Enum LockKind

pub enum LockKind {
    None,
    Shared,
    Reserved,
    Pending,
    Exclusive,
}

The access an object is opened with.

Variants

None

No locks are held. The database may be neither read nor written. Any internally cached data is considered suspect and subject to verification against the database file before being used. Other processes can read or write the database as their own locking states permit. This is the default state.

Shared

The database may be read but not written. Any number of processes can hold LockKind::Shared locks at the same time, hence there can be many simultaneous readers. But no other thread or process is allowed to write to the database file while one or more LockKind::Shared locks are active.

Reserved

A LockKind::Reserved lock means that the process is planning on writing to the database file at some point in the future but that it is currently just reading from the file. Only a single LockKind::Reserved lock may be active at one time, though multiple LockKind::Shared locks can coexist with a single LockKind::Reserved lock. LockKind::Reserved differs from LockKind::Pending in that new LockKind::Shared locks can be acquired while there is a LockKind::Reserved lock.

Pending

A LockKind::Pending lock means that the process holding the lock wants to write to the database as soon as possible and is just waiting on all current LockKind::Shared locks to clear so that it can get an LockKind::Exclusive lock. No new LockKind::Shared locks are permitted against the database if a LockKind::Pending lock is active, though existing LockKind::Shared locks are allowed to continue.

Exclusive

An LockKind::Exclusive lock is needed in order to write to the database file. Only one LockKind::Exclusive lock is allowed on the file and no other locks of any kind are allowed to coexist with an LockKind::Exclusive lock. In order to maximize concurrency, SQLite works to minimize the amount of time that LockKind::Exclusive locks are held.

Trait Implementations

impl Clone for LockKind

fn clone(&self) -> LockKind

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for LockKind

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

Formats the value using the given formatter.

impl Default for LockKind

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for LockKind

fn eq(&self, other: &LockKind) -> 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.

impl PartialOrd for LockKind

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

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

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

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

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

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

impl Copy for LockKind

impl Eq for LockKind

impl StructuralPartialEq for LockKind