[GitHub] [arrow-datafusion] alamb commented on a change in pull request #1681: refactor array_agg to not to have `update` and `merge`

[GitBox <gi...@apache.org>]

alamb commented on a change in pull request #1681:
URL: https://github.com/apache/arrow-datafusion/pull/1681#discussion_r792940671



##########
File path: datafusion/src/physical_plan/expressions/array_agg.rs
##########
@@ -95,77 +95,60 @@ impl AggregateExpr for ArrayAgg {
 
 #[derive(Debug)]
 pub(crate) struct ArrayAggAccumulator {
-    array: Vec<ScalarValue>,
+    values: Vec<ScalarValue>,
     datatype: DataType,
 }
 
 impl ArrayAggAccumulator {
     /// new array_agg accumulator based on given item data type
     pub fn try_new(datatype: &DataType) -> Result<Self> {
         Ok(Self {
-            array: vec![],
+            values: vec![],
             datatype: datatype.clone(),
         })
     }
-
-    fn update(&mut self, values: &[ScalarValue]) -> Result<()> {
-        let value = &values[0];
-        self.array.push(value.clone());
-
-        Ok(())
-    }
-
-    fn merge(&mut self, states: &[ScalarValue]) -> Result<()> {
-        if states.is_empty() {
-            return Ok(());
-        };
-
-        assert!(states.len() == 1, "states length should be 1!");
-        match &states[0] {
-            ScalarValue::List(Some(array), _) => {
-                self.array.extend((&**array).clone());
-            }
-            _ => unreachable!(),
-        }
-        Ok(())
-    }
 }
 
 impl Accumulator for ArrayAggAccumulator {
     fn update_batch(&mut self, values: &[ArrayRef]) -> Result<()> {
         if values.is_empty() {
             return Ok(());
         };
-        (0..values[0].len()).try_for_each(|index| {
-            let v = values
-                .iter()
-                .map(|array| ScalarValue::try_from_array(array, index))
-                .collect::<Result<Vec<_>>>()?;
-            self.update(&v)
+        assert!(values.len() == 1, "array_agg can only take 1 param!");

Review comment:
       I like the new assert 👍 




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