minor: move struct definition out of aggregate/mod.rs, etc (#2458)

Author: WinkerDu

datafusion/core/src/execution/context.rs

@@ -2111,7 +2111,15 @@ mod tests {
             .await
             .unwrap();
 
-        let expected = vec!["+---+", "| a |", "+---+", "| 1 |", "| 2 |", "+---+"];
+        #[rustfmt::skip]
+        let expected = vec![
+            "+---+",
+            "| a |",
+            "+---+",
+            "| 1 |",
+            "| 2 |",
+            "+---+"
+        ];
         assert_batches_eq!(expected, &result);
 
         let result = ctx

datafusion/physical-expr/src/aggregate/count_distinct.rs

@@ -15,7 +15,6 @@
 // specific language governing permissions and limitations
 // under the License.
 
-use super::*;
 use arrow::datatypes::{DataType, Field};
 use std::any::Any;
 use std::fmt::Debug;
@@ -31,6 +30,9 @@ use datafusion_common::ScalarValue;
 use datafusion_common::{DataFusionError, Result};
 use datafusion_expr::Accumulator;
 
+#[derive(Debug, PartialEq, Eq, Hash, Clone)]
+struct DistinctScalarValues(Vec<ScalarValue>);
+
 /// Expression for a COUNT(DISTINCT) aggregation.
 #[derive(Debug)]
 pub struct DistinctCount {

datafusion/physical-expr/src/aggregate/mod.rs

@@ -17,7 +17,7 @@
 
 use crate::PhysicalExpr;
 use arrow::datatypes::Field;
-use datafusion_common::{Result, ScalarValue};
+use datafusion_common::Result;
 use datafusion_expr::Accumulator;
 use std::any::Any;
 use std::fmt::Debug;
@@ -78,6 +78,3 @@ pub trait AggregateExpr: Send + Sync + Debug {
         "AggregateExpr: default name"
     }
 }
-
-#[derive(Debug, PartialEq, Eq, Hash, Clone)]
-struct DistinctScalarValues(Vec<ScalarValue>);