Add incr restore change sender (#9603)

Author: Enjection

ydb/core/change_exchange/change_sender.cpp

@@ -10,6 +10,7 @@
 namespace NKikimr::NChangeExchange {
 
 void TChangeSender::LazyCreateSender(THashMap<ui64, TSender>& senders, ui64 partitionId) {
+    ++UninitSenders;
     auto res = senders.emplace(partitionId, TSender{});
     Y_ABORT_UNLESS(res.second);
 
@@ -27,6 +28,7 @@ void TChangeSender::RegisterSender(ui64 partitionId) {
 
     Y_ABORT_UNLESS(!sender.ActorId);
     sender.ActorId = ActorOps->RegisterWithSameMailbox(SenderFactory->CreateSender(partitionId));
+    --UninitSenders;
 }
 
 void TChangeSender::CreateMissingSenders(const TVector<ui64>& partitionIds) {

ydb/core/change_exchange/change_sender.h

@@ -174,6 +174,10 @@ class TChangeSender {
         return ReadySenders == Senders.size();
     }
 
+    inline bool IsAllSendersReadyOrUninit() {
+        return ReadySenders + UninitSenders == Senders.size();
+    }
+
     void SetPartitionResolver(IPartitionResolverVisitor* partitionResolver) {
         PartitionResolver.Reset(partitionResolver);
     }
@@ -194,6 +198,7 @@ class TChangeSender {
 
     THashMap<ui64, TSender> Senders; // ui64 is partition id
     ui64 ReadySenders = 0;
+    ui64 UninitSenders = 0;
     TSet<TEnqueuedRecord> Enqueued;
     TSet<TIncompleteRecord> PendingBody;
     TMap<ui64, IChangeRecord::TPtr> PendingSent; // ui64 is order

ydb/core/tx/datashard/change_exchange_impl.h

@@ -8,6 +8,7 @@ namespace NDataShard {
 
 IActor* CreateAsyncIndexChangeSender(const TDataShardId& dataShard, const TTableId& userTableId, const TPathId& indexPathId);
 IActor* CreateCdcStreamChangeSender(const TDataShardId& dataShard, const TPathId& streamPathId);
+IActor* CreateIncrRestoreChangeSender(const TActorId& changeServerActor, const TDataShardId& dataShard, const TTableId& userTableId, const TPathId& restoreTargetPathId);
 
 } // NDataShard
 } // NKikimr