neilconway opened a new issue, #10860:
URL: https://github.com/apache/arrow-rs/issues/10860
### Describe the bug
When a BYTE_ARRAY DECIMAL column contains values whose encodings have
different byte lengths, the written row-group/page statistics can be wrong; see
repro for example (min/max swapped).
### To Reproduce
```rust
use parquet::basic::{ConvertedType, Repetition, Type as PhysicalType};
use parquet::data_type::{ByteArray, ByteArrayType};
use parquet::file::properties::WriterProperties;
use parquet::file::reader::FileReader;
use parquet::file::serialized_reader::SerializedFileReader;
use parquet::file::writer::SerializedFileWriter;
use parquet::schema::types::Type;
use std::fs::File;
use std::sync::Arc;
let field = Type::primitive_type_builder("c", PhysicalType::BYTE_ARRAY)
.with_repetition(Repetition::REQUIRED)
.with_converted_type(ConvertedType::DECIMAL)
.with_precision(8)
.with_scale(0)
.build()
.unwrap();
let schema = Arc::new(
Type::group_type_builder("schema")
.with_fields(vec![Arc::new(field)])
.build()
.unwrap(),
);
let file = File::create("/tmp/repro.parquet").unwrap();
let mut writer =
SerializedFileWriter::new(file, schema,
Arc::new(WriterProperties::builder().build())).unwrap();
let mut rg = writer.next_row_group().unwrap();
let mut col = rg.next_column().unwrap().unwrap();
// minimal big-endian two's-complement: 255 and 32768
let values = vec![
ByteArray::from(vec![0x00u8, 0xFF]), // 255
ByteArray::from(vec![0x00u8, 0x80, 0x00]), // 32768
];
col.typed::<ByteArrayType>().write_batch(&values, None, None).unwrap();
col.close().unwrap();
rg.close().unwrap();
writer.close().unwrap();
let reader =
SerializedFileReader::new(File::open("/tmp/repro.parquet").unwrap()).unwrap();
let stats = reader.metadata().row_group(0).column(0).statistics().unwrap();
println!("{stats:?}");
// min: Some(b"\0\x80\0") (= 32768), max: Some(b"\0\xff") (= 255),
// max_value_exact: true, min_value_exact: true
// expected: min = 255, max = 32768
```
### Expected behavior
_No response_
### Additional context
_No response_
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