GH-48004: [C++][Parquet] Fix hang in ColumnReader benchmark #48005
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The benchmark was instantiating the ColumnReader with less values than it would later attempt to read. The `ReadBatch` method would then return 0 prematurely and the loop would never progress.
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@ursabot please benchmark lang=C++ |
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Benchmark runs are scheduled for commit 2bba103. Watch https://buildkite.com/apache-arrow and https://conbench.ursa.dev for updates. A comment will be posted here when the runs are complete. |
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Component: Parquet
Component: C++
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pitrou
commented
Oct 30, 2025
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| std::shared_ptr<Int64Reader> reader = | ||
| BuildReader(src, state.range(1), codec, schema.get()); | ||
| BuildReader(src, kNumValues, codec, schema.get()); |
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This is the fix: we were instantiating the ColumnReader with the read batch size (state.range(1)) instead of the total number of values (state.range(0)).
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Thanks for your patience. Conbench analyzed the 4 benchmarking runs that have been run so far on PR commit 2bba103. There were 80 benchmark results indicating a performance regression:
The full Conbench report has more details. |
wgtmac
approved these changes
Nov 2, 2025
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206
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| std::shared_ptr<Int64Reader> reader = | ||
| BuildReader(src, state.range(1), codec, schema.get()); | ||
| BuildReader(src, kNumValues, codec, schema.get()); |
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Rationale for this change
The benchmark was instantiating the
ColumnReaderwith less values than it would later attempt to read. TheReadBatchmethod would then return 0 prematurely and the loop would never progress.Are these changes tested?
Manually and by continuous benchmarking.
Are there any user-facing changes?
No.