alamb commented on code in PR #8520:
URL: https://github.com/apache/arrow-datafusion/pull/8520#discussion_r1425928916
##########
datafusion/expr/src/expr.rs:
##########
@@ -373,6 +373,24 @@ 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) -> Result<bool> {
+ match self {
+ ScalarFunctionDefinition::BuiltIn(fun) => {
+ Ok(fun.volatility() == crate::Volatility::Volatile)
+ }
+ ScalarFunctionDefinition::UDF(udf) => {
+ Ok(udf.signature().volatility == crate::Volatility::Volatile)
+ }
+ ScalarFunctionDefinition::Name(func) => {
+ internal_err!(
Review Comment:
👍
##########
datafusion/sqllogictest/test_files/functions.slt:
##########
@@ -995,3 +995,9 @@ query ?
SELECT find_in_set(NULL, NULL)
----
NULL
+
+# Verify that multiple calls to volatile functions like `random()` are not
combined / optimized away
+query B
+SELECT r FROM (SELECT r1 == r2 r, r1, r2 FROM (SELECT random() r1, random()
r2) WHERE r1 > 0 AND r2 > 0)
Review Comment:
👍
This test fails on main:
```
❯ SELECT r FROM (SELECT r1 == r2 r, r1, r2 FROM (SELECT random() r1,
random() r2) WHERE r1 > 0 AND r2 > 0)
;
+------+
| r |
+------+
| true |
+------+
1 row in set. Query took 0.037 seconds.
```
##########
datafusion/expr/src/expr.rs:
##########
@@ -373,6 +373,24 @@ 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) -> Result<bool> {
+ match self {
+ ScalarFunctionDefinition::BuiltIn(fun) => {
+ Ok(fun.volatility() == crate::Volatility::Volatile)
+ }
+ ScalarFunctionDefinition::UDF(udf) => {
+ Ok(udf.signature().volatility == crate::Volatility::Volatile)
+ }
+ ScalarFunctionDefinition::Name(func) => {
+ internal_err!(
Review Comment:
👍
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