bool checkCachedFailure(Step::ptr step, Connection & conn);

        /* If any step has an unsupported system type, then fail the
           build. */
        bool allSupported = true;

        /* If any step has an unsupported system type or has a
           previously failed output path, then fail the build right
           away. */
        bool badStep = false;

            BuildStatus buildStatus = bsSuccess;
            BuildStepStatus buildStepStatus;

                allSupported = false;

                pqxx::work txn(conn);

                buildStatus = bsUnsupported;
                buildStepStatus = bssUnsupported;
            }
            if (checkCachedFailure(r, conn)) {
                printMsg(lvlError, format("failing build %1% due to previous failure") % build->id);
                buildStatus = step == r ? bsFailed : bsFailed;
                buildStepStatus = bssFailed;
            }
            if (buildStatus != bsSuccess) {

                pqxx::work txn(conn);

                    ("update Builds set finished = 1, busy = 0, buildStatus = $2, startTime = $3, stopTime = $3 where id = $1")

                    ("update Builds set finished = 1, busy = 0, buildStatus = $2, startTime = $3, stopTime = $3, isCachedBuild = $4 where id = $1")

                    ((int) bsUnsupported)
                    (now).exec();
                createBuildStep(txn, now, build, r, "", bssUnsupported);

                    ((int) buildStatus)
                    (now)
                    (buildStatus != bsUnsupported ? 1 : 0).exec();
                createBuildStep(txn, now, build, r, "", buildStepStatus);

                badStep = true;

        if (!allSupported) continue;

        if (badStep) continue;

    bool cachedFailure = false;
    {
        pqxx::work txn(*conn);
        for (auto & path : outputPaths(step->drv))
            if (!txn.parameterized("select 1 from FailedPaths where path = $1")(path).exec().empty()) {
                cachedFailure = true;
                break;
            }
    }

    bool cachedFailure = checkCachedFailure(step, *conn);

}
bool State::checkCachedFailure(Step::ptr step, Connection & conn)
{
    pqxx::work txn(conn);
    for (auto & path : outputPaths(step->drv))
        if (!txn.parameterized("select 1 from FailedPaths where path = $1")(path).exec().empty())
            return true;
    return false;