pub struct ParentState<'a, S: BuilderSpecificState> {
value_builder: &'a mut ValueBuilder,
saved_value_builder_offset: usize,
metadata_builder: &'a mut dyn MetadataBuilder,
saved_metadata_builder_dict_size: usize,
builder_state: S,
finished: bool,
}
Expand description
Tracks information needed to correctly finalize a nested builder.
A child builder has no effect on its parent unless/until its finalize
method is called, at
which point the child appends the new value to the parent. As a (desirable) side effect,
creating a parent state instance captures mutable references to a subset of the parent’s fields,
rendering the parent object completely unusable until the parent state goes out of scope. This
ensures that at most one child builder can exist at a time.
The redundancy in value_builder
and metadata_builder
is because all the references come from
the parent, and we cannot “split” a mutable reference across two objects (parent state and the
child builder that uses it). So everything has to be here.
Fields§
§value_builder: &'a mut ValueBuilder
§saved_value_builder_offset: usize
§metadata_builder: &'a mut dyn MetadataBuilder
§saved_metadata_builder_dict_size: usize
§builder_state: S
§finished: bool
Implementations§
Source§impl<'a, S: BuilderSpecificState> ParentState<'a, S>
impl<'a, S: BuilderSpecificState> ParentState<'a, S>
Sourcepub fn new(
value_builder: &'a mut ValueBuilder,
metadata_builder: &'a mut dyn MetadataBuilder,
builder_state: S,
) -> Self
pub fn new( value_builder: &'a mut ValueBuilder, metadata_builder: &'a mut dyn MetadataBuilder, builder_state: S, ) -> Self
Creates a new ParentState instance. The value and metadata builder
state is checkpointed and will roll back on drop, unless Self::finish
is called. The
builder-specific state is governed by its own finish
and rollback
calls.
Sourcepub fn finish(&mut self)
pub fn finish(&mut self)
Marks the insertion as having succeeded and invokes
BuilderSpecificState::finish
. Internal state will no longer roll back on drop.
fn rollback(&mut self)
fn value_builder(&mut self) -> &mut ValueBuilder
fn metadata_builder(&mut self) -> &mut dyn MetadataBuilder
Source§impl<'a> ParentState<'a, ()>
impl<'a> ParentState<'a, ()>
Sourcepub fn variant(
value_builder: &'a mut ValueBuilder,
metadata_builder: &'a mut dyn MetadataBuilder,
) -> Self
pub fn variant( value_builder: &'a mut ValueBuilder, metadata_builder: &'a mut dyn MetadataBuilder, ) -> Self
Creates a new instance suitable for a top-level variant builder
(e.g. VariantBuilder
). The value and metadata builder state is checkpointed and will
roll back on drop, unless Self::finish
is called.
Source§impl<'a> ParentState<'a, ListState<'a>>
impl<'a> ParentState<'a, ListState<'a>>
Sourcepub fn list(
value_builder: &'a mut ValueBuilder,
metadata_builder: &'a mut dyn MetadataBuilder,
offsets: &'a mut Vec<usize>,
saved_parent_value_builder_offset: usize,
) -> Self
pub fn list( value_builder: &'a mut ValueBuilder, metadata_builder: &'a mut dyn MetadataBuilder, offsets: &'a mut Vec<usize>, saved_parent_value_builder_offset: usize, ) -> Self
Creates a new instance suitable for a ListBuilder
. The value and metadata builder state
is checkpointed and will roll back on drop, unless Self::finish
is called. The new
element’s offset is also captured eagerly and will also roll back if not finished.
Source§impl<'a> ParentState<'a, ObjectState<'a>>
impl<'a> ParentState<'a, ObjectState<'a>>
Sourcepub fn try_object(
value_builder: &'a mut ValueBuilder,
metadata_builder: &'a mut dyn MetadataBuilder,
fields: &'a mut IndexMap<u32, usize>,
saved_parent_value_builder_offset: usize,
field_name: &str,
validate_unique_fields: bool,
) -> Result<Self, ArrowError>
pub fn try_object( value_builder: &'a mut ValueBuilder, metadata_builder: &'a mut dyn MetadataBuilder, fields: &'a mut IndexMap<u32, usize>, saved_parent_value_builder_offset: usize, field_name: &str, validate_unique_fields: bool, ) -> Result<Self, ArrowError>
Creates a new instance suitable for an ObjectBuilder
. The value and metadata builder state
is checkpointed and will roll back on drop, unless Self::finish
is called. The new
field’s name and offset are also captured eagerly and will also roll back if not finished.
The call fails if the field name is invalid (e.g. because it duplicates an existing field).
Trait Implementations§
Source§impl<'a, S: Debug + BuilderSpecificState> Debug for ParentState<'a, S>
impl<'a, S: Debug + BuilderSpecificState> Debug for ParentState<'a, S>
Source§impl<S: BuilderSpecificState> Drop for ParentState<'_, S>
Automatically rolls back any unfinished ParentState
.
impl<S: BuilderSpecificState> Drop for ParentState<'_, S>
Automatically rolls back any unfinished ParentState
.