Enum Retention 

pub enum Retention {
    CalendarYears(u32),
    Rolling(Duration),
}

When personal metering values stop being personal.

Two shapes, because § 60 Abs. 6 MsbG has two triggers and only one of them is a clock. The Messstellenbetreiber must erase or anonymise personenbezogene Messwerte as soon as storing them is no longer necessary, “spätestens jedoch nach drei Jahren ab dem Schluss des Kalenderjahres, in dem der jeweilige Messwert erhoben wurde”. Three years is the ceiling; the operative trigger is earlier and is a business decision.

A policy turns an instant into the cutoff a sweep applies to the latest reading each subject explains — see MeterCatalog::anonymise_before.

Variants

CalendarYears(u32)

The statutory shape: years full calendar years after the end of the one a value was collected in.

Not now - years, which is the tempting spelling and is wrong by up to a year in the direction that erases data still within its period. The deadline for a value collected on 2 January 2025 is 31 December 2028, not 2 January 2028, because the clock starts at the Schluss des Kalenderjahres. The year is Berlin’s, because the statute is.

Rolling(Duration)

A rolling window — the earlier “no longer necessary” trigger, where a deployment has decided what that means.

Implementations

impl Retention

pub fn cutoff(self, now: OffsetDateTime) -> OffsetDateTime

The instant a sweep run at now treats as the ceiling: a subject is due once every reading it explains starts strictly before this.

use meterstore::Retention;
use time::macros::datetime;

// Values collected in 2024 come due at the end of 2027, so a sweep any
// time in 2028 covers them — and leaves 2025's alone until 2029.
let cutoff = Retention::CalendarYears(3).cutoff(datetime!(2028-06-01 00:00 UTC));
assert_eq!(cutoff, datetime!(2024-12-31 23:00 UTC)); // 2025-01-01 Berlin

Both arms saturate towards nothing is due

A period wider than the calendar can express means “keep everything”. The other reading — subtract nothing, so the cutoff is this year — makes every subject in the store due at once, and erasure has no undo.

use meterstore::Retention;
use time::macros::datetime;

let now = datetime!(2028-06-01 00:00 UTC);
// A period nothing can be older than: nothing comes due.
assert!(Retention::CalendarYears(u32::MAX).cutoff(now) < datetime!(1970-01-01 00:00 UTC));
assert!(Retention::Rolling(time::Duration::MAX).cutoff(now) < now);

Trait Implementations

impl Clone for Retention

fn clone(&self) -> Retention

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Retention

impl Debug for Retention

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

Formats the value using the given formatter.

impl Eq for Retention

impl PartialEq for Retention

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Retention