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

Some times there are not output from requests.
virtual_columns_block = getBlockWithVirtualPartColumns(parts, false );
        VirtualColumnUtils::filterBlockWithQuery(query_info.query, virtual_columns_block, local_context, expression_ast);
        part_values = VirtualColumnUtils::extractSingleValueFromBlock<String>(virtual_columns_block, "_part");
        if (part_values.empty())
            return 0;
    }
    
    size_t res = 0;
    for (const auto & part : parts)
    {
        if ((part_values.empty() || part_values.find(part->name) != part_values.end()) && !partition_pruner.canBePruned(*part))
            res += part->rows_count;
    }
    return res;
}
String MergeTreeData::MergingParams::getModeName() const
{
    switch (mode)
    {
        case Ordinary:      return "";
        case Collapsing:    return "Collapsing";
        case Summing:       return "Summing";
        case Aggregating:   return "Aggregating";
        case Replacing:     return "Replacing";
        case Graphite:      return "Graphite";
        case VersionedCollapsing: return "VersionedCollapsing";
    }
    UNREACHABLE();
}
Int64 MergeTreeData::getMaxBlockNumber() const