Replacing pattern matching through downcast with trait method

edmondop · Jul 3, 2024 · 970a7d2 · 970a7d2
1 parent 6993561
commit 970a7d2
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diff --git a/datafusion/physical-expr-common/src/aggregate/mod.rs b/datafusion/physical-expr-common/src/aggregate/mod.rs
@@ -221,6 +221,17 @@ pub trait AggregateExpr: Send + Sync + Debug + PartialEq<dyn Any> {
     ) -> Option<Arc<dyn AggregateExpr>> {
         None
     }
+
+    /// If this function is max, return (output_field, true)
+    /// if the function is min, return (output_field, false)
+    /// otherwise return None (the default)
+    ///
+    /// output_field is the name of the column produced by this aggregate
+    ///
+    /// Note: this is used to use special aggregate implementations in certain conditions
+    fn get_minmax_desc(&self) -> Option<(Field, bool)> {
+        None
+    }
 }
 
 /// Stores the physical expressions used inside the `AggregateExpr`.

diff --git a/datafusion/physical-expr/src/aggregate/min_max.rs b/datafusion/physical-expr/src/aggregate/min_max.rs
@@ -266,6 +266,10 @@ impl AggregateExpr for Max {
     fn create_sliding_accumulator(&self) -> Result<Box<dyn Accumulator>> {
         Ok(Box::new(SlidingMaxAccumulator::try_new(&self.data_type)?))
     }
+
+    fn get_minmax_desc(&self) -> Option<(Field, bool)> {
+        Some((self.field().ok()?, true))
+    }
 }
 
 impl PartialEq<dyn Any> for Max {