Fix: possible race condition on EXCHANGE TABLES query

src/Interpreters/Context.cpp

@@ -906,6 +906,16 @@ String Context::getFilesystemCacheUser() const
     return shared->filesystem_cache_user;
 }
 
+StoragePtr Context::getOrCacheStorage(const String & name, std::function<StoragePtr()> f) const
+{
+    if (auto storage = storage_cache.find(name); storage != storage_cache.end())
+        return storage->second;
+    auto storage = f();
+    if (storage)
+        storage_cache.insert({name, storage});
+    return storage;
+}
+
 Strings Context::getWarnings() const
 {
     Strings common_warnings;

src/Interpreters/Context.h

@@ -33,6 +33,7 @@
 #include <memory>
 #include <mutex>
 #include <optional>
+#include <unordered_map>
 
 
 namespace Poco::Net { class IPAddress; }
@@ -424,6 +425,9 @@ class ContextData
     /// mutation tasks of one mutation executed against different parts of the same table.
     PreparedSetsCachePtr prepared_sets_cache;
 
+    /// Cache for storages resolved during query processing.
+    mutable std::unordered_map<String, StoragePtr> storage_cache;
+
 public:
     /// Some counters for current query execution.
     /// Most of them are workarounds and should be removed in the future.
@@ -518,6 +522,8 @@ class Context: public ContextData, public std::enable_shared_from_this<Context>
     String getFilesystemCachesPath() const;
     String getFilesystemCacheUser() const;
 
+    StoragePtr getOrCacheStorage(const String & name, std::function<StoragePtr()> f) const;
+
     /// A list of warnings about server configuration to place in `system.warnings` table.
     Strings getWarnings() const;
 

src/Interpreters/JoinedTables.cpp

@@ -232,7 +232,7 @@ StoragePtr JoinedTables::getLeftTableStorage()
     }
 
     /// Read from table. Even without table expression (implicit SELECT ... FROM system.one).
-    return DatabaseCatalog::instance().getTable(table_id, context);
+    return context->getQueryContext()->getOrCacheStorage(table_id.getFullNameNotQuoted(), [&](){ return DatabaseCatalog::instance().getTable(table_id, context); });
 }
 
 bool JoinedTables::resolveTables()
@@ -318,7 +318,7 @@ std::shared_ptr<TableJoin> JoinedTables::makeTableJoin(const ASTSelectQuery & se
     if (table_to_join.database_and_table_name)
     {
         auto joined_table_id = context->resolveStorageID(table_to_join.database_and_table_name);
-        StoragePtr storage = DatabaseCatalog::instance().tryGetTable(joined_table_id, context);
+        StoragePtr storage = context->getQueryContext()->getOrCacheStorage(joined_table_id.getFullNameNotQuoted(), [&](){ return DatabaseCatalog::instance().tryGetTable(joined_table_id, context); });
         if (storage)
         {
             if (auto storage_join = std::dynamic_pointer_cast<StorageJoin>(storage); storage_join)