refactor: add more error info when array is empty (#5560)

* refactor: add more error info when array is empty

* make code more concise

* add tests and refine the error report

datafusion/core/tests/sqllogictests/test_files/aggregate.slt

@@ -1284,3 +1284,9 @@ NULL 2
 
 statement ok
 drop table the_nulls;
+
+query error DataFusion error: Execution error: median requires at least one non-null value
+select median(a) from (select 1 as a where 1=0);
+
+query error DataFusion error: Execution error: aggregate function needs at least one non-null element
+select approx_median(a) from (select 1 as a where 1=0);

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

@@ -367,6 +367,11 @@ impl Accumulator for ApproxPercentileAccumulator {
     }
 
     fn evaluate(&self) -> Result<ScalarValue> {
+        if self.digest.count() == 0.0 {
+            return Err(DataFusionError::Execution(
+                "aggregate function needs at least one non-null element".to_string(),
+            ));
+        }
         let q = self.digest.estimate_quantile(self.percentile);
 
         // These acceptable return types MUST match the validation in

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

@@ -143,6 +143,12 @@ impl Accumulator for MedianAccumulator {
     }
 
     fn evaluate(&self) -> Result<ScalarValue> {
+        if !self.all_values.iter().any(|v| !v.is_null()) {
+            return Err(DataFusionError::Execution(
+                "median requires at least one non-null value".into(),
+            ));
+        }
+
         // Create an array of all the non null values and find the
         // sorted indexes
         let array = ScalarValue::iter_to_array(