Function formatSetPretty

src/Processors/QueryPlan/QueryPlanFormat.cpp:237–303

        }

        String formatSetPretty(
            const ActionsDAG::Node * set_node,
            std::unordered_map<FutureSet::Hash, String, PreparedSets::Hashing> & subquery_set_names)
        {
            static constexpr size_t MAX_SET_ELEMENTS_TO_SHOW = 10;

            if (!set_node->column)
                return trimColumnIdentifier(set_node->result_name);

            const ColumnSet * column_set = typeid_cast<const ColumnSet *>(&set_node->column->getDataColumn());

            if (!column_set || !column_set->getData())
                return trimColumnIdentifier(set_node->result_name);

            FutureSetPtr future_set = column_set->getData();

            if (const auto * from_storage = typeid_cast<const FutureSetFromStorage *>(future_set.get()))
            {
                if (auto storage_id = from_storage->getStorageID())
                    return storage_id->getFullNameNotQuoted();
                return trimColumnIdentifier(set_node->result_name);
            }

            if (typeid_cast<const FutureSetFromSubquery *>(future_set.get()))
            {
                auto [it, inserted] = subquery_set_names.try_emplace(
                    future_set->getHash(),
                    fmt::format("subquery{}", subquery_set_names.size() + 1));
                return it->second;
            }

            if (auto * from_tuple = typeid_cast<FutureSetFromTuple *>(future_set.get()))
            {
                Columns key_columns = from_tuple->getKeyColumns();
                if (key_columns.empty())
                    return trimColumnIdentifier(set_node->result_name);

                size_t num_rows = key_columns[0]->size();
                size_t num_keys = key_columns.size();
                size_t to_show = std::min(num_rows, MAX_SET_ELEMENTS_TO_SHOW);

                String result = "(";
                for (size_t row = 0; row < to_show; ++row)
                {
                    if (row > 0)
                        result += ", ";
                    if (num_keys > 1)
                        result += "(";
                    for (size_t col = 0; col < num_keys; ++col)
                    {
                        if (col > 0)
                            result += ", ";
                        Field value;
                        key_columns[col]->get(row, value);
                        result += applyVisitor(FieldVisitorToString(), value);
                    }
                    if (num_keys > 1)
                        result += ")";