feat(proto): support Nothing

proto/col_auto.go

@@ -34,6 +34,12 @@ func (c *ColAuto) Infer(t ColumnType) error {
 		return nil
 	}
 	switch t {
+	case ColumnTypeNothing:
+		c.Data = new(ColNothing)
+	case ColumnTypeNullable.Sub(ColumnTypeNothing):
+		c.Data = new(ColNothing).Nullable()
+	case ColumnTypeArray.Sub(ColumnTypeNothing):
+		c.Data = new(ColNothing).Array()
 	case ColumnTypeString:
 		c.Data = new(ColStr)
 	case ColumnTypeArray.Sub(ColumnTypeString):

proto/col_auto_test.go

@@ -40,6 +40,9 @@ func TestColAuto_Infer(t *testing.T) {
 		"IntervalSecond",
 		"IntervalMinute",
 		ColumnType(IntervalHour.String()),
+		ColumnTypeNothing,
+		"Nullable(Nothing)",
+		"Array(Nothing)",
 	} {
 		r := AutoResult("foo")
 		require.NoError(t, r.Data.(Inferable).Infer(columnType))

proto/col_nothing.go

@@ -0,0 +1,57 @@
+package proto
+
+import "fmt"
+
+// Nothing represents NULL value.
+type Nothing struct{}
+
+// ColNothing represents column of null values.
+// Value is row count.
+//
+// https://clickhouse.com/docs/ru/sql-reference/data-types/special-data-types/nothing
+type ColNothing int
+
+func (c *ColNothing) Append(v Nothing) {
+	*c += 1
+}
+
+func (c ColNothing) Row(i int) Nothing {
+	if i >= int(c) {
+		panic(fmt.Sprintf("[%d] of [%d]Nothing", i, c))
+	}
+	return Nothing{}
+}
+
+func (c ColNothing) Type() ColumnType {
+	return ColumnTypeNothing
+}
+
+func (c ColNothing) Rows() int {
+	return int(c)
+}
+
+func (c *ColNothing) DecodeColumn(r *Reader, rows int) error {
+	*c = ColNothing(rows)
+	_, err := r.ReadRaw(rows)
+	return err
+}
+
+func (c *ColNothing) Reset() {
+	*c = 0
+}
+
+func (c *ColNothing) Nullable() *ColNullable[Nothing] {
+	return &ColNullable[Nothing]{
+		Values: c,
+	}
+}
+
+func (c *ColNothing) Array() *ColArr[Nothing] {
+	return &ColArr[Nothing]{
+		Data: c,
+	}
+}
+
+func (c ColNothing) EncodeColumn(b *Buffer) {
+	b.Ensure(int(c))
+}

proto/column.go

@@ -211,6 +211,7 @@ const (
 	ColumnTypeDecimal256     ColumnType = "Decimal256"
 	ColumnTypePoint          ColumnType = "Point"
 	ColumnTypeInterval       ColumnType = "Interval"
+	ColumnTypeNothing        ColumnType = "Nothing"
 )
 
 // colWrap wraps Column with type t.

query_test.go

@@ -855,6 +855,19 @@ func TestClient_Query(t *testing.T) {
 		}), "select table")
 		require.Equal(t, proto.Interval{Scale: proto.IntervalWeek, Value: 1}, data.Row(0))
 	})
+	t.Run("SelectNothing", func(t *testing.T) {
+		t.Parallel()
+		conn := Conn(t)
+
+		data := proto.NewColNullable[proto.Nothing](new(proto.ColNothing))
+		require.NoError(t, conn.Do(ctx, Query{
+			Body: "SELECT NULL as w",
+			Result: proto.Results{
+				{Name: "w", Data: data},
+			},
+		}), "select table")
+		require.False(t, data.Row(0).Set)
+	})
 }
 
 func TestClientCompression(t *testing.T) {