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

Some times there are not output from requests.
PartLogElement::Type type,
    const ExecutionStatus & execution_status,
    UInt64 elapsed_ns,
    const String & new_part_name,
    const DataPartPtr & result_part,
    const DataPartsVector & source_parts,
    const MergeListEntry * merge_entry)
try
{
    auto table_id = getStorageID();
    auto part_log = getContext()->getPartLog(table_id.database_name);
    if (!part_log)
        return;
    PartLogElement part_log_elem;
    part_log_elem.event_type = type;
    if (part_log_elem.event_type == PartLogElement::MERGE_PARTS)
    {
        if (merge_entry)
        {
            part_log_elem.merge_reason = PartLogElement::getMergeReasonType((*merge_entry)->merge_type);
            part_log_elem.merge_algorithm = PartLogElement::getMergeAlgorithm((*merge_entry)->merge_algorithm);
        }
    }
    part_log_elem.error = static_cast<UInt16>(execution_status.code);
    part_log_elem.exception = execution_status.message;