Struct actyxos_sdk::event::OffsetMap

pub struct OffsetMap(_);

Multi-dimensional cursor for event streams: an OffsetMap describes the set of events given by the event streams of each included source up to the associated Offset.

All stream delivery modes supported by the Event Service respect the order of offsets of the events published by each single ActyxOS node. This order is consistent with the Lamport timestamp order because both numbers are assigned to published events in strictly monotonically increasing fashion, i.e. greater Offset implies greater Lamport timestamp and vice versa.

Note that if the OffsetMap contains offset 42 for SourceID "abc" it denotes that events with offsets 0 through 42 (inclusive) are included within the OffsetMap.

A common usage pattern is to store the OffsetMap describing the events already consumed from an event stream together with the computation results from processing those events (preferably within the same database transaction, if applicable). When restarting the process, this OffsetMap can be read and the stream can be resumed from where the process left off previously.

Arithmetics

OffsetMap has a partial order: when the set of events described by one is a strict subset of the set of events described by another, then one is said to be smaller than the other. It may be that one OffsetMap contains events that the other does not and vice versa, in which case they are incomparable (partial_cmp will return None).

An event may be added into an OffsetMap to denote that from the event’s source all events up to this one shall be included in the OffsetMap.

let mut offsets: OffsetMap = OffsetMap::empty();
let event: Event<Payload> = Event::mk_test("semantics", "name", "42").unwrap();

// keeping track of having seen this event:
offsets += &event;
assert!(offsets.contains(&event));

The difference of two offset maps yields the number of events contained within the first but not within the second one (i.e. it counts the size of the difference set).

Implementations

impl OffsetMap

pub fn empty() -> Self

The empty OffsetMap is equivalent to the beginning of time, it does not contain any event.

pub fn contains<T>(&self, event: &Event<T>) -> bool

Check whether the given Event’s offset and source ID are contained within this OffsetMap.

pub fn size(&self) -> u64

Counts the number of offsets spanned by this OffsetMap.

pub fn union_with<'a>(&'a mut self, other: &OffsetMap) -> &'a mut Self

Merge the other OffsetMap into this one, taking the union of their event sets.

pub fn union(&self, other: &OffsetMap) -> OffsetMap

Compute the union of two sets of events described by OffsetMaps

pub fn intersection(&self, other: &OffsetMap) -> OffsetMap

Compute the intersection of two sets of events described by OffsetMaps

pub fn into_inner(self) -> HashMap<SourceId, Offset>

Trait Implementations

impl<'_, T> AddAssign<&'_ Event<T>> for OffsetMap

fn add_assign(&mut self, other: &Event<T>)

Performs the += operation.

impl AsRef<HashMap<SourceId, Offset, RandomState>> for OffsetMap

fn as_ref(&self) -> &HashMap<SourceId, Offset>

Performs the conversion.

impl<'_> BitAnd<&'_ OffsetMap> for &'_ OffsetMap

type Output = OffsetMap

The resulting type after applying the & operator.

fn bitand(self, rhs: Self) -> Self::Output

Performs the & operation.

impl BitAnd<OffsetMap> for OffsetMap

type Output = OffsetMap

The resulting type after applying the & operator.

fn bitand(self, rhs: Self) -> Self::Output

Performs the & operation.

impl BitAndAssign<OffsetMap> for OffsetMap

fn bitand_assign(&mut self, rhs: Self)

Performs the &= operation.

impl<'_> BitOr<&'_ OffsetMap> for &'_ OffsetMap

type Output = OffsetMap

The resulting type after applying the | operator.

fn bitor(self, rhs: Self) -> Self::Output

Performs the | operation.

impl BitOr<OffsetMap> for OffsetMap

type Output = OffsetMap

The resulting type after applying the | operator.

fn bitor(self, rhs: Self) -> Self::Output

Performs the | operation.

impl BitOrAssign<OffsetMap> for OffsetMap

fn bitor_assign(&mut self, rhs: Self)

Performs the |= operation.

impl Clone for OffsetMap

fn clone(&self) -> OffsetMap

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for OffsetMap

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

Formats the value using the given formatter.

impl Default for OffsetMap

fn default() -> Self

Returns the "default value" for a type.

impl<'de> Deserialize<'de> for OffsetMap

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error> where
    __D: Deserializer<'de>, 

Deserialize this value from the given Serde deserializer.

impl Eq for OffsetMap

impl From<HashMap<SourceId, Offset, RandomState>> for OffsetMap

fn from(map: HashMap<SourceId, Offset>) -> Self

Performs the conversion.

impl PartialEq<OffsetMap> for OffsetMap

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

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

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

This method tests for !=.

impl PartialOrd<OffsetMap> for OffsetMap

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

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

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

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

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

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

#[must_use]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 Serialize for OffsetMap

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

Serialize this value into the given Serde serializer.

impl StructuralEq for OffsetMap

impl StructuralPartialEq for OffsetMap

impl<'_, '_> Sub<&'_ OffsetMap> for &'_ OffsetMap

type Output = u64

The resulting type after applying the - operator.

fn sub(self, other: &OffsetMap) -> u64

Performs the - operation.

impl Sub<OffsetMap> for OffsetMap

type Output = u64

The resulting type after applying the - operator.

fn sub(self, other: Self) -> u64

Performs the - operation.

impl<'_, T> SubAssign<&'_ Event<T>> for OffsetMap

fn sub_assign(&mut self, other: &Event<T>)

Ensure that the given event is no longer contained within this OffsetMap.