Method combineSubqueryOutputsToTuple

src/QueryPlan/QueryPlanner.cpp:2219–2244

}

RelationPlan QueryPlannerVisitor::combineSubqueryOutputsToTuple(const RelationPlan & plan, const ASTPtr & subquery)
{
    const auto & outputs = plan.getFieldSymbolInfos();

    if (outputs.size() > 1)
    {
        auto subquery_type = analysis.getExpressionType(subquery);
        const auto & type_tuple = typeid_cast<const DataTypeTuple &>(*subquery_type);
        ASTs tuple_func_args(outputs.size());
        std::transform(
            outputs.begin(), outputs.end(), tuple_func_args.begin(), [](auto & out) { return toSymbolRef(out.getPrimarySymbol()); });

        ASTPtr tuple_func_expr = makeASTFunction("tuple", std::move(tuple_func_args));
        if (type_tuple.haveExplicitNames())
            tuple_func_expr = makeCastFunction(tuple_func_expr, subquery_type);
        auto tuple_func_symbol = context->getSymbolAllocator()->newSymbol(tuple_func_expr);
        Assignments assignments{{tuple_func_symbol, tuple_func_expr}};
        NameToType types{{tuple_func_symbol, subquery_type}};
        auto old_root = plan.getRoot();
        auto expression_step = std::make_shared<ProjectionStep>(old_root->getCurrentDataStream(), assignments, types);
        auto new_root = old_root->addStep(context->nextNodeId(), std::move(expression_step));

        return {new_root, FieldSymbolInfos{{tuple_func_symbol}}};
    }
    return plan;
}

RelationPlan QueryPlannerVisitor::planSetOperation(ASTs & selects, ASTSelectWithUnionQuery::Mode union_mode)
{