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ARROW-8426: [Rust] [Parquet] Add support for writing dictionary types #8291

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carols10cents wants to merge 1 commit into from
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ARROW-8426: [Rust] [Parquet] Add support for writing dictionary types #8291

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4 changes: 2 additions & 2 deletions rust/arrow/src/datatypes.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -181,8 +181,8 @@ pub struct Field {
name: String,
data_type: DataType,
nullable: bool,
dict_id: i64,
dict_is_ordered: bool,
pub(crate) dict_id: i64,
pub(crate) dict_is_ordered: bool,
}

pub trait ArrowNativeType:
Expand Down
105 changes: 81 additions & 24 deletions rust/arrow/src/ipc/convert.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -34,18 +34,8 @@ pub fn schema_to_fb(schema: &Schema) -> FlatBufferBuilder {

let mut fields = vec![];
for field in schema.fields() {
let fb_field_name = fbb.create_string(field.name().as_str());
let field_type = get_fb_field_type(field.data_type(), &mut fbb);
let mut field_builder = ipc::FieldBuilder::new(&mut fbb);
field_builder.add_name(fb_field_name);
field_builder.add_type_type(field_type.type_type);
field_builder.add_nullable(field.is_nullable());
match field_type.children {
None => {}
Some(children) => field_builder.add_children(children),
};
field_builder.add_type_(field_type.type_);
fields.push(field_builder.finish());
let fb_field = build_field(&mut fbb, field);
fields.push(fb_field);
}

let mut custom_metadata = vec![];
Expand Down Expand Up @@ -80,18 +70,8 @@ pub fn schema_to_fb_offset<'a: 'b, 'b>(
) -> WIPOffset<ipc::Schema<'b>> {
let mut fields = vec![];
for field in schema.fields() {
let fb_field_name = fbb.create_string(field.name().as_str());
let field_type = get_fb_field_type(field.data_type(), fbb);
let mut field_builder = ipc::FieldBuilder::new(fbb);
field_builder.add_name(fb_field_name);
field_builder.add_type_type(field_type.type_type);
field_builder.add_nullable(field.is_nullable());
match field_type.children {
None => {}
Some(children) => field_builder.add_children(children),
};
field_builder.add_type_(field_type.type_);
fields.push(field_builder.finish());
let fb_field = build_field(fbb, field);
fields.push(fb_field);
}

let mut custom_metadata = vec![];
Expand Down Expand Up @@ -333,6 +313,38 @@ pub(crate) struct FBFieldType<'b> {
pub(crate) children: Option<WIPOffset<Vector<'b, ForwardsUOffset<ipc::Field<'b>>>>>,
}

/// Create an IPC Field from an Arrow Field
pub(crate) fn build_field<'a: 'b, 'b>(
fbb: &mut FlatBufferBuilder<'a>,
field: &Field,
) -> WIPOffset<ipc::Field<'b>> {
let fb_field_name = fbb.create_string(field.name().as_str());
let field_type = get_fb_field_type(field.data_type(), fbb);

let fb_dictionary = if let Dictionary(index_type, _) = field.data_type() {
Some(get_fb_dictionary(
index_type,
field.dict_id,
field.dict_is_ordered,
fbb,
))
} else {
None
};

let mut field_builder = ipc::FieldBuilder::new(fbb);
field_builder.add_name(fb_field_name);
fb_dictionary.map(|dictionary| field_builder.add_dictionary(dictionary));
field_builder.add_type_type(field_type.type_type);
field_builder.add_nullable(field.is_nullable());
match field_type.children {
None => {}
Some(children) => field_builder.add_children(children),
};
field_builder.add_type_(field_type.type_);
field_builder.finish()
}

/// Get the IPC type of a data type
pub(crate) fn get_fb_field_type<'a: 'b, 'b>(
data_type: &DataType,
Expand Down Expand Up @@ -609,10 +621,45 @@ pub(crate) fn get_fb_field_type<'a: 'b, 'b>(
children: Some(fbb.create_vector(&children[..])),
}
}
Dictionary(_, value_type) => {
// In this library, the dictionary "type" is a logical construct. Here we
// pass through to the value type, as we've already captured the index
// type in the DictionaryEncoding metadata in the parent field
get_fb_field_type(value_type, fbb)
}
t => unimplemented!("Type {:?} not supported", t),
}
}

/// Create an IPC dictionary encoding
pub(crate) fn get_fb_dictionary<'a: 'b, 'b>(
index_type: &DataType,
dict_id: i64,
dict_is_ordered: bool,
fbb: &mut FlatBufferBuilder<'a>,
) -> WIPOffset<ipc::DictionaryEncoding<'b>> {
// We assume that the dictionary index type (as an integer) has already been
// validated elsewhere, and can safely assume we are dealing with signed
// integers
let mut index_builder = ipc::IntBuilder::new(fbb);
index_builder.add_is_signed(true);
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@nevi-me nevi-me Sep 29, 2020

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Although signed indices are preferred, we do support unsigned dictionary indices in the data types, so we might need to populate this based on the index_type

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@nevi-me nevi-me Oct 3, 2020

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@carols10cents we can address this in future, I'm merging this

match *index_type {
Int8 => index_builder.add_bitWidth(8),
Int16 => index_builder.add_bitWidth(16),
Int32 => index_builder.add_bitWidth(32),
Int64 => index_builder.add_bitWidth(64),
_ => {}
}
let index_builder = index_builder.finish();

let mut builder = ipc::DictionaryEncodingBuilder::new(fbb);
builder.add_id(dict_id);
builder.add_indexType(index_builder);
builder.add_isOrdered(dict_is_ordered);

builder.finish()
}

#[cfg(test)]
mod tests {
use super::*;
Expand Down Expand Up @@ -714,6 +761,16 @@ mod tests {
false,
),
Field::new("struct<>", DataType::Struct(vec![]), true),
Field::new_dict(
"dictionary<int32, utf8>",
DataType::Dictionary(
Box::new(DataType::Int32),
Box::new(DataType::Utf8),
),
true,
123,
true,
),
],
md,
);
Expand Down
20 changes: 10 additions & 10 deletions rust/parquet/src/arrow/schema.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1396,16 +1396,16 @@ mod tests {
// Field::new("c28", DataType::Duration(TimeUnit::Millisecond), false),
// Field::new("c29", DataType::Duration(TimeUnit::Microsecond), false),
// Field::new("c30", DataType::Duration(TimeUnit::Nanosecond), false),
// Field::new_dict(
// "c31",
// DataType::Dictionary(
// Box::new(DataType::Int32),
// Box::new(DataType::Utf8),
// ),
// true,
// 123,
// true,
// ),
Field::new_dict(
"c31",
DataType::Dictionary(
Box::new(DataType::Int32),
Box::new(DataType::Utf8),
),
true,
123,
true,
),
Field::new("c32", DataType::LargeBinary, true),
Field::new("c33", DataType::LargeUtf8, true),
Field::new(
Expand Down