alamb commented on code in PR #11265:
URL: https://github.com/apache/datafusion/pull/11265#discussion_r1666988190
##########
datafusion/optimizer/src/common_subexpr_eliminate.rs:
##########
@@ -1838,4 +1851,53 @@ mod test {
Ok(())
}
+
+ #[test]
+ fn test_volatile() -> Result<()> {
+ let table_scan = test_table_scan()?;
+
+ let extracted_child = col("a") + col("b");
+ let rand =
Expr::ScalarFunction(ScalarFunction::new_udf(math::random(), vec![]));
+ let not_extracted_volatile = extracted_child + rand;
+ let plan = LogicalPlanBuilder::from(table_scan.clone())
+ .project(vec![
+ not_extracted_volatile.clone().alias("c1"),
+ not_extracted_volatile.alias("c2"),
+ ])?
+ .build()?;
+
+ let expected = "Projection: __common_expr_1 + random() AS c1,
__common_expr_1 + random() AS c2\
+ \n Projection: test.a + test.b AS __common_expr_1, test.a, test.b,
test.c\
+ \n TableScan: test";
+
+ assert_optimized_plan_eq(expected, plan, None);
+
+ Ok(())
+ }
+
+ #[test]
+ fn test_volatile_short_circuits() -> Result<()> {
+ let table_scan = test_table_scan()?;
+
+ let rand =
Expr::ScalarFunction(ScalarFunction::new_udf(math::random(), vec![]));
+ let not_extracted_volatile_short_circuit_2 =
+ rand.clone().eq(lit(0)).or(col("b").eq(lit(0)));
+ let not_extracted_volatile_short_circuit_1 =
+ col("a").eq(lit(0)).or(rand.eq(lit(0)));
+ let plan = LogicalPlanBuilder::from(table_scan.clone())
+ .project(vec![
+ not_extracted_volatile_short_circuit_1.clone().alias("c1"),
+ not_extracted_volatile_short_circuit_1.alias("c2"),
Review Comment:
🤔 I was thinking -- why can't we extract the `a = 0` part of `a = 0 OR
random() = 0` out?
It seems like it would be ok to rewrite
```sql
SELECT
a = 0 OR random() = 0 as c1,
a = 0 OR random() = 0 as c2,
..
```
to something like this:
```sql
SELECT
__subexpr_1 OR random() as c1,
__subexpr_1 OR random() as c2,
...
FROM (
SELECT
a=0 as __subexpr_1
FROM
...
```
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