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Parquet: Do not compress v2 data page when compress is bad quality #8257

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Merged
merged 3 commits into from
Sep 8, 2025
Merged

Parquet: Do not compress v2 data page when compress is bad quality #8257

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e0077f9
Do not compress v2 data page when compress is bad quality
mapleFU Sep 1, 2025
2d66332
Merge branch 'main' into page-v2-no-compress-if-size-too-lage
mapleFU Sep 5, 2025
0e198e9
Add testing
mapleFU Sep 5, 2025
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19 changes: 15 additions & 4 deletions parquet/src/column/writer/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1104,12 +1104,23 @@ impl<'a, E: ColumnValueEncoder> GenericColumnWriter<'a, E> {
rep_levels_byte_len + def_levels_byte_len + values_data.buf.len();

// Data Page v2 compresses values only.
match self.compressor {
let is_compressed = match self.compressor {
Some(ref mut cmpr) => {
let buffer_len = buffer.len();
cmpr.compress(&values_data.buf, &mut buffer)?;
if uncompressed_size <= buffer.len() - buffer_len {
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This can also be a "score", like if uncompressed_size <= (buffer.len() - buffer_len) * 0.9 {

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I'd suggest maybe going the opposite direction. If compression doesn't give say a 10% size reduction, then don't compress...it will be faster to read. 10% might be too much...maybe we could make it configurable.

Anyway, that's probably out of scope for this PR. Let's just go with the simple test for now...it's still an improvement.

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Yeah, I do think that would need to configurable as I think some people would treat a 10% size increase as a regression, even if they got a faster reader

A good follow on ticket for sure

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I’ll follow up once there’s a plan for this future ticket. Just a note from me —the score is still a highly empirical value (and depends on the decompression speed), so I’ve embedded it into my rewriter and have been extensively rewriting Parquet files based on it.

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In my opinion, given there is a tradeoff here (file size / decode speed) we can't hard code some heuristic that changes the default behavior.

However, I think it would be a good improvement to add some sort of tuning knob for people who wanted to make that tradeoff more explicitly as long as the default setting of the knob leaves the existing behavior

buffer.truncate(buffer_len);
buffer.extend_from_slice(&values_data.buf);
false
} else {
true
}
}
None => buffer.extend_from_slice(&values_data.buf),
}
None => {
buffer.extend_from_slice(&values_data.buf);
false
}
};

let data_page = Page::DataPageV2 {
buf: buffer.into(),
Expand All @@ -1119,7 +1130,7 @@ impl<'a, E: ColumnValueEncoder> GenericColumnWriter<'a, E> {
num_rows: self.page_metrics.num_buffered_rows,
def_levels_byte_len: def_levels_byte_len as u32,
rep_levels_byte_len: rep_levels_byte_len as u32,
is_compressed: self.compressor.is_some(),
is_compressed,
statistics: page_statistics,
};

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