feat(query): support group by variant

Author: sundy-li

src/query/expression/src/kernels/group_by_hash.rs

@@ -170,6 +170,7 @@ impl HashMethod for HashMethodSingleString {
     fn build_keys_iter<'a>(&self, key_state: &'a KeysState) -> Result<Self::HashKeyIter<'a>> {
         match key_state {
             KeysState::Column(Column::String(col)) => Ok(col.iter()),
+            KeysState::Column(Column::Variant(col)) => Ok(col.iter()),
             _ => unreachable!(),
         }
     }

src/query/service/src/pipelines/processors/transforms/group_by/aggregator_groups_builder.rs

@@ -81,15 +81,16 @@ pub struct SerializedKeysGroupColumnsBuilder<'a> {
 
 impl<'a> SerializedKeysGroupColumnsBuilder<'a> {
     pub fn create(capacity: usize, data_capacity: usize, params: &AggregatorParams) -> Self {
-        let (single_builder, data) =
-            if params.group_data_types.len() == 1 && params.group_data_types[0].is_string() {
-                (
-                    Some(StringColumnBuilder::with_capacity(capacity, data_capacity)),
-                    vec![],
-                )
-            } else {
-                (None, Vec::with_capacity(capacity))
-            };
+        let (single_builder, data) = if params.group_data_types.len() == 1
+            && (params.group_data_types[0].is_string() || params.group_data_types[0].is_variant())
+        {
+            (
+                Some(StringColumnBuilder::with_capacity(capacity, data_capacity)),
+                vec![],
+            )
+        } else {
+            (None, Vec::with_capacity(capacity))
+        };
 
         Self {
             data,
@@ -115,7 +116,11 @@ impl<'a> GroupColumnsBuilder for SerializedKeysGroupColumnsBuilder<'a> {
     fn finish(mut self) -> Result<Vec<Column>> {
         if let Some(builder) = self.single_builder.take() {
             let col = builder.build();
-            return Ok(vec![Column::String(col)]);
+            match self.group_data_types[0] {
+                DataType::String => return Ok(vec![Column::String(col)]),
+                DataType::Variant => return Ok(vec![Column::Variant(col)]),
+                _ => {}
+            }
         }
 
         let rows = self.data.len();

tests/sqllogictests/suites/base/03_common/03_0003_select_group_by

@@ -189,3 +189,20 @@ select (number % 3)::Decimal(19, 2) c, to_string(number % 3) d, count() from num
 0.00 0 34
 1.00 1 33
 2.00 2 33
+
+
+## group by variant  https://github.com/datafuselabs/databend/issues/10603
+
+query TI
+select number::Variant a, count()  from numbers(3) group by a order by a;
+----
+0 1
+1 1
+2 1
+
+query TI
+select number::Variant a, number as b, count()  from numbers(3) group by a, b order by a;
+----
+0 0 1
+1 1 1
+2 2 1