Handle nulls in approx_percentile_cont (#11721)

* Respect nulls in approx_percentile_cont

* Compile

* Remove check

* Adapt comment

Author: Dandandan

datafusion/functions-aggregate/src/approx_percentile_cont.rs

@@ -19,7 +19,8 @@ use std::any::Any;
 use std::fmt::{Debug, Formatter};
 use std::sync::Arc;
 
-use arrow::array::RecordBatch;
+use arrow::array::{Array, RecordBatch};
+use arrow::compute::{filter, is_not_null};
 use arrow::{
     array::{
         ArrayRef, Float32Array, Float64Array, Int16Array, Int32Array, Int64Array,
@@ -393,8 +394,12 @@ impl Accumulator for ApproxPercentileAccumulator {
     }
 
     fn update_batch(&mut self, values: &[ArrayRef]) -> datafusion_common::Result<()> {
-        let values = &values[0];
-        let sorted_values = &arrow::compute::sort(values, None)?;
+        // Remove any nulls before computing the percentile
+        let mut values = Arc::clone(&values[0]);
+        if values.nulls().is_some() {
+            values = filter(&values, &is_not_null(&values)?)?;
+        }
+        let sorted_values = &arrow::compute::sort(&values, None)?;
         let sorted_values = ApproxPercentileAccumulator::convert_to_float(sorted_values)?;
         self.digest = self.digest.merge_sorted_f64(&sorted_values);
         Ok(())

datafusion/sqllogictest/test_files/aggregate.slt

@@ -1237,6 +1237,12 @@ SELECT (ABS(1 - CAST(approx_percentile_cont(c11, 0.9) AS DOUBLE) / 0.834) < 0.05
 ----
 true
 
+# percentile_cont_with_nulls
+query I
+SELECT APPROX_PERCENTILE_CONT(v, 0.5) FROM (VALUES (1), (2), (3), (NULL), (NULL), (NULL)) as t (v);
+----
+2
+
 # csv_query_cube_avg
 query TIR
 SELECT c1, c2, AVG(c3) FROM aggregate_test_100 GROUP BY CUBE (c1, c2) ORDER BY c1, c2