Struct StructArray

pub struct StructArray {
    len: usize,
    data_type: DataType,
    nulls: Option<NullBuffer>,
    fields: Vec<ArrayRef>,
}

An array of structs

Each child (called field) is represented by a separate array.

Comparison with RecordBatch

Both RecordBatch and StructArray represent a collection of columns / arrays with the same length.

However, there are a couple of key differences:

• StructArray can be nested within other Array, including itself
• RecordBatch can contain top-level metadata on its associated [Schema][arrow_schema::Schema]
• StructArray can contain top-level nulls, i.e. null
• RecordBatch can only represent nulls in its child columns, i.e. {"field": null}

StructArray is therefore a more general data container than RecordBatch, and as such code that needs to handle both will typically share an implementation in terms of StructArray and convert to/from RecordBatch as necessary.

From implementations are provided to facilitate this conversion, however, converting from a StructArray containing top-level nulls to a RecordBatch will panic, as there is no way to preserve them.

Example: Create an array from a vector of fields

use std::sync::Arc;
use arrow_array::{Array, ArrayRef, BooleanArray, Int32Array, StructArray};
use arrow_schema::{DataType, Field};

let boolean = Arc::new(BooleanArray::from(vec![false, false, true, true]));
let int = Arc::new(Int32Array::from(vec![42, 28, 19, 31]));

let struct_array = StructArray::from(vec![
    (
        Arc::new(Field::new("b", DataType::Boolean, false)),
        boolean.clone() as ArrayRef,
    ),
    (
        Arc::new(Field::new("c", DataType::Int32, false)),
        int.clone() as ArrayRef,
    ),
]);
assert_eq!(struct_array.column(0).as_ref(), boolean.as_ref());
assert_eq!(struct_array.column(1).as_ref(), int.as_ref());
assert_eq!(4, struct_array.len());
assert_eq!(0, struct_array.null_count());
assert_eq!(0, struct_array.offset());

Fields

len: usize

data_type: DataType

nulls: Option<NullBuffer>

fields: Vec<ArrayRef>

Implementations

impl StructArray

pub fn new( fields: Fields, arrays: Vec<ArrayRef>, nulls: Option<NullBuffer>, ) -> Self

Create a new StructArray from the provided parts, panicking on failure

Panics

Panics if Self::try_new returns an error

pub fn try_new( fields: Fields, arrays: Vec<ArrayRef>, nulls: Option<NullBuffer>, ) -> Result<Self, ArrowError>

Create a new StructArray from the provided parts, returning an error on failure

Errors

Errors if

• fields.len() != arrays.len()
• fields[i].data_type() != arrays[i].data_type()
• arrays[i].len() != arrays[j].len()
• arrays[i].len() != nulls.len()
• !fields[i].is_nullable() && !nulls.contains(arrays[i].nulls())

pub fn new_null(fields: Fields, len: usize) -> Self

Create a new StructArray of length len where all values are null

pub unsafe fn new_unchecked( fields: Fields, arrays: Vec<ArrayRef>, nulls: Option<NullBuffer>, ) -> Self

Create a new StructArray from the provided parts without validation

Safety

Safe if Self::new would not panic with the given arguments

pub fn new_empty_fields(len: usize, nulls: Option<NullBuffer>) -> Self

Create a new StructArray containing no fields

Panics

If len != nulls.len()

pub fn into_parts(self) -> (Fields, Vec<ArrayRef>, Option<NullBuffer>)

Deconstruct this array into its constituent parts

pub fn column(&self, pos: usize) -> &ArrayRef

Returns the field at pos.

pub fn num_columns(&self) -> usize

Return the number of fields in this struct array

pub fn columns(&self) -> &[ArrayRef]

Returns the fields of the struct array

pub fn column_names(&self) -> Vec<&str>

Return field names in this struct array

pub fn fields(&self) -> &Fields

Returns the [Fields] of this StructArray

pub fn column_by_name(&self, column_name: &str) -> Option<&ArrayRef>

Return child array whose field name equals to column_name

Note: A schema can currently have duplicate field names, in which case the first field will always be selected. This issue will be addressed in ARROW-11178

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

Returns a zero-copy slice of this array with the indicated offset and length.

