Added comment

src/Dictionaries/getDictionaryConfigurationFromAST.cpp

@@ -403,6 +403,8 @@ void buildConfigurationFromFunctionWithKeyValueArguments(
             auto function = builder->build({});
             function->prepare({});
 
+            /// We assume that function will not take arguments and will return constant value like tcpPort or hostName
+            /// Such functions will return column with size equal to input_rows_count.
             size_t input_rows_count = 1;
             auto result = function->execute({}, function->getResultType(), input_rows_count);