Struct ShreddingState 

pub struct ShreddingState {
    value: ArrayRef,
    typed_value: Option<ArrayRef>,
}

Represents the shredding state of a VariantArray

VariantArrays can be shredded according to the Parquet Variant Shredding Spec. Shredding means that the actual value is stored in a typed typed_field instead of the generic value field.

The value column is always present (the spec requires writers to emit it); typed_value is optional. Values in the two columns must be interpreted according to the following table (see Parquet Variant Shredding Spec for more details):

value	typed_value	Meaning
NULL	NULL	The value is missing; only valid for shredded object fields
non-NULL	NULL	The value is present and may be any type, including [Variant::Null]
NULL	non-NULL	The value is present and is the shredded type
non-NULL	non-NULL	The value is present and is a partially shredded object

Applying the above rules to entire columns, we obtain the following:

value	typed_value	Meaning
exists	–	Unshredded: If present, the value may be any type, including [Variant::Null]
exists	exists	Shredded: perfectly if value is all-null, otherwise imperfectly

Note the spec requires the value column to always be present in the schema; structs without one are rejected (see https://github.com/apache/arrow-rs/issues/10306).

NOTE: Partial shredding is a row-wise situation that can arise under imperfect shredding (a column-wise situation): When both columns exist (imperfect shredding) and the typed_value column is a struct, then both columns can be non-NULL for the same row if value is a variant object (partial shredding).

Fields

value: ArrayRef

typed_value: Option<ArrayRef>

Implementations

impl ShreddingState

pub fn new(value: ArrayRef, typed_value: Option<ArrayRef>) -> Self

Create a new ShreddingState from the given value and typed_value fields

Note you can create a ShreddingState from a &[StructArray] using ShreddingState::try_from(&struct_array), for example:

let struct_array: StructArray = get_struct_array();
let shredding_state = ShreddingState::try_from(&struct_array).unwrap();

pub fn value_column(&self) -> &ArrayRef

Return a reference to the value column

pub fn typed_value_column(&self) -> Option<&ArrayRef>

Return a reference to the typed_value column, if present

pub fn slice(&self, offset: usize, length: usize) -> Self

Slice all the underlying arrays

Trait Implementations

impl Clone for ShreddingState

fn clone(&self) -> ShreddingState

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ShreddingState

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl TryFrom<&StructArray> for ShreddingState

type Error = ArrowError

The type returned in the event of a conversion error.

fn try_from(inner_struct: &StructArray) -> Result<Self>

Performs the conversion.