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[Variant] Caller provides ParentState to ValueBuilder methods #8189

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Merged
merged 6 commits into from
Aug 21, 2025
Merged

[Variant] Caller provides ParentState to ValueBuilder methods #8189

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337600e
[Variant] ParentState handles finish/rollback for builders
scovich Aug 20, 2025
9eb3c68
Add fallible methods to VariantBuilderExt
scovich Aug 20, 2025
2aa1472
Merge remote-tracking branch 'oss/main' into value-builder-parent-state
scovich Aug 20, 2025
eaf2de2
address reviews
scovich Aug 20, 2025
7171126
[Variant] Caller provides ParentState to ValueBuilder methods
scovich Aug 20, 2025
7a45f75
Merge remote-tracking branch 'oss/main' into value-builder-parent-sta…
scovich Aug 21, 2025
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193 changes: 81 additions & 112 deletions parquet-variant/src/builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -251,8 +251,8 @@ impl ValueBuilder {
self.append_slice(value.as_bytes());
}

fn append_object(&mut self, metadata_builder: &mut MetadataBuilder, obj: VariantObject) {
let mut object_builder = self.new_object(metadata_builder);
fn append_object(state: ParentState<'_>, obj: VariantObject) {
let mut object_builder = ObjectBuilder::new(state, false);

for (field_name, value) in obj.iter() {
object_builder.insert(field_name, value);
Expand All @@ -261,37 +261,27 @@ impl ValueBuilder {
object_builder.finish().unwrap();
}

fn try_append_object(
&mut self,
metadata_builder: &mut MetadataBuilder,
obj: VariantObject,
) -> Result<(), ArrowError> {
let mut object_builder = self.new_object(metadata_builder);
fn try_append_object(state: ParentState<'_>, obj: VariantObject) -> Result<(), ArrowError> {
let mut object_builder = ObjectBuilder::new(state, false);

for res in obj.iter_try() {
let (field_name, value) = res?;
object_builder.try_insert(field_name, value)?;
}

object_builder.finish()?;

Ok(())
object_builder.finish()
}

fn append_list(&mut self, metadata_builder: &mut MetadataBuilder, list: VariantList) {
let mut list_builder = self.new_list(metadata_builder);
fn append_list(state: ParentState<'_>, list: VariantList) {
let mut list_builder = ListBuilder::new(state, false);
for value in list.iter() {
list_builder.append_value(value);
}
list_builder.finish();
}

fn try_append_list(
&mut self,
metadata_builder: &mut MetadataBuilder,
list: VariantList,
) -> Result<(), ArrowError> {
let mut list_builder = self.new_list(metadata_builder);
fn try_append_list(state: ParentState<'_>, list: VariantList) -> Result<(), ArrowError> {
let mut list_builder = ListBuilder::new(state, false);
for res in list.iter_try() {
let value = res?;
list_builder.try_append_value(value)?;
Expand All @@ -306,93 +296,80 @@ impl ValueBuilder {
self.0.len()
}

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

/// Appends a variant to the builder.
///
/// # Panics
///
/// This method will panic if the variant contains duplicate field names in objects
/// when validation is enabled. For a fallible version, use [`ValueBuilder::try_append_variant`]
fn append_variant<'m, 'd>(
&mut self,
variant: Variant<'m, 'd>,
metadata_builder: &mut MetadataBuilder,
) {
fn append_variant(mut state: ParentState<'_>, variant: Variant<'_, '_>) {
let builder = state.value_builder();
match variant {
Variant::Null => self.append_null(),
Variant::BooleanTrue => self.append_bool(true),
Variant::BooleanFalse => self.append_bool(false),
Variant::Int8(v) => self.append_int8(v),
Variant::Int16(v) => self.append_int16(v),
Variant::Int32(v) => self.append_int32(v),
Variant::Int64(v) => self.append_int64(v),
Variant::Date(v) => self.append_date(v),
Variant::TimestampMicros(v) => self.append_timestamp_micros(v),
Variant::TimestampNtzMicros(v) => self.append_timestamp_ntz_micros(v),
Variant::TimestampNanos(v) => self.append_timestamp_nanos(v),
Variant::TimestampNtzNanos(v) => self.append_timestamp_ntz_nanos(v),
Variant::Decimal4(decimal4) => self.append_decimal4(decimal4),
Variant::Decimal8(decimal8) => self.append_decimal8(decimal8),
Variant::Decimal16(decimal16) => self.append_decimal16(decimal16),
Variant::Float(v) => self.append_float(v),
Variant::Double(v) => self.append_double(v),
Variant::Binary(v) => self.append_binary(v),
Variant::String(s) => self.append_string(s),
Variant::ShortString(s) => self.append_short_string(s),
Variant::Uuid(v) => self.append_uuid(v),
Variant::Object(obj) => self.append_object(metadata_builder, obj),
Variant::List(list) => self.append_list(metadata_builder, list),
Variant::Time(v) => self.append_time_micros(v),
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FYI I moved Time up by Date for better logical grouping.

