Enum CadencePolicy 

#[non_exhaustive]
pub enum CadencePolicy {
    Default,
    Disabled,
    Every(SnapshotCadence),
}

What the snapshot cadence should do, for Tuning::cadence.

Why this is not Option<SnapshotCadence>

Database::open_with_cadence takes Option<SnapshotCadence>, where None means no cadence at all. Carrying that field into Tuning unchanged would have made it the one field in the struct whose None is a request to change the behaviour rather than a request to leave it alone — and since Tuning derives Default, open_tuned(path, Tuning::default()) would then have silently disabled snapshots, while open(path) runs them. Two calls that read as synonyms, one of which stops writing anchors.

So the tri-state is written out. Default is the default cadence, matching Database::open; Disabled is open_with_cadence(path, None), and has to be asked for by name.

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.

Default

SnapshotCadence::default, as Database::open uses.

Disabled

No cadence task. close() is then the only thing that writes an anchor (§5.5, D-053).

Every(SnapshotCadence)

An explicit cadence.

Trait Implementations

impl Clone for CadencePolicy

fn clone(&self) -> CadencePolicy

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for CadencePolicy

impl Debug for CadencePolicy

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

Formats the value using the given formatter.

impl Default for CadencePolicy

fn default() -> CadencePolicy

Returns the “default value” for a type.

impl Eq for CadencePolicy

impl PartialEq for CadencePolicy

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for CadencePolicy