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feat(parquet): batch consecutive null/empty rows in write_list #9752

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Merged
alamb merged 1 commit into from
Apr 22, 2026
Merged

feat(parquet): batch consecutive null/empty rows in write_list #9752

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68 changes: 49 additions & 19 deletions parquet/src/arrow/arrow_writer/levels.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -336,51 +336,81 @@ impl LevelInfoBuilder {
})
};

let write_empty_slice = |child: &mut LevelInfoBuilder| {
child.visit_leaves(|leaf| {
let rep_levels = leaf.rep_levels.as_mut().unwrap();
rep_levels.push(ctx.rep_level - 1);
let def_levels = leaf.def_levels.as_mut().unwrap();
def_levels.push(ctx.def_level - 1);
})
let write_null_run = |child: &mut LevelInfoBuilder, count: usize| {

@alamb alamb Apr 22, 2026

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It took me a little while to grok that the empty and null cases got reversed here, but once I got over that it seems good to me

if count > 0 {
child.visit_leaves(|leaf| {
leaf.rep_levels
.as_mut()
.unwrap()
.extend(std::iter::repeat_n(ctx.rep_level - 1, count));
leaf.def_levels
.as_mut()
.unwrap()
.extend(std::iter::repeat_n(ctx.def_level - 2, count));
});
}
};

let write_null_slice = |child: &mut LevelInfoBuilder| {
child.visit_leaves(|leaf| {
let rep_levels = leaf.rep_levels.as_mut().unwrap();
rep_levels.push(ctx.rep_level - 1);
let def_levels = leaf.def_levels.as_mut().unwrap();
def_levels.push(ctx.def_level - 2);
})
let write_empty_run = |child: &mut LevelInfoBuilder, count: usize| {
if count > 0 {
child.visit_leaves(|leaf| {
leaf.rep_levels
.as_mut()
.unwrap()
.extend(std::iter::repeat_n(ctx.rep_level - 1, count));
leaf.def_levels
.as_mut()
.unwrap()
.extend(std::iter::repeat_n(ctx.def_level - 1, count));
});
}
};

match nulls {
Some(nulls) => {
let null_offset = range.start;
let mut pending_nulls: usize = 0;
let mut pending_empties: usize = 0;

// TODO: Faster bitmask iteration (#1757)
for (idx, w) in offsets.windows(2).enumerate() {
let is_valid = nulls.is_valid(idx + null_offset);
let start_idx = w[0].as_usize();
let end_idx = w[1].as_usize();

if !is_valid {
write_null_slice(child)
write_empty_run(child, pending_empties);
pending_empties = 0;
pending_nulls += 1;
} else if start_idx == end_idx {
write_empty_slice(child)
write_null_run(child, pending_nulls);
pending_nulls = 0;
pending_empties += 1;
} else {
write_non_null_slice(child, start_idx, end_idx)
write_null_run(child, pending_nulls);
pending_nulls = 0;
write_empty_run(child, pending_empties);
pending_empties = 0;
write_non_null_slice(child, start_idx, end_idx);
}
}
write_null_run(child, pending_nulls);
write_empty_run(child, pending_empties);
}
None => {
let mut pending_empties: usize = 0;
for w in offsets.windows(2) {
let start_idx = w[0].as_usize();
let end_idx = w[1].as_usize();
if start_idx == end_idx {
write_empty_slice(child)
pending_empties += 1;
} else {
write_non_null_slice(child, start_idx, end_idx)
write_empty_run(child, pending_empties);
pending_empties = 0;
write_non_null_slice(child, start_idx, end_idx);
}
}
write_empty_run(child, pending_empties);
}
}
}
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