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

StorageHDFSPtr storage_,
    const StorageMetadataPtr & metadata_snapshot_,
    ContextPtr context_,
    UInt64 max_block_size_,
    bool need_path_column_,
    bool need_file_column_,
    std::shared_ptr<IteratorWrapper> file_iterator_,
    ColumnsDescription columns_description_)
    : SourceWithProgress(getBlockForSource(storage_, metadata_snapshot_, columns_description_, need_path_column_, need_file_column_))
    , WithContext(context_)
    , storage(std::move(storage_))
    , metadata_snapshot(metadata_snapshot_)
    , max_block_size(max_block_size_)
    , need_path_column(need_path_column_)
    , need_file_column(need_file_column_)
    , file_iterator(file_iterator_)
    , columns_description(std::move(columns_description_))
{
    initialize();
}
void HDFSSource::onCancel()
{
    std::lock_guard lock(reader_mutex);
    if (reader)
        reader->cancel();
}
bool HDFSSource::initialize()