(again below)

Variant::Null => builder.append_null(),
Variant::BooleanTrue => builder.append_bool(true),
Variant::BooleanFalse => builder.append_bool(false),
Variant::Int8(v) => builder.append_int8(v),
Variant::Int16(v) => builder.append_int16(v),
Variant::Int32(v) => builder.append_int32(v),
Variant::Int64(v) => builder.append_int64(v),
Variant::Date(v) => builder.append_date(v),
Variant::Time(v) => builder.append_time_micros(v),
Variant::TimestampMicros(v) => builder.append_timestamp_micros(v),
Variant::TimestampNtzMicros(v) => builder.append_timestamp_ntz_micros(v),
Variant::TimestampNanos(v) => builder.append_timestamp_nanos(v),
Variant::TimestampNtzNanos(v) => builder.append_timestamp_ntz_nanos(v),
Variant::Decimal4(decimal4) => builder.append_decimal4(decimal4),
Variant::Decimal8(decimal8) => builder.append_decimal8(decimal8),
Variant::Decimal16(decimal16) => builder.append_decimal16(decimal16),
Variant::Float(v) => builder.append_float(v),
Variant::Double(v) => builder.append_double(v),
Variant::Binary(v) => builder.append_binary(v),
Variant::String(s) => builder.append_string(s),
Variant::ShortString(s) => builder.append_short_string(s),
Variant::Uuid(v) => builder.append_uuid(v),
Variant::Object(obj) => return Self::append_object(state, obj),
Variant::List(list) => return Self::append_list(state, list),
}
state.finish();
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Not sure if it's better to move this line to the caller, the finish now is associated with ParentState, maybe creating and finishing in the same place is better?

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The nested builders have to take ownership of their parent state (else many call sites would illegally return a reference to a temporary). So here, we have an owned value that sometimes needs finish and sometimes doesn't. Returning Option<ParentState<'_>> seems ugly and annoying?

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If there is interest in trying the alternative, how about we make a follow on PR

}

/// Appends a variant to the builder
fn try_append_variant<'m, 'd>(
&mut self,
variant: Variant<'m, 'd>,
metadata_builder: &mut MetadataBuilder,
/// Tries to append a variant to the provided [`ParentState`] instance.
///
/// The attempt fails if the variant contains duplicate field names in objects when validation
/// is enabled.
pub fn try_append_variant(
mut state: ParentState<'_>,
variant: Variant<'_, '_>,
) -> Result<(), ArrowError> {
let builder = state.value_builder();
match variant {
Variant::Null => self.append_null(),
Variant::BooleanTrue => self.append_bool(true),
Variant::BooleanFalse => self.append_bool(false),
Variant::Int8(v) => self.append_int8(v),
Variant::Int16(v) => self.append_int16(v),
Variant::Int32(v) => self.append_int32(v),
Variant::Int64(v) => self.append_int64(v),
Variant::Date(v) => self.append_date(v),
Variant::TimestampMicros(v) => self.append_timestamp_micros(v),
Variant::TimestampNtzMicros(v) => self.append_timestamp_ntz_micros(v),
Variant::TimestampNanos(v) => self.append_timestamp_nanos(v),
Variant::TimestampNtzNanos(v) => self.append_timestamp_ntz_nanos(v),
Variant::Decimal4(decimal4) => self.append_decimal4(decimal4),
Variant::Decimal8(decimal8) => self.append_decimal8(decimal8),
Variant::Decimal16(decimal16) => self.append_decimal16(decimal16),
Variant::Float(v) => self.append_float(v),
Variant::Double(v) => self.append_double(v),
Variant::Binary(v) => self.append_binary(v),
Variant::Uuid(v) => self.append_uuid(v),
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FYI I moved Uuid below ShortString to match append_variant above

