```
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] [                                                                                                                                                                                                                                        <=>               ]
```

const StorageHDFSPtr & storage,
    const StorageMetadataPtr & metadata_snapshot,
    const ColumnsDescription & columns_description,
    bool need_path_column,
    bool need_file_column)
{
    if (storage->isColumnOriented())
        return metadata_snapshot->getSampleBlockForColumns(
            columns_description.getNamesOfPhysical(), storage->getVirtuals(), storage->getStorageID());
    else
        return getHeader(metadata_snapshot, need_path_column, need_file_column);
}
HDFSSource::DisclosedGlobIterator::DisclosedGlobIterator(ContextPtr context_, const String & uri)
    : pimpl(std::make_shared<HDFSSource::DisclosedGlobIterator::Impl>(context_, uri)) {}
String HDFSSource::DisclosedGlobIterator::next()
{
    return pimpl->next();
}
HDFSSource::URISIterator::URISIterator(const std::vector<const String> & uris_, ContextPtr context)
    : pimpl(std::make_shared<HDFSSource::URISIterator::Impl>(uris_, context))
{
}
String HDFSSource::URISIterator::next()
{
    return pimpl->next();
}
HDFSSource::HDFSSource(