Add mutex to tryGetTable only for materialized table (not nested)

src/Databases/PostgreSQL/DatabaseMaterializePostgreSQL.cpp

@@ -122,6 +122,8 @@ StoragePtr DatabaseMaterializePostgreSQL::tryGetTable(const String & name, const
         }
     }
 
+    /// Note: In select query we call MaterializePostgreSQL table and it calls tryGetTable from its nested.
+    std::lock_guard lock(tables_mutex);
     auto table = materialized_tables.find(name);
     /// Here it is possible that nested table is temporarily out of reach, but return storage anyway,
     /// it will not allow to read if nested is unavailable at the moment

src/Databases/PostgreSQL/DatabaseMaterializePostgreSQL.h

@@ -66,6 +66,7 @@ private:
 
     std::shared_ptr<PostgreSQLReplicationHandler> replication_handler;
     std::map<std::string, StoragePtr> materialized_tables;
+    mutable std::mutex tables_mutex;
 };
 
 }