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Allow reading Parquet maps that lack a values field #6730

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Allow reading Parquet maps that lack a values field #6730

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68 changes: 68 additions & 0 deletions parquet/src/arrow/arrow_reader/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4065,4 +4065,72 @@ mod tests {
}
}
}

#[test]
fn test_map_no_value() {
let schema = "
message spark_schema {
REQUIRED group my_map (MAP) {
REPEATED group key_value {
REQUIRED INT32 key;
}
}
REQUIRED group my_list (LIST) {
REPEATED group list {
REQUIRED INT32 element;
}
}
}
";
let schema = Arc::new(parse_message_type(schema).unwrap());

// Write Parquet file to buffer
let mut buffer: Vec<u8> = Vec::new();
let mut file_writer =
SerializedFileWriter::new(&mut buffer, schema, Default::default()).unwrap();
let mut row_group_writer = file_writer.next_row_group().unwrap();

// Write column my_map.key_value.key
let mut column_writer = row_group_writer.next_column().unwrap().unwrap();
column_writer
.typed::<Int32Type>()
.write_batch(
&[1, 2, 3, 4, 5, 6, 7, 8, 9],
Some(&[1, 1, 1, 1, 1, 1, 1, 1, 1]),
Some(&[0, 1, 1, 0, 1, 1, 0, 1, 1]),
)
.unwrap();
column_writer.close().unwrap();

// Write column my_list.list.element
let mut column_writer = row_group_writer.next_column().unwrap().unwrap();
column_writer
.typed::<Int32Type>()
.write_batch(
&[1, 2, 3, 4, 5, 6, 7, 8, 9],
Some(&[1, 1, 1, 1, 1, 1, 1, 1, 1]),
Some(&[0, 1, 1, 0, 1, 1, 0, 1, 1]),
)
.unwrap();
column_writer.close().unwrap();

// Finalize Parquet file
row_group_writer.close().unwrap();
file_writer.close().unwrap();
assert_eq!(&buffer[0..4], b"PAR1");

// Read Parquet file from buffer
let mut reader = ParquetRecordBatchReaderBuilder::try_new(Bytes::from(buffer))
.unwrap()
.build()
.unwrap();
let out = reader.next().unwrap().unwrap();
assert_eq!(out.num_rows(), 3);
assert_eq!(out.num_columns(), 2);
// map and list columns should now be equivalent
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So this means the parquet reader will read MAP without values as an ListArray -- I think this seems like the intention so 👍

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Yes, because an arrow map must have non-null values IIUC.

let c0 = out.column(0).as_list::<i32>();
let c1 = out.column(1).as_list::<i32>();
assert_eq!(c0.len(), c1.len());
c0.iter().zip(c1.iter()).for_each(|(l, r)| assert_eq!(l, r));
}
}
7 changes: 6 additions & 1 deletion parquet/src/arrow/schema/complex.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -271,8 +271,13 @@ impl Visitor {
return Err(arrow_err!("Child of map field must be repeated"));
}

// According to the specification the values are optional (#1642).
// In this case, return the keys as a list.
if map_key_value.get_fields().len() == 1 {
return self.visit_list(map_type, context);
}

if map_key_value.get_fields().len() != 2 {
// According to the specification the values are optional (#1642)
return Err(arrow_err!(
"Child of map field must have two children, found {}",
map_key_value.get_fields().len()
Expand Down
132 changes: 107 additions & 25 deletions parquet/src/record/reader.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -217,11 +217,15 @@ impl TreeBuilder {
Repetition::REPEATED,
"Invalid map type: {field:?}"
);
assert_eq!(
key_value_type.get_fields().len(),
2,
"Invalid map type: {field:?}"
);
// Parquet spec allows no value. In that case treat as a list. #1642
if key_value_type.get_fields().len() != 1 {
// If not a list, then there can only be 2 fields in the struct
assert_eq!(
key_value_type.get_fields().len(),
2,
"Invalid map type: {field:?}"
);
}

path.push(String::from(key_value_type.name()));

