Can't cast from Nullable(UInt64)

[Sembl4]

Hello, everyone!
I try to get a value from Nullable(UInt64) column, and I want to get std::optional<uint64_t> as a result, with this code:

block[col]->AsStrict<AsStrict<ColumnNullableT<ColumnUInt64>>()->At(row);

But I have an exception:

terminate called after throwing an instance of 'clickhouse::ValidationError'
what():  Can't cast from Nullable(UInt64)

I can get a value only this way, and this code works good:

if(!block[b_p_b]->AsStrict<ColumnNullable>()->IsNull(row)){
   std::cout << block[b_p_b]->AsStrict<ColumnNullable>()->GetItem(row).get<uint64_t>() << std::endl;
}

But this way is not very good for me, it would be much better if I could get std::optional<uint64_t> as a result of this operation.
Please tell me how can I do this?
Thanks in advance!

[Enmk]

Hi @Sembl4, thank you for a report!

Could you please specify library version and minimal viable example that against which you are able to reproduce the issue?

[Seredenko-V]

@Enmk, hi!

I have the same problem when I try to use the result of executing SELECT. The table stores only one column with the Nullable(Int64) type. An example of the code is attached

#include <clickhouse/client.h>
#include <iostream>

using namespace clickhouse;
using namespace std;

int main()
{
   // ok
   {
      ColumnRef column = std::make_shared< ColumnNullableT< ColumnInt64 > >();
      Block block;
      block.AppendColumn( "nullable_test"s, column );

      auto column2 = block[ 0 ]->As< ::clickhouse::ColumnNullable >();
      block[ 0 ]->AsStrict< ::clickhouse::ColumnNullableT< ::clickhouse::ColumnInt64 > >()->Append( 8 );
      cout << block[ 0 ]->AsStrict< ::clickhouse::ColumnNullableT< ::clickhouse::ColumnInt64 > >()->At( 0 ).value()
           << endl;
   }

   // have proplem
   Client client( ClientOptions().SetHost( "localhost" ) );
   client.Execute( "DROP TABLE IF EXISTS test_data;"s );
   client.Execute( "CREATE TABLE IF NOT EXISTS test_data (nullable_test Nullable(Int64)) ENGINE = Memory;"s );

   Block block;
   ColumnRef column = std::make_shared< ColumnNullableT< ColumnInt64 > >();
   column->AsStrict< ColumnNullableT< ColumnInt64 > >()->Append( 5 );
   block.AppendColumn( "nullable_test"s, column );
   client.Insert( "test_data"s, block );

   clickhouse::Block answer;
   auto handler = [ &answer ]( const Block& block )
   {
      if( block.GetColumnCount() > 0 && block.GetRowCount() > 0 )
         answer = block;
   };

   Query query( "SELECT * FROM test_data;"s );
   query.OnData( handler );
   client.Execute( query );

   //   answer[ 0 ]->AsStrict< ColumnNullableT< ColumnInt64 > >()->Append( 10 );

   // exception "Can't cast from Nullable(Int64)"
   cout << answer[ 0 ]->AsStrict< ColumnNullableT< ColumnInt64 > >()->At( 0 ).has_value() << endl;

   client.Execute( "DROP TABLE IF EXISTS test_data;"s );
   return 0;
}