Statistics
https://play.clickhouse.com/play?user=play#c2VsZWN0IAp0b1N0YXJ0T2ZIb3VyKGNoZWNrX3N0YXJ0X3RpbWUpIGFzIGQsCmNvdW50KCksICBncm91cFVuaXFBcnJheShwdWxsX3JlcXVlc3RfbnVtYmVyKSwgIGFueShyZXBvcnRfdXJsKQpmcm9tIGNoZWNrcyB3aGVyZSAnMjAyMi0wNi0wMScgPD0gY2hlY2tfc3RhcnRfdGltZSBhbmQgdGVzdF9uYW1lIGxpa2UgJyUwMjQ5MV9wYXJ0X2xvZ19oYXNfdGFibGVfdXVpZCUnIGFuZCB0ZXN0X3N0YXR1cyBpbiAoJ0ZBSUwnLCAnRkxBS1knKSBncm91cCBieSBkIG9yZGVyIGJ5IGQgZGVzYw==

Some times there are not output from requests.
{
        if (analysis_result.before_where)
        {
            candidate.where_column_name = analysis_result.where_column_name;
            candidate.remove_where_filter = !required_columns.contains(analysis_result.where_column_name);
            candidate.before_where = analysis_result.before_where->clone();
            auto new_required_columns = candidate.before_where->foldActionsByProjection(
                required_columns,
                projection.sample_block_for_keys,
                candidate.where_column_name);
            if (new_required_columns.empty() && !required_columns.empty())
                return false;
            required_columns = std::move(new_required_columns);
            candidate.before_where->addAggregatesViaProjection(aggregates);
        }
        if (analysis_result.prewhere_info)
        {
            candidate.prewhere_info = analysis_result.prewhere_info->clone();
            auto prewhere_actions = candidate.prewhere_info->prewhere_actions->clone();
            auto prewhere_required_columns = required_columns;
            
            for (const auto & column : prewhere_actions->getResultColumns())
                required_columns.erase(column.name);
            {
                
                auto new_prewhere_required_columns = prewhere_actions->foldActionsByProjection(
                        prewhere_required_columns, projection.sample_block_for_keys, candidate.prewhere_info->prewhere_column_name, false);
                if (new_prewhere_required_columns.empty() && !prewhere_required_columns.empty())
                    return false;
                prewhere_required_columns = std::move(new_prewhere_required_columns);