use MedianGroupsAccumulator.

Author: Rachelint

datafusion/functions-aggregate/src/median.rs

@@ -37,7 +37,8 @@ use arrow::array::Array;
 use arrow::array::ArrowNativeTypeOp;
 use arrow::datatypes::{ArrowNativeType, ArrowPrimitiveType};
 
-use datafusion_common::{DataFusionError, HashSet, Result, ScalarValue};
+use datafusion_common::{internal_err, DataFusionError, HashSet, Result, ScalarValue};
+use datafusion_doc::DocSection;
 use datafusion_expr::function::StateFieldsArgs;
 use datafusion_expr::{
     function::AccumulatorArgs, utils::format_state_name, Accumulator, AggregateUDFImpl,
@@ -172,6 +173,45 @@ impl AggregateUDFImpl for Median {
         }
     }
 
+    fn groups_accumulator_supported(&self, args: AccumulatorArgs) -> bool {
+        !args.is_distinct
+    }
+
+    fn create_groups_accumulator(
+        &self,
+        args: AccumulatorArgs,
+    ) -> Result<Box<dyn GroupsAccumulator>> {
+        let num_args = args.exprs.len();
+        if num_args != 1 {
+            return internal_err!(
+                "median should only have 1 arg, but found num args:{}",
+                args.exprs.len()
+            );
+        }
+
+        let dt = args.exprs[0].data_type(args.schema)?;
+
+        macro_rules! helper {
+            ($t:ty, $dt:expr) => {
+                Ok(Box::new(MedianGroupsAccumulator::<$t>::new($dt)))
+            };
+        }
+
+        downcast_integer! {
+            dt => (helper, dt),
+            DataType::Float16 => helper!(Float16Type, dt),
+            DataType::Float32 => helper!(Float32Type, dt),
+            DataType::Float64 => helper!(Float64Type, dt),
+            DataType::Decimal128(_, _) => helper!(Decimal128Type, dt),
+            DataType::Decimal256(_, _) => helper!(Decimal256Type, dt),
+            _ => Err(DataFusionError::NotImplemented(format!(
+                "MedianGroupsAccumulator not supported for {} with {}",
+                args.name,
+                dt,
+            ))),
+        }
+    }
+
     fn aliases(&self) -> &[String] {
         &[]
     }