private Task <T> load <T, TId>(TId id) where T : class where TId : notnull
{
var storage = _parent.StorageFor <T>();
if (storage is IDocumentStorage <T, TId> s)
{
var handler = new LoadByIdHandler <T, TId>(s, id);
return(AddItem(handler));
}
throw new DocumentIdTypeMismatchException(storage, typeof(TId));
}
public async Task <IEventStream <TDoc> > FetchForWriting(DocumentSessionBase session, TId id, long expectedStartingVersion, CancellationToken cancellation = default)
{
await _identityStrategy.EnsureAggregateStorageExists <TDoc>(session, cancellation).ConfigureAwait(false);
await session.Database.EnsureStorageExistsAsync(typeof(TDoc), cancellation).ConfigureAwait(false);
var command = _identityStrategy.BuildCommandForReadingVersionForStream(id, false);
var builder = new CommandBuilder(command);
builder.Append(";");
var handler = new LoadByIdHandler <TDoc, TId>(_storage, id);
handler.ConfigureCommand(builder, session);
long version = 0;
try
{
using var reader = await session.ExecuteReaderAsync(builder.Compile(), cancellation).ConfigureAwait(false);
if (await reader.ReadAsync(cancellation).ConfigureAwait(false))
{
version = await reader.GetFieldValueAsync <long>(0, cancellation).ConfigureAwait(false);
}
if (expectedStartingVersion != version)
{
throw new ConcurrencyException(
$"Expected the existing version to be {expectedStartingVersion}, but was {version}",
typeof(TDoc), id);
}
await reader.NextResultAsync(cancellation).ConfigureAwait(false);
var document = await handler.HandleAsync(reader, session, cancellation).ConfigureAwait(false);
return(version == 0
? _identityStrategy.StartStream <TDoc>(document, session, id, cancellation)
: _identityStrategy.AppendToStream <TDoc>(document, session, id, version, cancellation));
}
catch (Exception e)
{
if (e.Message.Contains(MartenCommandException.MaybeLockedRowsMessage))
{
throw new StreamLockedException(id, e.InnerException);
}
throw;
}
}
