Rebase minio/parquet-go and fix null handling. (#7067)

pkg/s3select/sql/value.go

@@ -58,6 +58,10 @@ func (value *Value) String() string {
 
 // CSVString - encodes to CSV string.
 func (value *Value) CSVString() string {
+	if value.valueType == Null {
+		return ""
+	}
+
 	return fmt.Sprintf("%v", value.value)
 }
 
@@ -66,6 +70,15 @@ func (value *Value) MarshalJSON() ([]byte, error) {
 	return json.Marshal(value.value)
 }
 
+// NullValue - returns underlying null value. It panics if value is not null type.
+func (value *Value) NullValue() *struct{} {
+	if value.valueType == Null {
+		return nil
+	}
+
+	panic(fmt.Sprintf("requested bool value but found %T type", value.value))
+}
+
 // BoolValue - returns underlying bool value. It panics if value is not Bool type.
 func (value *Value) BoolValue() bool {
 	if value.valueType == Bool {