Merge 7e32c10 into bd5ea97

Author: ijon

ydb/core/tx/schemeshard/schemeshard__operation_memory_changes.cpp

@@ -47,7 +47,13 @@ void TMemoryChanges::GrabShard(TSchemeShard *ss, const TShardIdx &shardId) {
 }
 
 void TMemoryChanges::GrabDomain(TSchemeShard* ss, const TPathId& pathId) {
-    Grab<TSubDomainInfo>(pathId, ss->SubDomains, SubDomains);
+    // Copy TSubDomainInfo from ss->SubDomains to local SubDomains.
+    // Make sure that copy will be made only when needed.
+    const auto found = ss->SubDomains.find(pathId);
+    Y_ABORT_UNLESS(found != ss->SubDomains.end());
+    if (!SubDomains.contains(pathId)) {
+        SubDomains.emplace(pathId, MakeIntrusive<TSubDomainInfo>(*found->second));
+    }
 }
 
 void TMemoryChanges::GrabNewIndex(TSchemeShard* ss, const TPathId& pathId) {
@@ -178,15 +184,12 @@ void TMemoryChanges::UnDo(TSchemeShard* ss) {
         Shards.pop();
     }
 
-    while (SubDomains) {
-        const auto& [id, elem] = SubDomains.top();
-        if (elem) {
-            ss->SubDomains[id] = elem;
-        } else {
-            ss->SubDomains.erase(id);
-        }
-        SubDomains.pop();
+    // Restore ss->SubDomains entries to saved copies of TSubDomainInfo objects.
+    // No copy, simple pointer replacement.
+    for (const auto& [id, elem] : SubDomains) {
+        ss->SubDomains[id] = elem;
     }
+    SubDomains.clear();
 
     while (TxStates) {
         const auto& [id, elem] = TxStates.top();

ydb/core/tx/schemeshard/schemeshard__operation_memory_changes.h

@@ -33,8 +33,12 @@ class TMemoryChanges: public TSimpleRefCount<TMemoryChanges> {
     using TShardState = std::pair<TShardIdx, THolder<TShardInfo>>;
     TStack<TShardState> Shards;
 
-    using TSubDomainState = std::pair<TPathId, TSubDomainInfo::TPtr>;
-    TStack<TSubDomainState> SubDomains;
+    // Actually, any single subdomain should not be grabbed at more than one version
+    // per transaction/operation.
+    // And transaction/operation could not work on more than one subdomain.
+    // But just to be on the safe side (migrated paths, anyone?) we allow several
+    // subdomains to be grabbed.
+    THashMap<TPathId, TSubDomainInfo::TPtr> SubDomains;
 
     using TTxState = std::pair<TOperationId, THolder<TTxState>>;
     TStack<TTxState> TxStates;
@@ -78,7 +82,7 @@ class TMemoryChanges: public TSimpleRefCount<TMemoryChanges> {
     void GrabExternalTable(TSchemeShard* ss, const TPathId& pathId);
 
     void GrabExternalDataSource(TSchemeShard* ss, const TPathId& pathId);
-    
+
     void GrabNewView(TSchemeShard* ss, const TPathId& pathId);
     void GrabView(TSchemeShard* ss, const TPathId& pathId);