```
ubuntu@ip-172-31-79-147:/opt/downloads$ clickhouse-local --max_threads 8 --query "WITH parseDateTimeBestEffort(extract(_path, 'pageviews-([\\d\\-]+)\\.gz$')) AS time, splitByChar(' ', line) AS values, splitByChar('.', values[1]) AS projects SELECT time, projects[1] AS project, projects[2] AS subproject, values[2] AS path, (values[3])::UInt64 AS hits FROM file('pageviews*.gz', LineAsString) WHERE length(values) >= 3" | pv > /dev/null
^C01GiB 0:01:08 [ 129MiB/s] [                                                                                                                                                                   <=>                                                                                    ]

ubuntu@ip-172-31-79-147:/opt/downloads$ clickhouse-local --max_threads 8 --query "WITH parseDateTimeBestEffort(extract(toLowCardinality(_path), 'pageviews-([\\d\\-]+)\\.gz$')) AS time, splitByChar(' ', line) AS values, splitByChar('.', values[1]) AS projects SELECT time, projects[1] AS project, projects[2] AS subproject, values[2] AS path, (values[3])::UInt64 AS hits FROM file('pageviews*.gz', LineAsString) WHERE length(values) >= 3" | pv > /dev/null
^C46GiB 0:00:48 [ 175MiB/s] [                                                                                                                                                                                                                                        <=>               ]
```

{
        LOG_DEBUG(log,
            "Number of values for sharding key exceeds optimize_skip_unused_shards_limit={}, "
            "try to increase it, but note that this may increase query processing time.",
            local_context->getSettingsRef().optimize_skip_unused_shards_limit);
        return nullptr;
    }
    
    if (!blocks)
    {
        return nullptr;
    }
    std::set<int> shards;
    for (const auto & block : *blocks)
    {
        if (!block.has(sharding_key_column_name))
            throw Exception("sharding_key_expr should evaluate as a single row", ErrorCodes::TOO_MANY_ROWS);
        const ColumnWithTypeAndName & result = block.getByName(sharding_key_column_name);
        const auto selector = createSelector(cluster, result);
        shards.insert(selector.begin(), selector.end());
    }
    return cluster->getClusterWithMultipleShards({shards.begin(), shards.end()});
}
ActionLock StorageDistributed::getActionLock(StorageActionBlockType type)
{
    if (type == ActionLocks::DistributedSend)
        return monitors_blocker.cancel();
    return {};
}
void StorageDistributed::flush()