Method read

src/QueryPipeline/RemoteQueryExecutor.cpp:536–566

RemoteQueryExecutor::ReadResult RemoteQueryExecutor::read()
{
    if (!sent_query)
    {
        sendQuery();

        /// `connections` stays null if sendQuery() was cancelled before sending,
        /// so guard the dereference below (as every other use of it does).
        {
            LockAndBlocker lock(was_cancelled_mutex);
            if (was_cancelled)
                return ReadResult(Block());
        }

        if (context->getSettingsRef()[Setting::skip_unavailable_shards] && (0 == connections->size()))
            return ReadResult(Block());
    }

    while (true)
    {
        LockAndBlocker lock(was_cancelled_mutex);
        if (was_cancelled)
            return ReadResult(Block());

        auto packet = connections->receivePacket();
        auto anything = processPacket(std::move(packet));

        if (anything.getType() == ReadResult::Type::Data || anything.getType() == ReadResult::Type::ParallelReplicasToken)
            return anything;
    }
}

RemoteQueryExecutor::ReadResult RemoteQueryExecutor::readAsync()
{