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Add ChunkReader::get_bytes #2478

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merged 4 commits into from Aug 17, 2022
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tustvold
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Which issue does this PR close?

Part of #2463

Rationale for this change

This allows for zero-copy slicing when reading from bytes with an offset index.

What changes are included in this PR?

Are there any user-facing changes?

read
));
}
let buffer = self.reader.get_bytes(front.offset as u64, page_len)?;
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@tustvold tustvold Aug 17, 2022

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We can only do this when we have an offset index, as we need to know the size of the page to read. There is a question over whether we could just eagerly fetch the entire column chunk in the latter case, this needs some investigation. It would drastically simplify a lot of the code (it would eliminate FileSource)

Edit: Updated #1163 (comment)

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@Ted-Jiang Ted-Jiang Aug 18, 2022

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Cool ! like we call multi-times skip_rows in one page, this should eagerly fetch the entire column in memory.

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If a page is small enough like 1 mb, i guess there is no defect when using eagerly fetch the entire column. looking forward the investigation result!👍

@github-actions github-actions bot added the parquet Changes to the parquet crate label Aug 17, 2022
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@alamb alamb left a comment

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Makes sense to me

@tustvold tustvold merged commit e80656f into apache:master Aug 17, 2022
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ursabot commented Aug 17, 2022

Benchmark runs are scheduled for baseline = 6d0ea90 and contender = e80656f. e80656f is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java

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4 participants