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Write null counts in Parquet statistics when they are known #6490

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merged 6 commits into from
Oct 1, 2024
Merged

Write null counts in Parquet statistics when they are known #6490

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e00e160
Write null counts in parquet files when they are present
alamb Aug 15, 2024
09c4047
Merge remote-tracking branch 'apache/master' into alamb/parquet_null_…
alamb Sep 18, 2024
500f099
Merge remote-tracking branch 'origin/master' into pr/alamb/6257
etseidl Sep 30, 2024
6c05e60
Merge remote-tracking branch 'apache/master' into alamb/parquet_null_…
alamb Oct 1, 2024
51c8424
Merge branch 'alamb/parquet_null_counts' of https://github.com/alamb/…
etseidl Oct 1, 2024
d19a975
continue to treat None as Some(0) on read
etseidl Oct 1, 2024
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103 changes: 96 additions & 7 deletions parquet/src/file/statistics.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -248,20 +248,21 @@ pub fn from_thrift(
pub fn to_thrift(stats: Option<&Statistics>) -> Option<TStatistics> {
let stats = stats?;

// record null counts if greater than zero.
//
// TODO: This should be Some(0) if there are no nulls.
// see https://github.com/apache/arrow-rs/pull/6216/files
// record null count if it can fit in i64
let null_count = stats
.null_count_opt()
.map(|value| value as i64)
.filter(|&x| x > 0);
.and_then(|value| i64::try_from(value).ok());

// record distinct count if it can fit in i64
let distinct_count = stats
.distinct_count_opt()
.and_then(|value| i64::try_from(value).ok());

let mut thrift_stats = TStatistics {
max: None,
min: None,
null_count,
distinct_count: stats.distinct_count_opt().map(|value| value as i64),
distinct_count,
max_value: None,
min_value: None,
is_max_value_exact: None,
Expand Down Expand Up @@ -1052,4 +1053,92 @@ mod tests {
true,
));
}

#[test]
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👏 for thorough test coverage

fn test_count_encoding() {
statistics_count_test(None, None);
statistics_count_test(Some(0), Some(0));
statistics_count_test(Some(100), Some(2000));
statistics_count_test(Some(1), None);
statistics_count_test(None, Some(1));
}

#[test]
fn test_count_encoding_distinct_too_large() {
// statistics are stored using i64, so test trying to store larger values
let statistics = make_bool_stats(Some(u64::MAX), Some(100));
let thrift_stats = to_thrift(Some(&statistics)).unwrap();
assert_eq!(thrift_stats.distinct_count, None); // can't store u64 max --> null
assert_eq!(thrift_stats.null_count, Some(100));
}

#[test]
fn test_count_encoding_null_too_large() {
// statistics are stored using i64, so test trying to store larger values
let statistics = make_bool_stats(Some(100), Some(u64::MAX));
let thrift_stats = to_thrift(Some(&statistics)).unwrap();
assert_eq!(thrift_stats.distinct_count, Some(100));
assert_eq!(thrift_stats.null_count, None); // can' store u64 max --> null
}

#[test]
fn test_count_decoding_null_invalid() {
let tstatistics = TStatistics {
null_count: Some(-42),
..Default::default()
};
let err = from_thrift(Type::BOOLEAN, Some(tstatistics)).unwrap_err();
assert_eq!(
err.to_string(),
"Parquet error: Statistics null count is negative -42"
);
}

/// Writes statistics to thrift and reads them back and ensures:
/// - The statistics are the same
/// - The statistics written to thrift are the same as the original statistics
fn statistics_count_test(distinct_count: Option<u64>, null_count: Option<u64>) {
let statistics = make_bool_stats(distinct_count, null_count);

let thrift_stats = to_thrift(Some(&statistics)).unwrap();
assert_eq!(thrift_stats.null_count.map(|c| c as u64), null_count);
assert_eq!(
thrift_stats.distinct_count.map(|c| c as u64),
distinct_count
);

let round_tripped = from_thrift(Type::BOOLEAN, Some(thrift_stats))
.unwrap()
.unwrap();
// TODO: remove branch when we no longer support assuming null_count==None in the thrift
// means null_count = Some(0)
if null_count.is_none() {
assert_ne!(round_tripped, statistics);
assert!(round_tripped.null_count_opt().is_some());
assert_eq!(round_tripped.null_count_opt(), Some(0));
assert_eq!(round_tripped.min_bytes_opt(), statistics.min_bytes_opt());
assert_eq!(round_tripped.max_bytes_opt(), statistics.max_bytes_opt());
assert_eq!(
round_tripped.distinct_count_opt(),
statistics.distinct_count_opt()
);
} else {
assert_eq!(round_tripped, statistics);
}
}

fn make_bool_stats(distinct_count: Option<u64>, null_count: Option<u64>) -> Statistics {
let min = Some(true);
let max = Some(false);
let is_min_max_deprecated = false;

