private void incrErrorCount(Result result, Metric.Context metricContext) {
        metric.add(FAILED_QUERIES_METRIC, 1, metricContext);

        if (result == null) // the chain threw an exception
            metric.add(ContainerMetrics.ERROR_UNHANDLED_EXCEPTION.baseName(), 1, metricContext);
    }
Generate statistics for the query passing through this Searcher
1) Add 1 to total query count
2) Add response time to total response time (time from entry to return)
3) .....
container-search/src/main/java/com/yahoo/prelude/statistics/StatisticsSearcher.java