GH-44769: [C++][Parquet] Fix read/write of metadata length footer on big-endian systems #44787
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By converting the `uint32_t` to little endian before casting to a `uint8_t*`, this is always correct in the output file.
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Component: Parquet
Component: C++
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mapleFU
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Nov 19, 2024
cpp/src/parquet/file_writer.cc
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| metadata_len = ::arrow::bit_util::ToLittleEndian(metadata_len); | ||
| PARQUET_THROW_NOT_OK(sink->Write(reinterpret_cast<uint8_t*>(&metadata_len), 4)); |
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| metadata_len = ::arrow::bit_util::ToLittleEndian(metadata_len); | |
| PARQUET_THROW_NOT_OK(sink->Write(reinterpret_cast<uint8_t*>(&metadata_len), 4)); | |
| { | |
| uint32_t metadata_len_le = ::arrow::bit_util::ToLittleEndian(metadata_len); | |
| PARQUET_THROW_NOT_OK(sink->Write(reinterpret_cast<uint8_t*>(&metadata_len_le), 4)); | |
| } |
Can we solve like this?
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pitrou
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Nov 19, 2024
cpp/src/parquet/file_writer.cc
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| PARQUET_ASSIGN_OR_THROW(position, sink->Tell()); | ||
| metadata_len = static_cast<uint32_t>(position) - metadata_len; | ||
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| metadata_len = ::arrow::bit_util::ToLittleEndian(metadata_len); |
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Rerun ci, would merge if it passes |
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Thanks all, merged! |
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After merging your PR, Conbench analyzed the 3 benchmarking runs that have been run so far on merge-commit 9015a81. There were no benchmark performance regressions. 🎉 The full Conbench report has more details. |
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Rationale for this change
See issue.
What changes are included in this PR?
Fix writing Parquet metadata length footer
By converting the
uint32_tto little endian before casting to auint8_t*, this is always correct in the output file.Fix reading Parquet metadata length footer
Are these changes tested?
Yes.
Are there any user-facing changes?
Reading a Parquet file won't complain about metadata size in the footer, though that doesn't guarantee anything else will work yet.