Method executeSubquery

src/Interpreters/InterpreterParallelWithQuery.cpp:123–162

void InterpreterParallelWithQuery::executeSubquery(ASTPtr subquery, ContextMutablePtr subquery_context)
{
    auto query_io = executeQuery(subquery->formatWithSecretsOneLine(), subquery_context, QueryFlags{ .internal = true }).second;

    auto & pipeline = query_io.pipeline;

    if (!pipeline.initialized())
    {
        /// The subquery interpreter (called by executeQuery()) has already done all the work.
        return;
    }

    if (!pipeline.completed())
    {
        /// We allow only queries without input and output to be combined using PARALLEL WITH clause.
        String reason;
        if (pipeline.pushing() && pipeline.pulling())
            reason = "has both input and output";
        else if (pipeline.pushing())
            reason = "has input";
        else if (pipeline.pulling())
            reason = "has output";
        chassert(!reason.empty());

        if (subquery->getQueryKind() == IAST::QueryKind::Select)
            reason += " (Use UNION to combine select queries)";

        throw Exception(ErrorCodes::INCORRECT_QUERY,
                        "Query {} can't be combined with other queries using PARALLEL WITH clause because this query {}",
                        subquery->formatForLogging(), reason);
    }

    chassert(pipeline.completed());
    std::lock_guard lock{mutex};
    combined_pipeline.addCompletedPipeline(pipeline);

    io_holders.push_back(std::move(query_io));

    /// TODO: Special processing for ON CLUSTER queries and also for queries related to a replicated database is required.
}


void InterpreterParallelWithQuery::executeCombinedPipeline()