Struct txn_types::Key

pub struct Key(Vec<u8>);

Key type.

Keys have 2 types of binary representation - raw and encoded. The raw representation is for public interface, the encoded representation is for internal storage. We can get both representations from an instance of this type.

Orthogonal to binary representation, keys may or may not embed a timestamp, but this information is transparent to this type, the caller must use it consistently.

Implementations

impl Key

Core functions for Key.

pub fn from_raw(key: &[u8]) -> Key

Creates a key from raw bytes.

pub fn from_raw_maybe_unbounded(key: &[u8]) -> Option<Key>

Creates a key from raw bytes but returns None if the key is an empty slice.

pub fn into_raw(self) -> Result<Vec<u8>, Error>

Gets and moves the raw representation of this key.

pub fn to_raw(&self) -> Result<Vec<u8>, Error>

Gets the raw representation of this key.

pub fn from_encoded(encoded_key: Vec<u8>) -> Key

Creates a key from encoded bytes vector.

pub fn from_encoded_slice(encoded_key: &[u8]) -> Key

Creates a key with reserved capacity for timestamp from encoded bytes slice.

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

Gets the encoded representation of this key.

pub fn into_encoded(self) -> Vec<u8>

Gets and moves the encoded representation of this key.

pub fn append_ts(self, ts: TimeStamp) -> Key

Creates a new key by appending a u64 timestamp to this key.

pub fn decode_ts(&self) -> Result<TimeStamp, Error>

Gets the timestamp contained in this key.

Preconditions: the caller must ensure this is actually a timestamped key.

pub fn truncate_ts(self) -> Result<Key, Error>

Creates a new key by truncating the timestamp from this key.

Preconditions: the caller must ensure this is actually a timestamped key.

pub fn split_on_ts_for(key: &[u8]) -> Result<(&[u8], TimeStamp), Error>

Split a ts encoded key, return the user key and timestamp.

pub fn truncate_ts_for(key: &[u8]) -> Result<&[u8], Error>

Extract the user key from a ts encoded key.

pub fn decode_ts_from(key: &[u8]) -> Result<TimeStamp, Error>

Decode the timestamp from a ts encoded key.

pub fn is_user_key_eq(ts_encoded_key: &[u8], user_key: &[u8]) -> bool

Whether the user key part of a ts encoded key ts_encoded_key equals to the encoded user key user_key.

There is an optimization in this function, which is to compare the last 8 encoded bytes first before comparing the rest. It is because in TiDB many records are ended with an 8 byte row id and in many situations only this part is different when calling this function.

pub fn is_encoded_from(&self, raw_key: &[u8]) -> bool

Returns whether the encoded key is encoded from raw_key.

pub fn gen_hash(&self) -> u64

TiDB uses the same hash algorithm.

Trait Implementations

impl Clone for Key

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Key

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

Formats the value using the given formatter.

impl Display for Key

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

Formats the value using the given formatter.

impl Eq for Key

impl Hash for Key

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

pub fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given Hasher.

impl Ord for Key

fn cmp(&self, other: &Key) -> Ordering

This method returns an Ordering between self and other.

#[must_use]pub fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

#[must_use]pub fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

#[must_use]pub fn clamp(self, min: Self, max: Self) -> Self

Restrict a value to a certain interval.

impl PartialEq<Key> for Key

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

This method tests for self and other values to be equal, and is used by ==.

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

This method tests for !=.

impl PartialOrd<Key> for Key

fn partial_cmp(&self, other: &Key) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use]pub fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use]pub fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use]pub fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use]pub fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl StructuralEq for Key

impl StructuralPartialEq for Key