Method buildMongoDBQuery

src/Storages/StorageMongoDB.cpp:491–633

}

bsoncxx::document::value StorageMongoDB::buildMongoDBQuery(const ContextPtr & context, mongocxx::options::find & options, const SelectQueryInfo & query, const Block & sample_block)
{
    document projection{};
    for (const auto & column : sample_block)
        projection.append(kvp(column.name, 1));

    LOG_DEBUG(log, "MongoDB projection has built: '{}'", bsoncxx::to_json(projection));
    options.projection(projection.extract());

    bool throw_on_error = context->getSettingsRef()[Setting::mongodb_throw_on_unsupported_query];

    if (!context->getSettingsRef()[Setting::allow_experimental_analyzer])
    {
        if (throw_on_error)
            throw Exception(ErrorCodes::NOT_IMPLEMENTED, "MongoDB storage does not support 'enable_analyzer = 0' setting");
        return make_document();
    }

    const auto & query_tree = query.query_tree->as<QueryNode &>();

    if (throw_on_error)
    {
        if (query_tree.hasHaving())
            throw Exception(ErrorCodes::NOT_IMPLEMENTED, "HAVING section is not supported. You can disable this error with 'SET mongodb_throw_on_unsupported_query=0', but this may cause poor performance, and is highly not recommended");
        if (query_tree.hasGroupBy())
            throw Exception(ErrorCodes::NOT_IMPLEMENTED, "GROUP BY section is not supported. You can disable this error with 'SET mongodb_throw_on_unsupported_query=0', but this may cause poor performance, and is highly not recommended");
        if (query_tree.hasWindow())
            throw Exception(ErrorCodes::NOT_IMPLEMENTED, "WINDOW section is not supported. You can disable this error with 'SET mongodb_throw_on_unsupported_query=0', but this may cause poor performance, and is highly not recommended");
        if (query_tree.hasPrewhere())
            throw Exception(ErrorCodes::NOT_IMPLEMENTED, "PREWHERE section is not supported. You can disable this error with 'SET mongodb_throw_on_unsupported_query=0', but this may cause poor performance, and is highly not recommended");
        if (query_tree.hasLimitBy())
            throw Exception(ErrorCodes::NOT_IMPLEMENTED, "LIMIT BY section is not supported. You can disable this error with 'SET mongodb_throw_on_unsupported_query=0', but this may cause poor performance, and is highly not recommended");
    }

    auto on_error = [&] (const auto * node)
    {
        /// Reset limit, because if we omit ORDER BY, it should not be applied
        options.limit(0);

        if (throw_on_error)
            throw Exception(ErrorCodes::NOT_IMPLEMENTED,
                "Only simple queries are supported, failed to convert expression '{}' to MongoDB query. "
                "You can disable this restriction with 'SET mongodb_throw_on_unsupported_query=0', to read the full table and process on ClickHouse side (this may cause poor performance)", node->formatASTForErrorMessage());
        LOG_WARNING(log, "Failed to build MongoDB query for '{}'", node ? node->formatASTForErrorMessage() : "<unknown>");
    };

    const ConstantNode * limit = nullptr;
    const ConstantNode * offset = nullptr;

    if (query_tree.hasLimit())
    {
        limit = query_tree.getLimit()->as<ConstantNode>();
        if (!limit)
        {
            on_error(query_tree.getLimit().get());
        }
    }