Method processQuery

src/Server/HTTPHandler.cpp:466–852

void HTTPHandler::processQuery(
    ContextMutablePtr context,
    HTTPServerRequest & request,
    HTMLForm & params,
    HTTPServerResponse & response,
    Output & used_output,
    std::optional<CurrentThread::QueryScope> & query_scope)
{
    using namespace Poco::Net;

    LOG_TRACE(log, "Request URI: {}", request.getURI());
    std::string tenant_id = params.getParsed<std::string>("tenant_id", "");
    std::string database = request.get("X-ClickHouse-Database", "");
    if (database.empty())
        database = params.getParsed<std::string>("database", "");

    if (auto pos = database.find('`'); pos != String::npos)
    {
        //CNCH multi-tenant default database pattern from gateway client: {tenant_id}`{default_database}
        //Even this is a GET request or with "readonly=1" setting, we force to apply the tenant_id setting change.
        auto tenant_id_from_db = String(database.c_str(), pos);
        if (tenant_id.empty())
            tenant_id = tenant_id_from_db;
        else if (tenant_id != tenant_id_from_db && !tenant_id_from_db.empty())
            throw Exception("tenant id " + tenant_id + " from setting doesn't match tenant id from database " + tenant_id_from_db, ErrorCodes::UNKNOWN_USER);

        ///multi-tenant default database storage pattern: {tenant_id}.{database}
        if (pos + 1 != database.size())
        {
            auto sub_str = database.substr(pos + 1);
            if (sub_str == "default" || sub_str == "system")
                database = std::move(sub_str);
            else
                database[pos] = '.';
        }
        else                                     /// {tenant_id}`
            database.clear();
    }

    if (!database.empty())
        context->setCurrentDatabase(database);

    if (!tenant_id.empty())
    {
        context->setSetting("tenant_id", tenant_id);
        context->setTenantId(tenant_id);
    }

    if (!authenticateUser(context, request, params, response))
        return; // '401 Unauthorized' response with 'Negotiate' has been sent at this point.

    /// The user could specify session identifier and session timeout.
    /// It allows to modify settings, create temporary tables and reuse them in subsequent requests.

    std::shared_ptr<NamedSession> session;
    String session_id;
    bool session_is_set = params.has("session_id");
    const auto & config = server.config();