Struct DictionaryEncoding 

pub struct DictionaryEncoding { /* private fields */ }

A dictionary-encoded string column.

Stores unique strings in a dictionary and references them by integer codes.

Implementations

impl DictionaryEncoding

pub fn new(dictionary: Arc<[Arc<str>]>, codes: Vec<u32>) -> Self

Creates a new dictionary encoding from a dictionary and codes.

pub fn with_nulls(self, null_bitmap: Vec<u64>) -> Self

Creates a dictionary encoding with a null bitmap.

pub fn len(&self) -> usize

Returns the number of values.

pub fn is_empty(&self) -> bool

Returns whether the encoding is empty.

pub fn dictionary_size(&self) -> usize

Returns the number of unique strings in the dictionary.

pub fn dictionary(&self) -> &Arc<[Arc<str>]>

Returns the dictionary.

pub fn codes(&self) -> &[u32]

Returns the encoded values.

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

Returns whether the value at index is null.

pub fn get(&self, index: usize) -> Option<&str>

Returns the string value at the given index.

Returns None if the value is null.

pub fn get_code(&self, index: usize) -> Option<u32>

Returns the code at the given index.

pub fn iter(&self) -> impl Iterator<Item = Option<&str>>

Iterates over all values, yielding Option<&str>.

pub fn compression_ratio(&self) -> f64

Returns the compression ratio (original size / compressed size).

A ratio > 1.0 means compression is effective.

pub fn encode(&self, value: &str) -> Option<u32>

Encodes a lookup value into a code, if it exists in the dictionary.

pub fn filter_by_code(&self, predicate: impl Fn(u32) -> bool) -> Vec<usize>

Filters the encoding to only include rows matching a predicate code.

Trait Implementations

impl Clone for DictionaryEncoding

fn clone(&self) -> DictionaryEncoding

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for DictionaryEncoding

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

Formats the value using the given formatter.