private void setMaxFlushed(ProtonConfig.Builder builder) {
        // maxflushed should be moved down to proton
        double concurrency = builder.feeding.build().concurrency();
        if (concurrency > defaultFeedConcurrency) {
            int maxFlushes = (int)Math.ceil(4 * concurrency);
            builder.index.maxflushed(maxFlushes);
        }
    }
Translates group ids to continuous 0-base "row" id integers
config-model/src/main/java/com/yahoo/vespa/model/content/ContentSearchCluster.java