diff --git a/dbms/src/Databases/DatabaseOnDisk.h b/dbms/src/Databases/DatabaseOnDisk.h
index 08a4319affb..761d55bd90b 100644
--- a/dbms/src/Databases/DatabaseOnDisk.h
+++ b/dbms/src/Databases/DatabaseOnDisk.h
@@ -18,7 +18,7 @@ namespace detail
     ASTPtr getCreateQueryFromMetadata(const String & metadata_path, const String & database, bool throw_on_error);
 }
 
-/* Class to provide basic operations with tables stored on disk.
+/* Class to provide basic operations with tables when metadata is stored on disk in .sql files.
  */
 class DatabaseOnDisk
 {
diff --git a/dbms/src/Storages/System/StorageSystemColumns.cpp b/dbms/src/Storages/System/StorageSystemColumns.cpp
index 46ad7634a8f..c1d5c827f30 100644
--- a/dbms/src/Storages/System/StorageSystemColumns.cpp
+++ b/dbms/src/Storages/System/StorageSystemColumns.cpp
@@ -264,7 +264,11 @@ BlockInputStreams StorageSystemColumns::read(
         MutableColumnPtr database_column_mut = ColumnString::create();
         for (const auto & database : databases)
         {
-            if (context.hasDatabaseAccessRights(database.first) && database.second->getEngineName() != "Lazy")
+            /// We are skipping "Lazy" database because we cannot afford initialization of all its tables.
+            /// This should be documented.
+
+            if (context.hasDatabaseAccessRights(database.first)
+                && database.second->getEngineName() != "Lazy")
                 database_column_mut->insert(database.first);
         }
 
diff --git a/dbms/src/Storages/System/StorageSystemTables.cpp b/dbms/src/Storages/System/StorageSystemTables.cpp
index 268cea76bec..27861fcb909 100644
--- a/dbms/src/Storages/System/StorageSystemTables.cpp
+++ b/dbms/src/Storages/System/StorageSystemTables.cpp
@@ -61,13 +61,15 @@ static ColumnPtr getFilteredDatabases(const ASTPtr & query, const Context & cont
     return block.getByPosition(0).column;
 }
 
-static bool needLockStructure(const DatabasePtr& database, const Block& header)
+/// Avoid heavy operation on tables if we only queried columns that we can get without table object.
+/// Otherwise it will require table initialization for Lazy database.
+static bool needLockStructure(const DatabasePtr & database, const Block & header)
 {
     if (database->getEngineName() != "Lazy")
         return true;
 
     static const std::set<std::string> columns_without_lock = { "database", "name", "metadata_modification_time" };
-    for (const auto& column : header.getColumnsWithTypeAndName())
+    for (const auto & column : header.getColumnsWithTypeAndName())
     {
         if (columns_without_lock.find(column.name) == columns_without_lock.end())
             return true;