Expand All @@ -239,25 +243,35 @@ impl TreeBuilder {
row_group_reader,
)?;

let value_type = &key_value_type.get_fields()[1];
let value_reader = self.reader_tree(
value_type.clone(),
path,
curr_def_level + 1,
curr_rep_level + 1,
paths,
row_group_reader,
)?;
if key_value_type.get_fields().len() == 1 {
path.pop();
Reader::RepeatedReader(
field,
curr_def_level,
curr_rep_level,
Box::new(key_reader),
)
} else {
let value_type = &key_value_type.get_fields()[1];
let value_reader = self.reader_tree(
value_type.clone(),
path,
curr_def_level + 1,
curr_rep_level + 1,
paths,
row_group_reader,
)?;

path.pop();
path.pop();

Reader::KeyValueReader(
field,
curr_def_level,
curr_rep_level,
Box::new(key_reader),
Box::new(value_reader),
)
Reader::KeyValueReader(
field,
curr_def_level,
curr_rep_level,
Box::new(key_reader),
Box::new(value_reader),
)
}
}
// A repeated field that is neither contained by a `LIST`- or
// `MAP`-annotated group nor annotated by `LIST` or `MAP`
Expand Down Expand Up @@ -813,7 +827,7 @@ impl Iterator for ReaderIter {
mod tests {
use super::*;

use crate::data_type::Int64Type;
use crate::data_type::{Int32Type, Int64Type};
use crate::file::reader::SerializedFileReader;
use crate::file::writer::SerializedFileWriter;
use crate::record::api::RowAccessor;
Expand Down Expand Up @@ -1459,8 +1473,7 @@ mod tests {
}

#[test]
#[should_panic(expected = "Invalid map type")]
fn test_file_reader_rows_invalid_map_type() {
fn test_file_reader_rows_nested_map_type() {
let schema = "
message spark_schema {
OPTIONAL group a (MAP) {
Expand Down Expand Up @@ -1823,6 +1836,75 @@ mod tests {
assert_eq!(rows, expected_rows);
}

#[test]
fn test_map_no_value() {
let schema = "
message spark_schema {
REQUIRED group my_map (MAP) {
REPEATED group key_value {
REQUIRED INT32 key;
}
}
REQUIRED group my_list (LIST) {
REPEATED group list {
REQUIRED INT32 element;
}
}
}
";
let schema = Arc::new(parse_message_type(schema).unwrap());

// Write Parquet file to buffer
//let mut buffer = std::fs::File::create("/Users/seidl/map_no_value.pq").unwrap();
let mut buffer: Vec<u8> = Vec::new();
let mut file_writer =
SerializedFileWriter::new(&mut buffer, schema, Default::default()).unwrap();
let mut row_group_writer = file_writer.next_row_group().unwrap();

// Write column my_map.key_value.key
let mut column_writer = row_group_writer.next_column().unwrap().unwrap();
column_writer
.typed::<Int32Type>()
.write_batch(
&[1, 2, 3, 4, 5, 6, 7, 8, 9],
Some(&[1, 1, 1, 1, 1, 1, 1, 1, 1]),
Some(&[0, 1, 1, 0, 1, 1, 0, 1, 1]),
)
.unwrap();
column_writer.close().unwrap();

// Write column my_list.list.element
let mut column_writer = row_group_writer.next_column().unwrap().unwrap();
column_writer
.typed::<Int32Type>()
.write_batch(
&[1, 2, 3, 4, 5, 6, 7, 8, 9],
Some(&[1, 1, 1, 1, 1, 1, 1, 1, 1]),
Some(&[0, 1, 1, 0, 1, 1, 0, 1, 1]),
)
.unwrap();
column_writer.close().unwrap();

// Finalize Parquet file
row_group_writer.close().unwrap();
file_writer.close().unwrap();
assert_eq!(&buffer[0..4], b"PAR1");

// Read Parquet file from buffer
let file_reader = SerializedFileReader::new(Bytes::from(buffer)).unwrap();
let rows: Vec<_> = file_reader
.get_row_iter(None)
.unwrap()
.map(|row| row.unwrap())
.collect();

// the two columns should be equivalent lists by this point
for row in rows {
let cols = row.into_columns();
assert_eq!(cols[0].1, cols[1].1);
}
}

fn test_file_reader_rows(file_name: &str, schema: Option<Type>) -> Result<Vec<Row>> {
let file = get_test_file(file_name);
let file_reader: Box<dyn FileReader> = Box::new(SerializedFileReader::new(file)?);
Expand Down
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