Struct fdb::KeySelector

pub struct KeySelector { /* private fields */ }

KeySelector identifies a particular key in the database.

FDB’s lexicographically ordered data model permits finding keys based on their order (for example, finding the first key in the database greater than a given key). Key selectors represent a description of a key in the database that could be resolved to an actual key by transaction’s get_key or used directly as the beginning or end of a range in transaction’s get_range.

For more about how key selectors work in practice, see the key selector documentation. Note that the way key selectors are resolved is somewhat non-intuitive, so users who wish to use a key selector other than the default ones described below should probably consult that documentation before proceeding.

Generally one of the following methods should be used to construct a KeySelector.

• last_less_than
• last_less_or_equal
• first_greater_than
• first_greater_or_equal

This is an immutable type. The add(i32) call does not modify internal state, but returns a new value.

Implementations

impl KeySelector

pub fn new(key: impl Into<Key>, or_equal: bool, offset: i32) -> KeySelector

Create a new KeySelector from the given parameters.

pub fn add(self, offset: i32) -> KeySelector

Returns a new KeySelector offset by a given number of keys from this one.

pub fn first_greater_or_equal(key: impl Into<Key>) -> KeySelector

Creates a KeySelector that picks the first key greater than or equal to the parameter.

pub fn first_greater_than(key: impl Into<Key>) -> KeySelector

Creates a KeySelector that picks the first key greater than or equal to the parameter.

pub fn get_key(&self) -> &Key

Returns a reference to the key that serves as the anchor for this KeySelector.

pub fn get_offset(&self) -> i32

Returns the key offset parameter for this KeySelector.

pub fn last_less_or_equal(key: impl Into<Key>) -> KeySelector

Creates a KeySelector that picks the last key less than or equal to the parameter.

pub fn last_less_than(key: impl Into<Key>) -> KeySelector

Creates a KeySelector that picks the last key less than the parameter.

Trait Implementations

impl Clone for KeySelector

fn clone(&self) -> KeySelector

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for KeySelector

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

Formats the value using the given formatter.