receiver jobsetSharesChanged(*conn, "jobset_shares_changed");

        if (jobsetSharesChanged.get()) {
            printMsg(lvlTalkative, "got notification: jobset shares changed");
            processJobsetSharesChange(*conn);
        }

    auto jobsets_(jobsets.lock());

    auto i = jobsets_->find(p);
    if (i != jobsets_->end()) return i->second;

    {
        auto jobsets_(jobsets.lock());
        auto i = jobsets_->find(p);
        if (i != jobsets_->end()) return i->second;
    }

    if (shares == 0) shares = 1;

    auto jobset = std::make_shared<Jobset>(shares);

    auto jobset = std::make_shared<Jobset>();
    jobset->setShares(shares);

    auto jobsets_(jobsets.lock());
    // Can't happen because only this thread adds to "jobsets".
    assert(jobsets_->find(p) == jobsets_->end());

void State::processJobsetSharesChange(Connection & conn)
{
    /* Get the current set of jobsets. */
    pqxx::work txn(conn);
    auto res = txn.exec("select project, name, schedulingShares from Jobsets");
    for (auto const & row : res) {
        auto jobsets_(jobsets.lock());
        auto i = jobsets_->find(std::make_pair(row["project"].as<string>(), row["name"].as<string>()));
        if (i == jobsets_->end()) continue;
        i->second->setShares(row["schedulingShares"].as<unsigned int>());
    }
}

    Jobset(unsigned int shares) : shares(shares) { }

    std::atomic<unsigned int> shares;

    std::atomic<unsigned int> shares{1};

    }
    void setShares(int shares_)
    {
        assert(shares_ > 0);
        shares = shares_;

    void processJobsetSharesChange(Connection & conn);

    check schedulingShares > 0,

#ifdef POSTGRESQL

create function notifyJobsetSharesChanged() returns trigger as 'begin notify jobset_shares_changed; return null; end;' language plpgsql;
create trigger JobsetSharesChanged after update on Jobsets for each row
  when (old.schedulingShares != new.schedulingShares) execute procedure notifyJobsetSharesChanged();
#endif

create function notifyJobsetSharesChanged() returns trigger as 'begin notify jobset_shares_changed; return null; end;' language plpgsql;
create trigger JobsetSharesChanged after update on Jobsets for each row
  when (old.schedulingShares != new.schedulingShares) execute procedure notifyJobsetSharesChanged();
alter table Jobsets add constraint jobsets_check check (schedulingShares > 0);