Function addConvertingActions

src/Processors/QueryPlan/ReadFromRemote.cpp:91–119

}

static void addConvertingActions(Pipe & pipe, const Block & header, const ContextPtr & context, bool use_positions_to_match = false)
{
    if (blocksHaveEqualStructure(pipe.getHeader(), header))
        return;

    auto match_mode = use_positions_to_match ? ActionsDAG::MatchColumnsMode::Position : ActionsDAG::MatchColumnsMode::Name;

    auto get_converting_dag = [mode = match_mode, context](const Block & block_, const Block & header_)
    {
        /// Convert header structure to expected.
        /// Also we ignore constants from result and replace it with constants from header.
        /// It is needed for functions like `now64()` or `randConstant()` because their values may be different.
        return ActionsDAG::makeConvertingActions(
            block_.getColumnsWithTypeAndName(),
            header_.getColumnsWithTypeAndName(),
            mode,
            context,
            true);
    };

    if (use_positions_to_match)
        pipe.addSimpleTransform([](const SharedHeader & stream_header) { return std::make_shared<MaterializingTransform>(stream_header); });

    auto convert_actions = std::make_shared<ExpressionActions>(get_converting_dag(pipe.getHeader(), header));
    pipe.addSimpleTransform([&](const SharedHeader & cur_header, Pipe::StreamType) -> ProcessorPtr
    {
        return std::make_shared<ExpressionTransform>(cur_header, convert_actions);
    });
}

static void enableMemoryBoundMerging(QueryProcessingStage::Enum stage, const ClusterProxy::SelectStreamFactory::Shards * shards, Context & context)
{