Trait Implementations

impl Array for StructArray

fn as_any(&self) -> &dyn Any

Returns the array as Any so that it can be downcasted to a specific implementation.

fn to_data(&self) -> ArrayData

Returns the underlying data of this array

fn into_data(self) -> ArrayData

Returns the underlying data of this array

fn data_type(&self) -> &DataType

Returns a reference to the [DataType] of this array.

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

Returns a zero-copy slice of this array with the indicated offset and length.

fn len(&self) -> usize

Returns the length (i.e., number of elements) of this array.

fn is_empty(&self) -> bool

Returns whether this array is empty.

fn shrink_to_fit(&mut self)

Shrinks the capacity of any exclusively owned buffer as much as possible

fn offset(&self) -> usize

Returns the offset into the underlying data used by this array(-slice). Note that the underlying data can be shared by many arrays. This defaults to 0.

fn nulls(&self) -> Option<&NullBuffer>

Returns the null buffer of this array if any.

fn logical_null_count(&self) -> usize

Returns the total number of logical null values in this array.

fn get_buffer_memory_size(&self) -> usize

Returns the total number of bytes of memory pointed to by this array. The buffers store bytes in the Arrow memory format, and include the data as well as the validity map. Note that this does not always correspond to the exact memory usage of an array, since multiple arrays can share the same buffers or slices thereof.

fn get_array_memory_size(&self) -> usize

Returns the total number of bytes of memory occupied physically by this array. This value will always be greater than returned by get_buffer_memory_size() and includes the overhead of the data structures that contain the pointers to the various buffers.

fn logical_nulls(&self) -> Option<NullBuffer>

Returns a potentially computed [NullBuffer] that represents the logical null values of this array, if any.

fn is_null(&self, index: usize) -> bool

Returns whether the element at index is null according to Array::nulls

fn is_valid(&self, index: usize) -> bool

Returns whether the element at index is not null, the opposite of Self::is_null.

fn null_count(&self) -> usize

Returns the total number of physical null values in this array.

fn is_nullable(&self) -> bool

Returns false if the array is guaranteed to not contain any logical nulls

impl Clone for StructArray

fn clone(&self) -> StructArray

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for StructArray

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

Formats the value using the given formatter.

impl From<&StructArray> for RecordBatch

fn from(struct_array: &StructArray) -> Self

Converts to this type from the input type.

impl From<(Vec<(Arc<Field>, Arc<dyn Array>)>, Buffer)> for StructArray

fn from(pair: (Vec<(FieldRef, ArrayRef)>, Buffer)) -> Self

Converts to this type from the input type.

impl From<ArrayData> for StructArray

fn from(data: ArrayData) -> Self

Converts to this type from the input type.

impl From<RecordBatch> for StructArray

fn from(value: RecordBatch) -> Self

Converts to this type from the input type.

impl From<StructArray> for ArrayData

fn from(array: StructArray) -> Self

Converts to this type from the input type.

impl From<StructArray> for RecordBatch

fn from(value: StructArray) -> Self

Converts to this type from the input type.

impl From<Vec<(Arc<Field>, Arc<dyn Array>)>> for StructArray

fn from(v: Vec<(FieldRef, ArrayRef)>) -> Self

Converts to this type from the input type.

impl Index<&str> for StructArray

fn index(&self, name: &str) -> &Self::Output

Get a reference to a column’s array by name.

Note: A schema can currently have duplicate field names, in which case the first field will always be selected. This issue will be addressed in ARROW-11178

Panics

Panics if the name is not in the schema.

type Output = Arc<dyn Array>

The returned type after indexing.

impl PartialEq for StructArray

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl TryFrom<Vec<(&str, Arc<dyn Array>)>> for StructArray

fn try_from(values: Vec<(&str, ArrayRef)>) -> Result<Self, ArrowError>

builds a StructArray from a vector of names and arrays.

type Error = ArrowError

The type returned in the event of a conversion error.