IO Utilities#

group IO Utilities

Functions

std::size_t metadata_size_hint()#

Returns the Parquet reader’s footer speculative read size in bytes.

Controlled by the LIBCUDF_PARQUET_METADATA_SIZE_HINT environment variable. Defaults to 64 KiB.

When the footer is smaller than the speculative read size, the footer metadata is loaded in a single read, which is especially useful for high-latency, remote storage systems. When the footer is larger than the speculative read size, the footer metadata will be loaded in two reads.

Set LIBCUDF_PARQUET_METADATA_SIZE_HINT=0 to disable speculative reads.

Returns:

Number of bytes to speculatively read from the end of the source.

std::unique_ptr<cudf::io::datasource::buffer> fetch_footer_to_host(cudf::io::datasource &datasource)#

Fetches a host buffer of Parquet footer bytes from the input data source.

Parameters:

datasource – Input data source

Returns:

Host buffer containing footer bytes

std::vector<std::unique_ptr<cudf::io::datasource::buffer>> fetch_footers_to_host(cudf::host_span<std::reference_wrapper<cudf::io::datasource> const> datasources)#

Fetches host buffers of Parquet footer bytes from multiple input data sources.

Parameters:

datasources – Input data sources

Throws:

cudf::logic_error – if any datasource contains a corrupted Parquet magic number, header or footer, or has an invalid footer length.

Returns:

Vector of host buffers containing footer bytes, one per datasource

std::unique_ptr<cudf::io::datasource::buffer> fetch_page_index_to_host(cudf::io::datasource &datasource, byte_range_info const page_index_bytes)#

Fetches a host buffer of Parquet page index from the input data source.

Parameters:

  • datasource – Input datasource

  • page_index_bytes – Byte range of page index

Returns:

Host buffer containing page index bytes

std::vector<std::unique_ptr<cudf::io::datasource::buffer>> fetch_page_indexes_to_host(cudf::host_span<std::reference_wrapper<cudf::io::datasource> const> datasources, cudf::host_span<byte_range_info const> page_index_bytes_per_source)#

Fetches host buffers of Parquet page index bytes from multiple input data sources.

Parameters:

  • datasources – Input datasources

  • page_index_bytes_per_source – Byte ranges of page index, one per datasource

Throws:

  • cudf::logic_error – if the number of datasources does not match the number of page index byte ranges

  • std::out_of_range – if any page index byte range is out of range for its datasource

Returns:

Vector of host buffers containing page index bytes, one per datasource

std::tuple<std::vector<rmm::device_buffer>, std::vector<cudf::device_span<uint8_t const>>, std::future<void>> fetch_byte_ranges_to_device_async(cudf::io::datasource &datasource, cudf::host_span<byte_range_info const> byte_ranges, rmm::cuda_stream_view stream, rmm::device_async_resource_ref mr)#

Fetches a list of byte ranges from a datasource into device buffers.

Parameters:

  • datasource – Input datasource

  • byte_ranges – Byte ranges to fetch

  • stream – CUDA stream

  • mr – Device memory resource

Returns:

A tuple containing the device buffers, the device spans of the fetched data, and a future to wait on the read tasks

std::tuple<std::vector<rmm::device_buffer>, std::vector<std::vector<cudf::device_span<uint8_t const>>>, std::future<void>> fetch_byte_ranges_to_device_async(cudf::host_span<std::reference_wrapper<cudf::io::datasource> const> datasources, cudf::host_span<std::vector<byte_range_info> const> byte_ranges_per_source, rmm::cuda_stream_view stream, rmm::device_async_resource_ref mr)#

Fetches lists of byte ranges from multiple datasources into device buffers.

Parameters:

  • datasources – Input datasources

  • byte_ranges_per_source – Vector of byte ranges to fetch, one per datasource

  • stream – CUDA stream

  • mr – Device memory resource

Returns:

A tuple containing a vector of device buffers, a vector of vectors of device spans (one per byte range per datasource), and a future to wait on the read tasks