// test is about the counts, so we aren't really testing the min/max values
Statistics::Boolean(ValueStatistics::new(
min,
max,
distinct_count,
null_count,
is_min_max_deprecated,
))
}
}
52 changes: 26 additions & 26 deletions parquet/tests/arrow_writer_layout.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -189,7 +189,7 @@ fn test_primitive() {
pages: (0..8)
.map(|_| Page {
rows: 250,
page_header_size: 36,
page_header_size: 38,
compressed_size: 1000,
encoding: Encoding::PLAIN,
page_type: PageType::DATA_PAGE,
Expand Down Expand Up @@ -218,22 +218,22 @@ fn test_primitive() {
pages: vec![
Page {
rows: 250,
page_header_size: 36,
page_header_size: 38,
compressed_size: 258,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 1750,
page_header_size: 36,
page_header_size: 38,
compressed_size: 7000,
encoding: Encoding::PLAIN,
page_type: PageType::DATA_PAGE,
},
],
dictionary_page: Some(Page {
rows: 250,
page_header_size: 36,
page_header_size: 38,
compressed_size: 1000,
encoding: Encoding::PLAIN,
page_type: PageType::DICTIONARY_PAGE,
Expand All @@ -260,50 +260,50 @@ fn test_primitive() {
pages: vec![
Page {
rows: 400,
page_header_size: 36,
page_header_size: 38,
compressed_size: 452,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 370,
page_header_size: 36,
page_header_size: 38,
compressed_size: 472,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 330,
page_header_size: 36,
page_header_size: 38,
compressed_size: 464,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 330,
page_header_size: 36,
page_header_size: 38,
compressed_size: 464,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 330,
page_header_size: 36,
page_header_size: 38,
compressed_size: 464,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 240,
page_header_size: 36,
page_header_size: 38,
compressed_size: 332,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
],
dictionary_page: Some(Page {
rows: 2000,
page_header_size: 36,
page_header_size: 38,
compressed_size: 8000,
encoding: Encoding::PLAIN,
page_type: PageType::DICTIONARY_PAGE,
Expand All @@ -329,7 +329,7 @@ fn test_primitive() {
pages: (0..20)
.map(|_| Page {
rows: 100,
page_header_size: 36,
page_header_size: 38,
compressed_size: 400,
encoding: Encoding::PLAIN,
page_type: PageType::DATA_PAGE,
Expand Down Expand Up @@ -364,14 +364,14 @@ fn test_string() {
pages: (0..15)
.map(|_| Page {
rows: 130,
page_header_size: 36,
page_header_size: 38,
compressed_size: 1040,
encoding: Encoding::PLAIN,
page_type: PageType::DATA_PAGE,
})
.chain(std::iter::once(Page {
rows: 50,
page_header_size: 35,
page_header_size: 37,
compressed_size: 400,
encoding: Encoding::PLAIN,
page_type: PageType::DATA_PAGE,
Expand Down Expand Up @@ -400,29 +400,29 @@ fn test_string() {
pages: vec![
Page {
rows: 130,
page_header_size: 36,
page_header_size: 38,
compressed_size: 138,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 1250,
page_header_size: 38,
page_header_size: 40,
compressed_size: 10000,
encoding: Encoding::PLAIN,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 620,
page_header_size: 36,
page_header_size: 38,
compressed_size: 4960,
encoding: Encoding::PLAIN,
page_type: PageType::DATA_PAGE,
},
],
dictionary_page: Some(Page {
rows: 130,
page_header_size: 36,
page_header_size: 38,
compressed_size: 1040,
encoding: Encoding::PLAIN,
page_type: PageType::DICTIONARY_PAGE,
Expand All @@ -449,50 +449,50 @@ fn test_string() {
pages: vec![
Page {
rows: 400,
page_header_size: 36,
page_header_size: 38,
compressed_size: 452,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 370,
page_header_size: 36,
page_header_size: 38,
compressed_size: 472,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 330,
page_header_size: 36,
page_header_size: 38,
compressed_size: 464,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 330,
page_header_size: 36,
page_header_size: 38,
compressed_size: 464,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 330,
page_header_size: 36,
page_header_size: 38,
compressed_size: 464,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
Page {
rows: 240,
page_header_size: 36,
page_header_size: 38,
compressed_size: 332,
encoding: Encoding::RLE_DICTIONARY,
page_type: PageType::DATA_PAGE,
},
],
dictionary_page: Some(Page {
rows: 2000,
page_header_size: 36,
page_header_size: 38,
compressed_size: 16000,
encoding: Encoding::PLAIN,
page_type: PageType::DICTIONARY_PAGE,
Expand Down Expand Up @@ -532,7 +532,7 @@ fn test_list() {
pages: (0..10)
.map(|_| Page {
rows: 20,
page_header_size: 36,
page_header_size: 38,
compressed_size: 672,
encoding: Encoding::PLAIN,
page_type: PageType::DATA_PAGE,
Expand Down
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