Enum LockError 

#[non_exhaustive]
pub enum LockError {
    Conflict,
    NotHeld,
}

Reasons a lock operation can fail.

Every fallible entry point on LockManager returns Result<_, LockError>. The variants are deliberately coarse: a caller either got the lock or it did not, and the few ways “did not” can happen are distinct enough to branch on. The type is #[non_exhaustive] because later milestones (wait queues, deadlock detection) add variants such as a timeout and a deadlock-victim signal; matching code must keep a wildcard arm.

Examples

use lock_db::{LockError, LockManager, LockMode, ResourceId, TxnId};

let lm = LockManager::new();
let row = ResourceId::new(1);

// Txn 1 takes an exclusive lock.
lm.try_acquire(TxnId::new(1), row, LockMode::Exclusive).unwrap();

// Txn 2 cannot get any lock on the same row right now.
assert_eq!(lm.try_acquire(TxnId::new(2), row, LockMode::Shared), Err(LockError::Conflict));

// Releasing a lock you never held is a distinct error.
assert_eq!(lm.release(TxnId::new(9), row), Err(LockError::NotHeld));

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Conflict

The lock could not be granted without blocking.

The requested mode is incompatible with a mode another transaction already holds on the resource, or the request is an upgrade (shared to exclusive) that other shared holders are blocking. Returned by the non-blocking try_acquire; the caller decides whether to retry, wait, or abort.

NotHeld

A release named a (transaction, resource) pair that holds no lock.

Returned by release when the transaction does not currently hold a lock on the resource. This usually signals a double release or a bookkeeping bug in the caller’s transaction layer.

Trait Implementations

impl Clone for LockError

fn clone(&self) -> LockError

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for LockError

impl Debug for LockError

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for LockError

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Display for LockError

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

Formats the value using the given formatter.

impl Eq for LockError

impl Error for LockError

Available on crate feature std only.

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl Hash for LockError

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

Feeds this value into the given Hasher.

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

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for LockError

fn eq(&self, other: &LockError) -> 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 Serialize for LockError

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for LockError