Interface IHaveKnownChanges

Namespace

Cratis.Arc.Queries

Assembly

Cratis.Arc.Core.dll

Defines a collection emitted by an observable query that already knows which of its items changed.

public interface IHaveKnownChanges

Extension Methods

MethodCalls.CallGenericMethod<TOut, T>(T, Expression<Func<T, Func<TOut>>>, params Type[])

MethodCalls.CallGenericMethod<TOut, T, T1>(T, Expression<Func<T, Func<T1, TOut>>>, T1, params Type[])

MethodCalls.CallGenericMethod<TOut, T, T1, T2>(T, Expression<Func<T, Func<T1, T2, TOut>>>, T1, T2, params Type[])

MethodCalls.CallGenericMethod<TOut, T, T1, T2, T3>(T, Expression<Func<T, Func<T1, T2, T3, TOut>>>, T1, T2, T3, params Type[])

ConverterExtensions.ConvertTo(object, Type)

ConceptExtensions.GetConceptValue(object)

ConceptExtensions.IsConcept(object)

JsonValueExtensions.ToJsonValue(object?)

ObservableExtensions.InvokeAndWrapWithSubject<TResult>(object, Func<CancellationToken, IObservable<TResult>>)

ObservableExtensions.InvokeAndWrapWithTransformSubject<TResult, TSource>(object, Func<CancellationToken, IObservable<TSource>>, Func<TSource, TResult>)

Remarks

An observable query provider that watches a data source - a MongoDB change stream, for example - is told exactly which document changed. Without a way to pass that on, the emission is just a new snapshot and the delta has to be rediscovered downstream by comparing every item of the new snapshot against every item of the previous one, which costs time proportional to the size of the collection for a change that touched a single row.

An emitted collection implementing this states its own delta instead. The interface is deliberately additive: the emitted value is still an IEnumerable<T> of the read model, so a subscriber that does not know about this sees no difference, and a provider that cannot know what changed simply does not implement it and is served by the comparison fallback.

Properties

Changes

Gets the changes this emission represents, or null when the emission is a whole snapshot rather than a delta - the initial query result, or a re-read after reconnecting.

IReadOnlyList<CollectionChange>? Changes { get; }

Property Value

IReadOnlyList<CollectionChange>