Variant::String(s) => self.append_string(s),
Variant::ShortString(s) => self.append_short_string(s),
Variant::Object(obj) => self.try_append_object(metadata_builder, obj)?,
Variant::List(list) => self.try_append_list(metadata_builder, list)?,
Variant::Time(v) => self.append_time_micros(v),
Variant::Null => builder.append_null(),
Variant::BooleanTrue => builder.append_bool(true),
Variant::BooleanFalse => builder.append_bool(false),
Variant::Int8(v) => builder.append_int8(v),
Variant::Int16(v) => builder.append_int16(v),
Variant::Int32(v) => builder.append_int32(v),
Variant::Int64(v) => builder.append_int64(v),
Variant::Date(v) => builder.append_date(v),
Variant::Time(v) => builder.append_time_micros(v),
Variant::TimestampMicros(v) => builder.append_timestamp_micros(v),
Variant::TimestampNtzMicros(v) => builder.append_timestamp_ntz_micros(v),
Variant::TimestampNanos(v) => builder.append_timestamp_nanos(v),
Variant::TimestampNtzNanos(v) => builder.append_timestamp_ntz_nanos(v),
Variant::Decimal4(decimal4) => builder.append_decimal4(decimal4),
Variant::Decimal8(decimal8) => builder.append_decimal8(decimal8),
Variant::Decimal16(decimal16) => builder.append_decimal16(decimal16),
Variant::Float(v) => builder.append_float(v),
Variant::Double(v) => builder.append_double(v),
Variant::Binary(v) => builder.append_binary(v),
Variant::String(s) => builder.append_string(s),
Variant::ShortString(s) => builder.append_short_string(s),
Variant::Uuid(v) => builder.append_uuid(v),
Variant::Object(obj) => return Self::try_append_object(state, obj),
Variant::List(list) => return Self::try_append_list(state, list),
}

state.finish();
Ok(())
}

Expand Down Expand Up @@ -1224,21 +1201,17 @@ impl VariantBuilder {
/// builder.append_value(42i8);
/// ```
pub fn append_value<'m, 'd, T: Into<Variant<'m, 'd>>>(&mut self, value: T) {
let variant = value.into();
self.value_builder
.append_variant(variant, &mut self.metadata_builder);
let state = ParentState::variant(&mut self.value_builder, &mut self.metadata_builder);
ValueBuilder::append_variant(state, value.into())
}

/// Append a value to the builder.
pub fn try_append_value<'m, 'd, T: Into<Variant<'m, 'd>>>(
&mut self,
value: T,
) -> Result<(), ArrowError> {
let variant = value.into();
self.value_builder
.try_append_variant(variant, &mut self.metadata_builder)?;

Ok(())
let state = ParentState::variant(&mut self.value_builder, &mut self.metadata_builder);
ValueBuilder::try_append_variant(state, value.into())
}

/// Finish the builder and return the metadata and value buffers.
Expand Down Expand Up @@ -1326,19 +1299,17 @@ impl<'a> ListBuilder<'a> {
/// This method will panic if the variant contains duplicate field names in objects
/// when validation is enabled. For a fallible version, use [`ListBuilder::try_append_value`].
pub fn append_value<'m, 'd, T: Into<Variant<'m, 'd>>>(&mut self, value: T) {
self.try_append_value(value).unwrap();
let (state, _) = self.parent_state();
ValueBuilder::append_variant(state, value.into())
}

/// Appends a new primitive value to this list
pub fn try_append_value<'m, 'd, T: Into<Variant<'m, 'd>>>(
&mut self,
value: T,
) -> Result<(), ArrowError> {
let (mut state, _) = self.parent_state();
let (value_builder, metadata_builder) = state.value_and_metadata_builders();
value_builder.try_append_variant(value.into(), metadata_builder)?;
state.finish();
Ok(())
let (state, _) = self.parent_state();
ValueBuilder::try_append_variant(state, value.into())
}

/// Builder-style API for appending a value to the list and returning self to enable method chaining.
Expand Down Expand Up @@ -1436,7 +1407,8 @@ impl<'a> ObjectBuilder<'a> {
/// This method will panic if the variant contains duplicate field names in objects
/// when validation is enabled. For a fallible version, use [`ObjectBuilder::try_insert`]
pub fn insert<'m, 'd, T: Into<Variant<'m, 'd>>>(&mut self, key: &str, value: T) {
self.try_insert(key, value).unwrap();
let (state, _) = self.parent_state(key).unwrap();
ValueBuilder::append_variant(state, value.into())
}

/// Add a field with key and value to the object
Expand All @@ -1453,11 +1425,8 @@ impl<'a> ObjectBuilder<'a> {
key: &str,
value: T,
) -> Result<(), ArrowError> {
let (mut state, _) = self.parent_state(key)?;
let (value_builder, metadata_builder) = state.value_and_metadata_builders();
value_builder.try_append_variant(value.into(), metadata_builder)?;
state.finish();
Ok(())
let (state, _) = self.parent_state(key)?;
ValueBuilder::try_append_variant(state, value.into())
}

/// Builder style API for adding a field with key and value to the object
Expand Down
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