more plumbing

Author: alamb

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

@@ -29,7 +29,7 @@ use crate::aggregate::sum::sum_batch;
 use crate::aggregate::utils::calculate_result_decimal_for_avg;
 use crate::aggregate::utils::down_cast_any_ref;
 use crate::expressions::format_state_name;
-use crate::{AggregateExpr, PhysicalExpr};
+use crate::{AggregateExpr, GroupsAccumulator, PhysicalExpr};
 use arrow::compute;
 use arrow::datatypes::DataType;
 use arrow::{
@@ -155,6 +155,13 @@ impl AggregateExpr for Avg {
             &self.rt_data_type,
         )?))
     }
+
+    fn create_groups_accumulator(&self) -> Result<Box<dyn GroupsAccumulator>> {
+        Ok(Box::new(AvgGroupsAccumulator::new(
+            &self.sum_data_type,
+            &self.rt_data_type,
+        )))
+    }
 }
 
 impl PartialEq<dyn Any> for Avg {
@@ -383,6 +390,55 @@ impl RowAccumulator for AvgRowAccumulator {
     }
 }
 
+/// An accumulator to compute the average
+#[derive(Debug)]
+pub struct AvgGroupsAccumulator {
+    sum_data_type: DataType,
+    return_data_type: DataType,
+    //count: u64,
+}
+
+impl AvgGroupsAccumulator {
+    pub fn new(sum_datatype: &DataType, return_data_type: &DataType) -> Self {
+        Self {
+            sum_data_type: sum_datatype.clone(),
+            return_data_type: return_data_type.clone(),
+        }
+    }
+}
+
+impl GroupsAccumulator for AvgGroupsAccumulator {
+    fn update_batch(
+        &mut self,
+        values: &[ArrayRef],
+        group_indicies: &[usize],
+        opt_filter: Option<&arrow_array::BooleanArray>,
+    ) -> Result<usize> {
+        todo!()
+    }
+
+    fn evaluate(&mut self) -> Result<ArrayRef> {
+        todo!()
+    }
+
+    fn state(&mut self) -> Result<Vec<ArrayRef>> {
+        todo!()
+    }
+
+    fn merge_batch(
+        &mut self,
+        values: &[ArrayRef],
+        group_indicies: &[usize],
+        opt_filter: Option<&arrow_array::BooleanArray>,
+    ) -> Result<()> {
+        todo!()
+    }
+
+    fn size(&self) -> usize {
+        todo!()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;