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[PARQUET] Improve memory efficency for compressed writer parquet 1.0 #8527

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Merged
alamb merged 3 commits into from
Oct 7, 2025
Merged

[PARQUET] Improve memory efficency for compressed writer parquet 1.0 #8527

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[PARQUET] Improve memory efficency for compressed writer parquet 1.0
lilianm Oct 1, 2025
e79a01e
Merge branch 'main' into parquet_writer_1_0_compressed_memory_improve…
alamb Oct 1, 2025
1b967d9
Merge branch 'main' into parquet_writer_1_0_compressed_memory_improve…
alamb Oct 6, 2025
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1 change: 1 addition & 0 deletions parquet/src/column/writer/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1073,6 +1073,7 @@ impl<'a, E: ColumnValueEncoder> GenericColumnWriter<'a, E> {
if let Some(ref mut cmpr) = self.compressor {
let mut compressed_buf = Vec::with_capacity(uncompressed_size);
cmpr.compress(&buffer[..], &mut compressed_buf)?;
compressed_buf.shrink_to_fit();

@alamb alamb Oct 1, 2025

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I wonder if we should apply the same optimization to V2 path below 🤔

Also, @mapleFU recently updated the compression check for V2 pages to use the uncompressed values if the compression didn't actually reduce the space. Maybe we should apply that to V1 pages too

@lilianm lilianm Oct 2, 2025

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The cost of copy is pretty insignifiant because memcpy speed it's around 10000MB/s and compression speed it's around 600MB/s. Underlayer vector use shink method https://doc.rust-lang.org/alloc/alloc/trait.Allocator.html#method.shrink. In standard malloc threadhold for switch to mmap allocation it's 128k and for shrink the system only unmap page and no need memory copy.

In V2 page buffer is not reserved

For no compress page when compression it's bad i can be a good idea to apply for V1

@lilianm lilianm Oct 2, 2025

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I think it's not possible to disable compression on the fly with page v1
https://github.com/apache/parquet-format/blob/9fd57b59e0ce1a82a69237dcf8977d3e72a2965d/src/main/thrift/parquet.thrift#L671-L692

buffer = compressed_buf;
}

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