Struct MapArray 

pub struct MapArray {
    data_type: DataType,
    nulls: Option<NullBuffer>,
    entries: StructArray,
    value_offsets: OffsetBuffer<i32>,
}

An array of key-value maps

Keys should always be non-null, but values can be null.

MapArray is physically a ListArray of key values pairs stored as an entries StructArray with 2 child fields.

See also

• MapBuilder for how to construct a MapArray
• Self::from_vec_of_maps for ergonomically creating maps for testing

Fields

data_type: DataType

nulls: Option<NullBuffer>

entries: StructArray

The StructArray that is the direct child of this array

value_offsets: OffsetBuffer<i32>

The start and end offsets of each entry

Implementations

impl MapArray

pub fn try_new( field: FieldRef, offsets: OffsetBuffer<i32>, entries: StructArray, nulls: Option<NullBuffer>, ordered: bool, ) -> Result<Self, ArrowError>

Create a new MapArray from the provided parts

See MapBuilder for a higher-level interface to construct a MapArray

Errors

Errors if

• offsets.len() - 1 != nulls.len()
• offsets.last() > entries.len()
• field.is_nullable()
• entries.null_count() != 0
• entries.columns().len() != 2
• field.data_type() != entries.data_type()

pub fn new( field: FieldRef, offsets: OffsetBuffer<i32>, entries: StructArray, nulls: Option<NullBuffer>, ordered: bool, ) -> Self

Create a new MapArray from the provided parts

See MapBuilder for a higher-level interface to construct a MapArray

Panics

Panics if Self::try_new returns an error

pub fn into_parts( self, ) -> (FieldRef, OffsetBuffer<i32>, StructArray, Option<NullBuffer>, bool)

Deconstruct this array into its constituent parts

pub fn offsets(&self) -> &OffsetBuffer<i32>

Returns a reference to the offsets of this map

Unlike Self::value_offsets this returns the [OffsetBuffer] allowing for zero-copy cloning

pub fn keys(&self) -> &ArrayRef

Returns a reference to the keys of this map

pub fn values(&self) -> &ArrayRef

Returns a reference to the values of this map

pub fn entries(&self) -> &StructArray

Returns a reference to the StructArray entries of this map

pub fn entries_fields(&self) -> (&Field, &Field)

Returns a reference to the fields of the StructArray that backs this map.

pub fn key_type(&self) -> &DataType

Returns the data type of the map’s keys.

pub fn value_type(&self) -> &DataType

Returns the data type of the map’s values.

pub unsafe fn value_unchecked(&self, i: usize) -> StructArray

Returns ith value of this map array.

Note: This method does not check for nulls and the value is arbitrary if is_null returns true for the index.

Safety

Caller must ensure that the index is within the array bounds

pub fn value(&self, i: usize) -> StructArray

Returns ith value of this map array.

This is a StructArray containing two fields

Note: This method does not check for nulls and the value is arbitrary (but still well-defined) if is_null returns true for the index.

Panics

Panics if index i is out of bounds

pub fn value_offsets(&self) -> &[i32]

Returns the offset values in the offsets buffer

pub fn value_length(&self, i: usize) -> i32

Returns the length for value at index i.

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

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

pub fn iter(&self) -> MapArrayIter<'_>

constructs a new iterator

impl MapArray

fn try_new_from_array_data(data: ArrayData) -> Result<Self, ArrowError>

pub fn new_from_strings<'a>( keys: impl Iterator<Item = &'a str>, values: &dyn Array, entry_offsets: &[u32], ) -> Result<Self, ArrowError>

Creates map array from provided keys, values and entry_offsets.

pub fn from_vec_of_maps<KeyArray, ValueArray, K, V>( input: Vec<Option<Vec<(K, Option<V>)>>>, ordered: bool, ) -> Self

where KeyArray: Array + 'static, ValueArray: Array + 'static, Vec<K>: Into<KeyArray>, Vec<Option<V>>: Into<ValueArray>,

Helper to create MapArray from Vecs of entries so the code will look clean and straightforward

the input is: Vec<Option<Map>> where each Map is Vec<(Key, Option<Value>)>

Useful for tests, this should not be used for performance sensitive operations

use std::collections::HashMap;

let map = vec![
   // {}
   Some(vec![]),
   // null
   None,
   // { "a": 1, "b": null, "cd": 4 }
   Some(vec![
       ("a", Some(1)),
       ("b", None),
       ("cd", Some(4)),
   ]),
   // { "e": 0 }
   Some(vec![("e", Some(0))]),
];
let ordered = true;

// created map: [{}, null, {"a": 1, "b": null, "cd": 4}, {"e": 0}]
let map_array = MapArray::from_vec_of_maps::<StringArray, Int32Array, _, _>(map, ordered);
// Or you could fill the last 2 generics manually for the key array item and value array item
// let map_array = MapArray::from_vec_of_maps::<StringArray, Int32Array, &str, i32>(map, ordered);

Trait Implementations

impl Array for MapArray

SAFETY: Correctly implements the contract of Arrow Arrays

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 claim(&self, pool: &dyn MemoryPool)

Claim memory used by this array in the provided memory pool.

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 ArrayAccessor for &MapArray

type Item = StructArray

The Arrow type of the element being accessed.

fn value(&self, index: usize) -> Self::Item

Returns the element at index i

unsafe fn value_unchecked(&self, index: usize) -> Self::Item

Returns the element at index i

impl Clone for MapArray

fn clone(&self) -> MapArray

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for MapArray

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

Formats the value using the given formatter.

impl From<ArrayData> for MapArray

fn from(data: ArrayData) -> Self

Converts to this type from the input type.

impl From<MapArray> for ArrayData

fn from(array: MapArray) -> Self

Converts to this type from the input type.

impl From<MapArray> for ListArray

fn from(value: MapArray) -> Self

Converts to this type from the input type.

impl PartialEq for MapArray

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.