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Unify nested variant handling #5

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Merged
friendlymatthew merged 2 commits into from
Jul 14, 2025
Merged

Unify nested variant handling #5

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78dc655
Unify nested variant handling
alamb Jul 14, 2025
28832d5
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alamb Jul 14, 2025
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131 changes: 42 additions & 89 deletions parquet-variant/src/builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,8 +16,7 @@
// under the License.
use crate::decoder::{VariantBasicType, VariantPrimitiveType};
use crate::{
ShortString, Variant, VariantDecimal16, VariantDecimal4, VariantDecimal8, VariantList,
VariantObject,
ShortString, Variant, VariantDecimal16, VariantDecimal4, VariantDecimal8,
};
use arrow_schema::ArrowError;
use indexmap::{IndexMap, IndexSet};
Expand Down Expand Up @@ -195,7 +194,28 @@ impl ValueBuffer {
self.0.len()
}

fn append_variant<'m, 'd>(&mut self, variant: Variant<'m, 'd>) {
fn new_object<'a>(&'a mut self, metadata_builder: &'a mut MetadataBuilder) -> ObjectBuilder<'a> {
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@alamb alamb Jul 14, 2025

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This is the major change - move the low level appending to the ValueBuffer itself

Then all the recursion seems to fall into place

let parent_state = ParentState::Variant {
buffer: self,
metadata_builder,
};
let validate_unique_fields = false;
ObjectBuilder::new(parent_state, validate_unique_fields)
}

fn new_list<'a>(
&'a mut self,
metadata_builder: &'a mut MetadataBuilder,
) -> ListBuilder<'a> {
let parent_state = ParentState::Variant {
buffer: self,
metadata_builder,
};
let validate_unique_fields = false;
ListBuilder::new(parent_state, validate_unique_fields)
}

fn append_variant<'m, 'd>(&mut self, variant: Variant<'m, 'd>, metadata_builder: &mut MetadataBuilder) {
match variant {
Variant::Null => self.append_null(),
Variant::BooleanTrue => self.append_bool(true),
Expand All @@ -215,14 +235,25 @@ impl ValueBuffer {
Variant::Binary(v) => self.append_binary(v),
Variant::String(s) => self.append_string(s),
Variant::ShortString(s) => self.append_short_string(s),
_ => unreachable!("Objects and lists must be appended using VariantBuilder::append_object and VariantBuilder::append_list"),
Variant::Object(obj) => {
let mut object_builder = self.new_object(metadata_builder);
for (field_name, value) in obj.iter() {
object_builder.insert(field_name, value);
}
// TODO propagate error
object_builder.finish().unwrap();
}
Variant::List(list) => {
let mut list_builder = self.new_list(metadata_builder);
for value in list.iter() {
list_builder.append_value(value);
}
// TOOD propagate error
list_builder.finish();
}
}
}

fn append_non_nested_value<'m, 'd, T: Into<Variant<'m, 'd>>>(&mut self, value: T) {
self.append_variant(value.into());
}

/// Writes out the header byte for a variant object or list
fn append_header(&mut self, header_byte: u8, is_large: bool, num_items: usize) {
let buf = self.inner_mut();
Expand Down Expand Up @@ -699,79 +730,6 @@ impl VariantBuilder {
ObjectBuilder::new(parent_state, validate_unique_fields)
}

/// Appends a [`VariantObject`] to the builder.
///
/// # Panics
/// Will panic if the appended object has duplicate field names or any nested validation fails.
/// Use `try_append_object` if you need full validation for untrusted data.
pub fn append_object<'m, 'v>(&mut self, object: VariantObject<'m, 'v>) {
let (parent_state, validate_unique_fields) = self.parent_state();

let mut obj_builder = ObjectBuilder::new(parent_state, validate_unique_fields);

for (field_name, variant) in object.iter() {
obj_builder.insert(field_name, variant);
}

obj_builder.finish().unwrap();
}

/// Appends a [`VariantObject`] to the builder with full validation during iteration.
///
/// Recursively validates all nested variants in the object during iteration.
pub fn try_append_object<'m, 'v>(
&mut self,
object: VariantObject<'m, 'v>,
) -> Result<(), ArrowError> {
let (parent_state, validate_unique_fields) = self.parent_state();

let mut obj_builder = ObjectBuilder::new(parent_state, validate_unique_fields);

for res in object.iter_try() {
let (field_name, variant) = res?;

obj_builder.insert(field_name, variant);
}

obj_builder.finish()?;

Ok(())
}

/// Appends a [`VariantList`] to the builder.
///
/// # Panics
/// Will panic if any nested validation fails during list iteration.
/// Use `try_append_list` if you need full validation for untrusted data.
pub fn append_list<'m, 'v>(&mut self, list: VariantList<'m, 'v>) {
let (parent_state, validate_unique_fields) = self.parent_state();

let mut list_builder = ListBuilder::new(parent_state, validate_unique_fields);

for variant in list.iter() {
list_builder.append_value(variant);
}

list_builder.finish();
}

/// Appends a [`VariantList`] to the builder with full validation during iteration.
///
/// Recursively validates all nested variants in the list during iteration.
pub fn try_append_list<'m, 'v>(&mut self, list: VariantList<'m, 'v>) -> Result<(), ArrowError> {
let (parent_state, validate_unique_fields) = self.parent_state();

let mut list_builder = ListBuilder::new(parent_state, validate_unique_fields);

for variant in list.iter_try() {
list_builder.append_value(variant?);
}

list_builder.finish();

Ok(())
}

/// Append a non-nested value to the builder.
///
/// # Example
Expand All @@ -783,12 +741,7 @@ impl VariantBuilder {
/// ```
pub fn append_value<'m, 'd, T: Into<Variant<'m, 'd>>>(&mut self, value: T) {
let variant = value.into();

match variant {
Variant::Object(obj) => self.append_object(obj),
Variant::List(list) => self.append_list(list),
primitive => self.buffer.append_variant(primitive),
}
self.buffer.append_variant(variant, &mut self.metadata_builder);
}

/// Finish the builder and return the metadata and value buffers.
Expand Down Expand Up @@ -855,7 +808,7 @@ impl<'a> ListBuilder<'a> {
/// Appends a new primitive value to this list
pub fn append_value<'m, 'd, T: Into<Variant<'m, 'd>>>(&mut self, value: T) {
self.offsets.push(self.buffer.offset());
self.buffer.append_non_nested_value(value);
self.buffer.append_variant(value.into(), self.parent_state.metadata_builder())
}

/// Finalizes this list and appends it to its parent, which otherwise remains unmodified.
Expand Down Expand Up @@ -927,7 +880,7 @@ impl<'a> ObjectBuilder<'a> {
self.duplicate_fields.insert(field_id);
}

self.buffer.append_non_nested_value(value);
self.buffer.append_variant(value.into(), metadata_builder)
}

/// Enables validation for unique field keys when inserting into this object.
Expand Down
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