Support NULL literal in Min/Max (#11812)

* Support NULL literal in Min/Max * Fix ut * fix fmt --------- Co-authored-by: Andrew Lamb <[email protected]>
apache · Aug 8, 2024 · 56be714 · 56be714
1 parent 1c9583a
commit 56be714
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Showing 4 changed files with 14 additions and 3 deletions.
diff --git a/datafusion/core/src/dataframe/mod.rs b/datafusion/core/src/dataframe/mod.rs
@@ -717,7 +717,10 @@ impl DataFrame {
                             {
                                 let column =
                                     batchs[0].column_by_name(field.name()).unwrap();
-                                if field.data_type().is_numeric() {
+
+                                if column.data_type().is_null() {
+                                    Arc::new(StringArray::from(vec!["null"]))
+                                } else if field.data_type().is_numeric() {
                                     cast(column, &DataType::Float64)?
                                 } else {
                                     cast(column, &DataType::Utf8)?

diff --git a/datafusion/core/tests/dataframe/describe.rs b/datafusion/core/tests/dataframe/describe.rs
@@ -102,8 +102,8 @@ async fn describe_null() -> Result<()> {
         "| null_count | 0    | 1    |",
         "| mean       | null | null |",
         "| std        | null | null |",
-        "| min        | null | null |",
-        "| max        | null | null |",
+        "| min        | a    | null |",
+        "| max        | a    | null |",
         "| median     | null | null |",
         "+------------+------+------+"
     ];

diff --git a/datafusion/functions-aggregate/src/min_max.rs b/datafusion/functions-aggregate/src/min_max.rs
@@ -304,6 +304,7 @@ macro_rules! typed_min_max_batch {
 macro_rules! min_max_batch {
     ($VALUES:expr, $OP:ident) => {{
         match $VALUES.data_type() {
+            DataType::Null => ScalarValue::Null,
             DataType::Decimal128(precision, scale) => {
                 typed_min_max_batch!(
                     $VALUES,
@@ -579,6 +580,7 @@ macro_rules! interval_min_max {
 macro_rules! min_max {
     ($VALUE:expr, $DELTA:expr, $OP:ident) => {{
         Ok(match ($VALUE, $DELTA) {
+            (ScalarValue::Null, ScalarValue::Null) => ScalarValue::Null,
             (
                 lhs @ ScalarValue::Decimal128(lhsv, lhsp, lhss),
                 rhs @ ScalarValue::Decimal128(rhsv, rhsp, rhss)

diff --git a/datafusion/sqllogictest/test_files/aggregate.slt b/datafusion/sqllogictest/test_files/aggregate.slt
@@ -5548,3 +5548,9 @@ set datafusion.explain.logical_plan_only = false;
 
 statement ok
 drop table employee_csv;
+
+# test null literal handling in supported aggregate functions
+query I??III?T
+select count(null), min(null), max(null), bit_and(NULL), bit_or(NULL), bit_xor(NULL), nth_value(NULL, 1), string_agg(NULL, ',');
+----
+0 NULL NULL NULL NULL NULL NULL NULL