private Results<Target, ErrorMessage> resolveSearchChains(Collection<SearchChainInvocationSpec> prunedTargets,
                                                              SearchChainRegistry registry) {
        Results.Builder<Target, ErrorMessage> targetHandlers = new Results.Builder<>();

        for (SearchChainInvocationSpec target: prunedTargets) {
            Chain<Searcher> chain = registry.getChain(target.searchChainId);
            if (chain == null) {
                targetHandlers.addError(ErrorMessage.createIllegalQuery("Could not find search chain '" 
                                                                        + target.searchChainId + "'"));
            } else {
                targetHandlers.addData(new StandardTarget(target, chain));
            }
        }

        return targetHandlers.build();
    }
Returns true if we are requested to keep executing a target longer than we're waiting for it.
This is useful to populate caches inside targets.
container-search/src/main/java/com/yahoo/search/federation/FederationSearcher.java