Struct StringDictionary 

pub struct StringDictionary { /* private fields */ }

A dictionary-encoded string column.

Implementations

impl StringDictionary

pub fn new() -> Self

Create a new empty dictionary.

pub fn encode(strings: &[Option<&str>]) -> (Self, Vec<u32>)

Encode a batch of strings, returning (dictionary, encoded_ids).

The dictionary contains unique strings. encoded_ids is a Vec<u32> where each entry is the dictionary ID for the corresponding input string. Unknown/NULL strings get ID u32::MAX.

pub fn intern(&mut self, s: &str) -> u32

Insert a single string and return its ID.

pub fn lookup(&self, id: u32) -> Option<&str>

Look up a string by ID. Returns None if ID is out of range.

pub fn lookup_id(&self, s: &str) -> Option<u32>

Look up a string value and return its ID. Returns None if not found.

pub fn len(&self) -> usize

Return the number of unique strings in the dictionary.

pub fn is_empty(&self) -> bool

Check if the dictionary is empty.

pub fn serialize(&self) -> Vec<u8>

Serialize the dictionary to bytes.

Format: [num_strings: u32][for each string: [len: u32][bytes...]]

pub fn deserialize(data: &[u8]) -> Result<Self>

Deserialize a dictionary from bytes.

pub fn memory_usage(&self) -> usize

Compute the memory usage in bytes.

String bytes are counted once: the Rc<str> in strings and the map key share a single heap allocation, so the reverse-lookup keys add only the Rc pointer/refcount overhead, not a second copy of the data.

Trait Implementations

impl Clone for StringDictionary

fn clone(&self) -> StringDictionary

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for StringDictionary

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

Formats the value using the given formatter.

impl Default for StringDictionary

fn default() -> Self

Returns the “default value” for a type.