Function assertFragmentSerializable

src/Processors/QueryPlan/QueryPlan.cpp:55–71

A stage fragment is shipped to workers by serializing its query plan, so every step must support serialization. Check up front (without serializing) so an unsupported plan fails early with a clear message instead of late, mid-execution, with a generic error.

/// serialization. Check up front (without serializing) so an unsupported plan fails early with a clear
/// message instead of late, mid-execution, with a generic error.
void assertFragmentSerializable(const QueryPlan & fragment, const String & stage_name)
{
    std::vector<const QueryPlan::Node *> stack;
    if (fragment.getRootNode())
        stack.push_back(fragment.getRootNode());
    while (!stack.empty())
    {
        const auto * node = stack.back();
        stack.pop_back();
        if (node->step && !node->step->isSerializable())
            throw Exception(ErrorCodes::SUPPORT_IS_DISABLED,
                "make_distributed_plan cannot distribute this query: step '{}' in stage '{}' is not "
                "serializable for remote execution", node->step->getName(), stage_name);
        for (const auto * child : node->children)
            stack.push_back(child);
    }
}

}