[GitHub] [arrow-datafusion] liukun4515 commented on a change in pull request #1387: Add coercion rules for AggregateFunctions

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

liukun4515 commented on a change in pull request #1387:
URL: https://github.com/apache/arrow-datafusion/pull/1387#discussion_r763649897



##########
File path: datafusion/src/physical_plan/aggregates.rs
##########
@@ -87,35 +88,38 @@ impl FromStr for AggregateFunction {
                 return Err(DataFusionError::Plan(format!(
                     "There is no built-in function named {}",
                     name
-                )))
+                )));
             }
         })
     }
 }
 
-/// Returns the datatype of the aggregation function
+/// Returns the datatype of the aggregate function.
+/// This is used to get the returned data type for aggregate expr.
 pub fn return_type(
     fun: &AggregateFunction,
     input_expr_types: &[DataType],
 ) -> Result<DataType> {
     // Note that this function *must* return the same type that the respective physical expression returns
     // or the execution panics.
 
-    // verify that this is a valid set of data types for this function
-    data_types(input_expr_types, &signature(fun))?;
+    let coerced_data_types = coerce_types(fun, input_expr_types, &signature(fun))?;
 
     match fun {
+        // TODO If the datafusion is compatible with PostgreSQL, the returned data type should be INT64.

Review comment:
       https://github.com/apache/arrow-datafusion/issues/1379
   Using the `UINT64` as the result type of `COUNT AGG` is in many places, this will be resolved in https://github.com/apache/arrow-datafusion/issues/1379




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