@Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((fields == null)
                ? 0
                : fields.hashCode());
        return result;
    }
Cache the positions of the fields.
stroom-core-shared/src/main/java/stroom/statistics/impl/hbase/shared/StroomStatsStoreEntityData.java