private void addLatency(long latencyMs, Metric.Context metricContext) {
        metric.set(QUERY_LATENCY_METRIC, (double) latencyMs, metricContext);
        metric.set(MEAN_QUERY_LATENCY_METRIC, (double) latencyMs, metricContext);
        metric.set(MAX_QUERY_LATENCY_METRIC, (double) latencyMs, 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