Method computeProjectionColumns

src/Analyzer/UnionNode.cpp:82–126

}

NamesAndTypes UnionNode::computeProjectionColumns() const
{
    if (recursive_cte_table)
        return recursive_cte_table->columns;

    std::vector<NamesAndTypes> projections;

    NamesAndTypes query_node_projection;

    const auto & query_nodes = getQueries().getNodes();
    projections.reserve(query_nodes.size());

    for (const auto & query_node : query_nodes)
    {
        if (auto * query_node_typed = query_node->as<QueryNode>())
            query_node_projection = query_node_typed->getProjectionColumns();
        else if (auto * union_node_typed = query_node->as<UnionNode>())
            query_node_projection = union_node_typed->computeProjectionColumns();

        projections.push_back(query_node_projection);

        if (query_node_projection.size() != projections.front().size())
            throw Exception(ErrorCodes::TYPE_MISMATCH, "UNION different number of columns in queries");
    }

    NamesAndTypes result_columns;

    size_t projections_size = projections.size();
    DataTypes projection_column_types;
    projection_column_types.resize(projections_size);

    size_t columns_size = query_node_projection.size();
    for (size_t column_index = 0; column_index < columns_size; ++column_index)
    {
        for (size_t projection_index = 0; projection_index < projections_size; ++projection_index)
            projection_column_types[projection_index] = projections[projection_index][column_index].type;

        auto result_type = getContext()->getSettingsRef()[Setting::use_variant_as_common_type]
            ? getLeastSupertypeOrVariant(projection_column_types)
            : getLeastSupertype(projection_column_types);
        result_columns.emplace_back(projections.front()[column_index].name, std::move(result_type));
    }

    return result_columns;
}

void UnionNode::removeUnusedProjectionColumns(const std::unordered_set<size_t> & used_projection_columns_indexes)
{