Namespace Akka.Persistence.Query

Classes

EventEnvelope

Event wrapper adding meta data for the events in the result stream of IEventsByTagQuery query, or similar queries.

The Timestamp is the time the event was stored, in ticks. The value of this property represents the number of 100-nanosecond intervals that have elapsed since 12:00:00 midnight, January 1, 0001 in the Gregorian calendar (same as `DateTime.Now.Ticks`).

FromEnd

Corresponds to a relative offset that begins the query at the Count-th event from the end of history (inclusive), e.g. "give me the last 10 events" for a tag or across all events.

Unlike Sequence and TimeBasedUuid, FromEnd is a query input only: it is never returned in an EventEnvelope. Each EventEnvelope still carries a concrete Sequence offset, so to resume a stream at a later point you use that absolute offset, not a FromEnd value. Because it is relative rather than absolute, FromEnd is not orderable and CompareTo(Offset) always throws.

The from-the-end position is resolved to a concrete start offset when the query is materialized, by reading how many matching events exist at that moment. For a live query (or any backend that resolves the count and reads the events in separate steps) this is best-effort: events written between resolving the count and reading the first batch may widen the initial window beyond Count.

Not all read journals support this offset type. Implementations that cannot honor it will throw when it is supplied, the same way they reject any other unsupported offset type.

NoOffset

Used when retrieving all events.

Offset

Used in IEventsByTagQuery implementations to signal to Akka.Persistence.Query where to begin and end event by tag queries.

For concrete implementations, see Sequence(long), NoOffset() and FromEnd.

PersistenceQuery

PersistenceQueryExtensions

PersistenceQueryProvider

Sequence

Corresponds to an ordered sequence number for the events.Note that the corresponding offset of each event is provided in the EventEnvelope, which makes it possible to resume the stream at a later point from a given offset.

The `offset` is exclusive, i.e.the event with the exact same sequence number will not be included in the returned stream. This means that you can use the offset that is returned in EventEnvelope as the `offset` parameter in a subsequent query.

TimeBasedUuid

Corresponds to an ordered unique identifier of the events. Note that the corresponding offset of each event is provided in the EventEnvelope, which makes it possible to resume the stream at a later point from a given offset.

The `offset` is exclusive, i.e. the event with the exact same sequence number will not be included in the returned stream. This means that you can use the offset that is returned in `EventEnvelope` as the `offset` parameter in a subsequent query.