Stop)
} else {
Ok(TreeNodeRecursion::Continue)
}
})
.expect("infallible closure should not fail");
is_volatile
}
```
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