public void fill(Result result, String summaryClass) {
        if (summaryClass == null)
            summaryClass = PartialSummaryHandler.resolveSummaryClass(result);
        timer.sampleFill(nextIndex(), context.getDetailedDiagnostics());
        Searcher current = (Searcher)next(); // TODO: Allow but skip processors which are not searchers
        if (current == null) return;

        try {
            nextProcessor();
            onInvokingFill(current, summaryClass);
            current.ensureFilled(result, summaryClass, this);
        }
        finally {
            previousProcessor();
            onReturningFill(current, summaryClass);
            timer.sampleFillReturn(nextIndex(), context.getDetailedDiagnostics(), result);
        }
    }
Calls fill on the next searcher in this chain. If there is no next, nothing is done.
container-search/src/main/java/com/yahoo/search/searchchain/Execution.java